BRE Alternating Tread Stair Design

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09/08/2012



Alternating treadstairsG M B Webber and R J Feeney

RJ Feeney is Consultant in ergonomics and design, RFA

Building Research

EstablishmentField Survey Report

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n t r oll ed C o p y .



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iii

Introduction 1

Survey methodology 1

Site survey 1

Postal survey 1

Telephone survey 2

Findings 2

Where installed 2

Users 2

Features of alternating tread stairs and main stairs 2

Alterations to loft stairs 4

User behaviour and opinions 4Steepness 4

Slipperiness 4

Difficulties 4

Handrails 5

Safety 5

Conclusions 6

Action following the study 7

Acknowledgements 7

References 7

AppendixA Contentsofsitequestionnaire 8

Contents


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iv

Appendix D Comments on difficulties and precautions

on loft stairs 15

Difficulties in using loft stairs 15

Clothing 15

Carrying objects 15

Precautions 15

Appendix E Accidents on loft and main stairs 16

What happened on loft stairs 16

Number of steps fallen on loft stairs 16

Contributory factors with loft stairs 16Outcome of accidents on loft stairs 16

What happened on main stairs 16

Number of steps fallen on main stairs 16

Contributory factors with main stairs 17

Outcome of accidents on main stairs 17

Appendix F Specification of the geometry of

alternating tread stairs 18Introduction 18

Definitions 18

Design of straight flight stairs 19

Design A 19

Design B 20

Design C 20

Design of quarter turn stairs 21Design of half turn stairs 23

Appendix G Some design characteristics of

manufactured alternating tread stairs 25

Straight flight: 13 treads 25

Straight flight: 14 treads 25

Quarter turn: 13 treads 26Quarter turn: 14 treads 27

Half turn: 13 treads 29

Appendix H German and USA recommendations 30

German recommendations 30

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INTRODUCTION

This study of the use and safety aspects of stairs with

alternating treads was undertaken at the time of theDepartment of the Environment’s review in 1989 of the

Building Regulations 19851. There had been a trend in the

late 1980s for loft conversion design which incorporated a

flight of steps with alternating treads. Up to this time,

stairs for loft conversions needed to comply with the

requirements of the Building Regulations 1985 Approved

Document K2, but, in 1989, alternating t read stairs, which

would take up less space than normal stairs, were

introduced for installation in full loft conversions inEngland and Wales. Stairs of such shaped treads were of a

design which had not previously been used in the UK to

any great extent. In the absence of any existing specific

evidence about the safety and convenience of these stairs,

the purpose of the study was to obtain information on the

features of alternating tread stairs, users’ experience with

them, and their opinions on the ease of use, convenience

and safety of the stairs. Similar information was alsoobtained for the main stairs (ie stairs of normal design) in

the home to provide a common experience base on

which to assess any relative differences in the use of the

alternating tread stairs and the main stairs. Information

was gained through a survey of alternating tread stairs

installed in homes in England and Wales. At the same

time, a description of the geometry of alternating tread

stairs was developed by the first author to provide ameans of specifying the characteristics of such stairs.

Findings were provided to the Department of the

Environment for its consideration of the inclusion of

alternating tread stairs in the Approved Document. A

report by Webber and Feeney of some of the initial

findings of the survey was included in an Appendix3 to

the Department of Environment’s consultation in 1990

on Approved Document K: Safe means of access. The

main recommendations were later incorporated intoApproved Document K4. The purpose of this report is to

make the detailed findings known to a wider range of

professional bodies, designers and manufacturers,

building owners and user groups.

and which did not, and the frequency of use of the

stairs.

Section B sought to gain personal details of the main

respondent; for example eyesight difficulties, heightand shoe size, and problems they experienced such as

fear of heights and feelings of dizziness.

In section C the questions referred to both the main

and alternating tread stairs and sought information on

the frequency of use, the ease of use, the use of

handrails and their ease of use, accidents on the stairs,

feelings of security and safety on the stairs, the light ing

used, any improvement which could be made to the

stairs themselves and when they were installed. Section D listed the measurements to be made.

The contents of the site questionnaire are presented in

Appendix A.

Organisation of the three surveys was as fol lows.

Site survey

Letters were sent to the list of addresses provided by local

authority building control officers explaining the surveyand requesting an interview. After approximately five

days the recipients were telephoned to arrange a

convenient day and time for a home visit . However it was

found that a number of people were not l isted in the

directory or were ex-directory and, therefore, could not

be telephoned to arrange a visit . These people were sent a

second letter asking them to make a reverse charge call so

that arrangements could be made to visit them (only anegligible number did this). Other reasons for the poor

response included refusal to participate, and others had

left the address that was contacted, or had not had stairs

installed, or were in the process of having them installed.

Overall about 300 contacts were attempted resulting in

100 visits being arranged.

The survey involved visits to many geographical areas

including the Hounslow and Enfield areas of London,

Manchester, Leeds, Teesside, Leicestershire,Nottinghamshire, Northants, Surrey, Sussex, Kent and

Oxford, but the majority were in Hounslow and Enfield.

The response rate for the site survey was 30%, and was

just over 50% when the postal and telephone surveys

described below were included. There may be some bias

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questionnaire in the stamped envelope provided.

The contents of the postal questionnaire are presented

in Appendix B.

There were 27 returns.

Telephone survey

The questionnaire used was simi lar to that for the other

surveys but changed slightly to enable it to be fil led in

more easily and quickly by the interviewer. Twenty-five

interviews were conducted and they each took

12 minutes to complete.

The contents of the telephone questionnaire are

presented in Appendix B.The people who part icipated in the telephone survey

were those originally contacted about a visit but who

agreed that it would be uneconomic due to the distance

involved or the isolated location. A telephone call was

made either to carry out the interview there and then, or

to arrange a convenient t ime for call ing back.

FINDINGS

Where installed

Alternating tread stairs had been installed to provide

access to loft conversions. A number of households used

the loft space as a dual or mult i-purpose room, the most

common being study/ spare bedroom,

bedroom/ bathroom, bedroom/ shower/ study (Table 1).

The great majority of the stairs, nearly 60%, led to anextra bedroom. Office and guest/ spare room made up

another 30%. Other purposes included bath/ shower

room, playroom, sitting room, hobby room and store

room.

Of the stairs that were installed, 21% were in

bungalows and 78% between the first and second floors in

houses (Table 2). One installation was between the

second and third floors.

As all the alternating tread stairs had been installed forloft access, for simplification in this report alternating

tread stairs will also be referred to as loft stairs.

Users

In the 151 households surveyed it was estimated that the

75% having possessed them for more than 10 months

(Table 5).

The loft stairs were used between 1 and 12 times per

day compared with 7 to over 19 times per day for themain stairs. Table 6 shows the number of times the stairs

were used each day (a use up or down is counted as one

use). However, because the main stairs gave access to a

larger number of rooms on the first floor compared with a

room or rooms in the loft , the main stairs were used about

twice as frequently as the loft stairs.

All types of people used loft stairs and, although they

were to some extent a self-selected group, there were no

grounds for considering them as a special group. In themain they used the loft stairs daily, but obviously not as

frequently as the main stairs.

Features of alternating tread stairs and main stairs

One manufacturer had made about 50% of the installed

loft stairs.

The design of the majority, 67%, of the loft stairs

consisted of a single straight flight while another 30% hada quarter or half turn between flights; most of these were

quarter turn (Table 7). Other designs included a winder

and a spiral. Table 8 shows that most loft stairs, 79%, had

13 or 14 risers and 59% had open risers. Closed risers

were typically closed by a sloping board joining the rear

edge of each step (Table 9).

Wi th the main stairs, however, there was a smaller

number of straight flights, 26%, compared with flightshaving a quarter or half turn, 46%, or with a winder, 28%.

Stairs that had 13 or 14 risers comprised 61% of the total.

Only 5% of the main stairs had open risers.

The loft stairs included designs with a central

supporting beam or with str ings on both sides. Although

there were a number of di fferent manufacturers of loft

stairs, the shapes of the alternating treads were similar

(Figure 1). In some cases all the treads (including the top

tread abutting the landing) were the same shape but inother cases the top tread/ landing nosing was straight

and, therefore, was of a different shape to the other

nosings in the flight.

Methods of measurement and calculation of pi tch (θ),

‘going’ (G ) – the distance from one tread to the second

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projection. Additionally in a few cases the treads were

found to slope across the width of the stairs or between

front and back. In many instances the depth of the tread

and the rise of the top or bot tom step differedconsiderably from the other steps. A general difficulty

was that measurements were often carried out under

poor light condit ions and may have had to be made over

carpet.

In view of the above factors, it is estimated that the

linear dimensions could only be measured to about

±3 mm and angles to about ±1°. The combined errors

could account for up to about 3° difference between the

calculated and the measured pitch of a flight.Figures 4 to 11 are photographs of installed alternating

tread stairs showing examples of the various types of

design: central support ing beam or strings on both sides;

straight stairs or stairs with a quarter turn landing;

different shapes of top step; open or closed risers; and

one or two handrails.

Summaries of measurements and calculations are

presented in Tables 10 and 11 for alternating tread andmain stairs respectively.

The frequency distribution of different depths of tread

are shown in Table 12 f or the longer side (T 1) and Table 13

for the shorter side (T 2). For the longer side, 53% of the

depths were 260 mm or more; for the shorter side, 59% of

the depths were 150 mm or more.

The measured pitch of the stairs differed considerably

between loft and main (Table 14). Pitches of the loft stairs

were between 54°and 72°with 88% of these being 63° or

below. Measured pitches of the main stairs were between

36°and 49°.

The goings of the loft stairs ranged from 145 mm to

270mm (Table 15). Of these 71% had goings of 220 mm or

less. The rises ranged from 185 mm to 235 mm wi th 96%

having rises of 220 mm or less(Table 16). More detailed

measurements on a 14% sample of the loft stairs showed

that there can be substantial variations in pitch, going andrise between treads in a flight. Some of the top treads had

less depth of t read than other t reads in flights because of

different shapes(Figure 8). In some cases treads were not

level and sloped in the direction of t ravel or across the

width. In 5% of stairs, treads moved when walked on.

support ing beam or side str ings and fixed size of tread,

the nature of the projection depends upon the pitch of the

stairs.

In some cases the going was greater than the depth of tread, thereby creating a horizontal ‘gap’. This gap is at a

posit ion where the back of the heel of a shoe would land.

There were 6 cases of gaps, 2 cases involving Design A

and 4 cases Design B.

In comparison with the loft stairs, the goings on all

treads of the main stairs ranged from 180 mm to 260 mm

(Table 15) with 45% having goings of 220 mm or more.

The rises ranged from 160 mm to 220 mm (Table 16).

The majority of the loft stairs, 94%, had a varnishedwood surface(Table 19). Another 5% were carpeted. In

comparison, 96% of the main stairs were carpeted.

Width of treads of loft stairs, given in Table 20,ranged

from 530 mm to 870 mm wi th 71% of the widths being

610 mm or more.

Two handrails were much more common wi th loft

stairs, 65%, than with main stairs, 9% (Table 21).

The width between the handrails (or whereappropriate between the handrail and the opposing wall)

was considerably different for the loft and main stairs.

From Table 22 it is seen that the majority of main stairs,

over 71%, had a clearance width of 750 mm or more while

the majority, 75%, of loft stairs provided a clearance

width of 600 mm or more.

The handrail height above the pitchline of the stairs

(measured to the top of the handrail ) was, in general,

higher for loft stairs than for main stairs (Table 23). In the

case of the loft stairs, 22% were between 750 mm and

849mm, 52% between 850 mm and 999 mm, and 11%

were 1000 mm or more. With main stairs, 52% of

handrails were between 750 mm and 849 mm, 23% were

between 850 mm and 999 mm, and 4% were 1000 mm or

more. The differences between the heights of handrails

on loft and main stairs may be due to loft stairs being

installed more recently and perhaps conforming to moreup-to-date recommendations.

Whether handrails extended beyond the top or

bottom steps was recorded in the site survey (Table 24).

Extensions of handrails were more common on loft stairs.

For loft stairs, 71% of handrails extended beyond the top

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more in 65% and 82% of the main and loft stairs

respectively.

The most frequent types of infil l between the handrails

and stairs on the loft stairs were solid infill , 44%, andsloping planks, 40%(Table 28). For the main stairs, the

most frequent infil ls were solid, 38%, and vert ical rails,

35%, followed by sloping planks, 21%.

For landings on loft stairs(Table 29), the most frequent

types of infi ll of balustrades were solid, 47%, and vert ical

rails, 44%; for main stairs, vertical rails were most

frequent, 46%, followed by solid, 37%.

The headroom clearance (Table 30) for the loft stairs

varied considerably, ranging from 1400 mm to over4000mm. Of the measured clear headrooms, 53% were

2000 mm or more. The height of the 95th percenti le adult

male5 (unshod) is 1855 mm, and 41% of the headrooms

measured were below this figure.

Light ing was used on stairs as required, day or night .

The lighting on the loft stairs was assessed by the

interviewers as unsatisfactory in 7% of the installations.

Alterations to loft stairs

In 25 installations of loft stairs, alterations had been

carried out (Appendix C); the most common alteration

being to the handrail (6 added, 2 lowered and 2 removed,

1 changed in shape, 1 increased clearance and 1 reduced

clearance). Other alterations included tightening bolts

(3), adding (1) or removing (2) a sloping backing board,

carpeting treads (2), fixing non-slip strips to treads (2)

and having a platform built at the bottom of the stairs.

Information from other enquiries also revealed a few

cases where the owner had removed the alternating t read

stairs altogether.

USER BEHAVIOUR AND OPINIONS

Earlier studies of stairs use and accidents by BRE, Carson

et al6 in the USA, Hay and Barkow7 in Canada, andHeimplaetzer et al8 in the Netherlands, have identified a

number of ways of using stairs and contributory factors in

stairs accidents in the home. None of the studies included

alternating tread stairs. Factors considered to increase

accident risk include the type of footwear, wearing long

Slipperiness

The loft stairs were felt to be slippery by 72% of

respondents compared with 12% who thought their main

stairs were slippery. Almost all of the loft stairs had avarnished wood surface whereas main stairs had carpet.

Difficulties

People reported many more difficult ies in using the loft

stairs compared with the main stairs. These difficulties

related mainly to carrying objects up and down stairs;

70% of people reported difficulties on loft stairs compared

with 6% on main stairs (Appendix D). There was slightly

increased difficulty when wearing long or tight clothes, orwith certain types of footwear on loft stairs compared

with main stairs. While users would normally have

needed to take extra care in locating their feet on the

steps of loft stairs, when carrying larger objects this was

more difficult i f the objects prevented the users from

seeing the steps in front of them. Part icular objects

mentioned were vacuum cleaners, trays of drinks,

suitcases and children. Because the steps of loft stairswere narrower, this also made carrying wide or bulky

objects difficult. Furthermore, it was difficult to carry

anything which required two hands.

Many users, 64% of respondents, needed to take

precautions when using the loft stairs which did not apply

to the main stairs. These included avoiding climbing the

stairs in stockinged feet, or wearing high heels or

slippery-soled slippers. As a precaution a few users came

down backwards or sideways, or used the treads instead

of the handrails to steady themselves when going up.

Over 35% of respondents considered that the loft stairs

were more difficult to use in either direction than their

main stairs(Table 32). With regard to ease of use and

direction of movement on the stairs (Table 33), 93%

considered the main stairs were easy to use in either

direction, but this dropped to 56% for loft stairs. Some

25% of loft users considered down was more difficult , 19%said up was more difficult.

People were asked to consider which section of their

stairs wasmore difficult: top, middle, bottom or none

(Table 34). For main stairs, some 80% considered that, for

either direction of movement, no section of the stairs was

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On main stairs, about 4% considered it difficult to turn

round, whereas on loft stairs a much higher proportion,

about 55%, considered it diff icult (Table 35). This is to be

expected because of the complex manoeuvres involved inturning on alternating tread stairs.

The majority of users also found with loft stairs that

they were slower when going up, 74%, and down, 55%,

than with their main stairs (Table 36). In a similar way

many more people reported difficulty in hurrying on the

loft stairs than the main stairs, 34% and 4% respectively

(Table 37).

HandrailsHandrails were used much more frequently with loft

stairs than with main stairs (Table 38). Stairs can have one

handrail or two handrails or no handrail . On main stairs

with one handrail , 33% of respondents normally used it

when going up and 37% when going down; where two

handrails were present, none of the relevant respondents

used both handrails when going up but 38% did so when

going down. For loft stairs, 78% of respondents normallyused the handrail, where one was fit ted, when going up

and 81% when going down; where two handrails were

fitted, 55% of respondents used both handrails when

going up and 61% when going down.

In rating the height of handrails (Table 39), all

respondents rated the handrail height for the main stairs

as about r ight; this reduced to 82% for loft stairs with

around 10% rating the height too high. As some 11% of

measured handrail heights on loft stairs were 1000 mm or

more (compared to only 4% on the main stairs) this may

indicate that preferred heights on loft stairs are below

1000 mm. Additional information from the postal and

telephone surveys(Table 40) indicated that heights on

loft stairs were considered too high for chi ldren in 30% of

cases. In 39% of handrail installations, handrail heights on

loft stairs ranged from 900 mm to 1000 mm.

Difficulties in grasping and holding handrails on loftstairs were reported by 9% of respondents. No difficulties

were reported for handrails on main stairs. A few

respondents commented negatively on the shapes of

handrails even though the shapes varied considerably.

improvements that were suggested included more stable

fixing of the stairs, tread and handrails; handrails of easily

grippable shape and greater clearance from walls;

intermediary landings; wider stairs; providing child gates;placing lighting so as not to throw shadows on the stairs;

and providing emergency l ighting.

Interviewers also assessed during visits whether there

were any other factors which were likely to impair the

safe use of loft stairs. In 8% of cases, articles were stored at

the bottom of the stairs or on quarter landings, and plants

were placed on the stairs. Figures10 and 11 show

examples of objects on or near the stairs.

A total of 41 accidents were reported as havingoccurred on the 151 loft stairs and 18 on the 85 main

stairs. Of the 24 people who had accidents on loft stairs in

the interview sample, 8 were children (6 males and

2 females) and 16 were adult (9 males and 7 females).

These accident numbers cannot be rigorously compared

because of incomplete exposure data relating to the total

number of uses (by all users) within a well defined time

period. However, while the reported accident numbersare similar, because of the greater overall usage of main

stairs compared to loft stairs there is strong indication of a

relatively greater r isk of accident per use on alternating

tread stairs than main stairs.

With both types of stairs, most of the accidents

involved falling down a number of steps as a result of

slipping; others involved missing their foot ing or tr ipping

(Appendix E).Many of the victims reported having

stockinged feet and rushing as causal factors. Only in the

case of loft stairs (2 instances) was carrying items cited as

a causal factor. Other contr ibutory factors in accidents on

the loft stairs were recently-pol ished treads and turning

round. On the loft stairs, 37 people fell when going down

and 4 when going up. Of those falling when going down,

22% fell 7 steps or more, 73% fell 2 to 6 steps, and 16% fell

one step or slipped but did not fall down any steps. The

ratio of 9:1 for down:up is much greater than 3:1 for mainstairs in the home found in studies by BRE (based on an

analysis of Home Accident Surveillance System data and

a BRE stairs accident survey) and in the study by

Heimplaetzer et al.

Only four of the accident vict ims required hospital

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turns, winders or spirals); stairs designs of A, B or C tread

projections (page 3,Appendix F and Figure 2); going;

rise; pitch; sizes of projections; and one or two handrails.

Statistical tests (χ

2

) of categories of accidents on loft stairsby these design features are not significant.

However, there is a tendency for loft stairs with

extreme characteristics – such as calculated pi tch over

67° (exemplif ied by case numbers 54 and 76 in Table 10)

and positive or negative projection of over 25 mm (case

numbers 14, 20 and 98) – to have been associated with an

accident. I t is noteworthy that cases 54 and 76 had goings

less than 200 mm, cases 76 and 98 had rises of over

220mm, and cases 14 and 20 had calculated pitches of less than 55°.

CONCLUSIONS

All types of people use loft stairs and, although they

may to some extent be a self-selected group, there are no

grounds for considering them as a special group. In the

main they use loft stairs daily, although obviously not asfrequently as the main stairs.

As was expected, for reasons of space economy,

alternating t read stairs (loft stairs) are steeper and most

are narrower than main domestic stairs. They have also

been installed with less headroom and feature two

handrails more commonly than with main stairs.

People found more difficulties in using loft stairs, rated

them as less safe, more slippery, and steeper, and took

more precautions when using them than with their main

stairs. While it may be argued that some of these factors

arose because the stairs were a new feature in the house,

the great majority had been installed for longer than

10 months.

For these reasons it is concluded that alternating t read

stairs present special problems when users are hurrying

or are turning to change direction. Users had difficulty

when carrying objects up and down alternating treadstairs, reasons for which have been discussed earl ier.

Large or awkwardly shaped objects increased the

difficulty.

The accident rates (ie the number of accidents per

100stairs) for normal and alternating tread stairs cannot

(between each tread) and going of 220 mm or more

(between alternate treads) leads to a maximum limit on

pitch of 63.5°. This upper limi t on pi tch is lower than the

67° considered to be of greater r isk and midway betweenUSA9 and German10 recommendations, 60.6°and 66°

respectively. It is considered that any further evidence on

stairs use and stairs characteristics such as going,

projection, rise, pitch, width and handrail height would

involve specific laboratory studies.

It is clear from this survey that people perceived their

use of alternating tread stairs as different to traditional

stairs in domestic premises and that the stairs are

constructed differently. Alternating tread stairs should betreated quite separately in terms of design standards and

limits given on their application (eg the situation vis-à-v is

ladders and stairs).

Part icular design recommendations for alternating

tread stairs are:

(a) The treads should be level, both in the direction of

travel and across the width. Suitable adjustment

mechanisms need to be provided which also fix the treadssecurely.

(b) Rises and goings within the flight should be

uniform. Rise should be 220 mm or less (between each

tread) and going should be 220 mm or more (between

alternate treads). Particular attention to the design and

installation is required to achieve uniformi ty. This should

include the shape and dimensions at top and bottom of

the stairs.

(c) Projection of a tread should not exceed 25 mm and

there should be no horizontal gaps at the rear edge of

treads on installed stairs.

(d) Where the stairs are likely to be used by children,

open risers should be constructed so that 100 mm

diameter sphere cannot pass through the open risers. A

sloping backing board joining the rear edge of the steps is

one means of achieving this.

(e) Treads should have slip resistant surfaces which arealso resistant to damage on erosion in use; this might

consist of an insert on the port ion of the tread on which

the feet are placed of suitable material to prevent slipping.

(f ) The constructed and installed stairs and handrails

should be stable and securely fixed.

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are likely to be used by children, guarding should be

constructed so that 100 mm sphere cannot pass through

any opening in the guarding.

(j) D imensions of intermediate landings should be

determined by the clear width of the stairs.

(k) The headroom measured as the minimum vertical

distance from the pitch line should not be less than

2000 mm unless this proves to be impracticable in loft

conversions.

(l ) The stairs should be suitably i lluminated by art ificial

lighting.

It is also recommended that manufacturers and

installers should provide information explaining theprecautions to be taken when using alternating tread

stairs including:

avoiding the wearing of tight clothing

avoiding the use of unsuitable footwear (eg slippers)

preventing their use by small chi ldren unless

supervised

avoiding their use by elderly or handicapped people

avoiding hurrying on the stairs avoiding turning on the stairs

avoiding carrying large or heavy objects, or objects

that require two hands

consider installation of a child gate

ACTION FOLLOWING THE STUDY

After consideration of the survey findings and other

consultations, the main recommendations were

incorporated into Approved Document K 1991.

Clauses 1.22 to 1.23 of Part K1 regarding alternating

tread stairs state that:

This type of stair is one of a number of stair types designed to

save space. The general pattern of steps has alternate handed

steps with part of the tread cut away; the user relies on

famil iari ty and regular use for reasonable safety (see diagram).Al ternating tread stairs should only be used in one or two

straight f lights for a loft conversion and then only when there is

not enough space to accommodate a stair satisfying para 1.1 to

1.17. It should only be used for access to one habitable room,

together if desired with a bathroom and/ or a WC. This WC

must not bethe only WC in the dwell ing

ACKNOWLEDGEMENTS

We wish to thank all those who took part in the survey.

REFERENCES

[1] Department of the Environment and the Welsh Office.The

Building Regulations 1985. Statutory Instrument 1985 No 1065.

London, HMSO, 1985.


Building Regulations 1985 Approved Document K: Stairs, ramps and

guards.London, HMSO, 1985.

[3] Department of the Environment and the Welsh Office.BuildingRegulations 1985: Approved Document K Safe means of access (Draft

Approved Document for public consultation): Appendix A Survey of

alternating tread stairs by G M B Webber and R J Feeney. London, DOE,

1990.


Building Regulations 1991 Approved Document K: Stairs, ramps and

guards (1992 edition). London, HMSO, 1991.

[5] Pheasant S.Bodyspace. Anthropometry, ergonomics and design.

London, Taylor and Francis. 1986.

[6] Carson D H, Archea J C, Margulis S T and Carson F E.Safety

on stairs. National Bureau of Standards Building Science Series 108.

USA, NBS, 1978.

[7] Hay T F and Barkow B.Personal and building factors in stair

safety. Accident reduction methods in homes, at work, and in public

places. A report prepared for Health and Welfare Canada, National

Research Council Canada, Public Works Canada and Supply and

Services Canada. Toronto, Behavioural Team, 1985.

[8] Heimplaetzer P V, Musson J H M M, Goosens L H J and

Clement R.Veiligheid van trappen in en bij woningen. Kenmerken vantrappen als risikofaktoren. Delft, Technische Universiteit Delft, 1987.

[9] National Fire Protection Association.Life Safety Code 1988.

Quincy (Mass., USA), NFPA, 1988.

[10] Berufsgenossenschaft für den Einzelhandel.Steiltreppe mit

wechselseitig verzogenen Stufen.Unfallschutz in Einzelhandel

ZH1/ 262: 1973. Bonn, Berufsgenossenschaft für den Einzelhandel,

1973.

[11] Feeney R J and Webber G M B.Safety aspects of handrail

design: a review. Building Research Establishment Report. Garston,BRE, 1994.

[12] British Standards Institution.Wood stairs. Specification for

stairs with closed risers for domestic use, including straight and winder

flights and quarter or half landings.British StandardBS 585:Part

1:1989. London, BSI, 1989.

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APPENDIX A

CONTENTS OF SITE QUESTIONNAIRERather than reproduce the questions in full, the following are abridged versions of those put to respondents.

Section A Users of stairs For answer by a main occupant of the house

1 Where do the loft stairs give access to?Identify rooms.

2 Who uses the loft stairs in your household?Sex, approximate age, frequency of use (1)(2)(3) and roomsused. (1) = Number/ day. (2) = Number/ week. (3) = Number/ month (Up and down = twice)

3 Do any of the users have a physical restriction? Eg walking difficulty, balance difficulty, generalweakness, poor co-ordination

4 Are there any members of the household who do not use the loft stairs?Sex, approximate age and reasonsfor non-use.

5 Are there any visitors who use the loft stairs?Response in same terms as question 2.

6 Are there any visitors to the house who do not use the loft stairs?Sex, approximate age and reason fornon-use.

If there was another adult in the household who used both main and loft stairs but experienced difficulties withone or other or both and who was available for interviewing, the remainder of the questionnaire was thenaddressed to that person.

Section B Personal details of respondent

7 When using main/ loft stairs, do you wear contact lenses?spectacles?

8 Do you have a fear of heights?

9 Do you ever feel dizzy?If yes, describe.

10 What is your height?

11 What is your shoe size?

Section C Respondent's performance on stairs The following questions referred to both the main and thep o w ell - will



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16 Do you normally use the left handrail going up?going down?neither?

17 Do you normally use the right handrail going up?going down?neither?

18 Do you find the height of the handrail on the left to be too high?about right? too low?

19 Do you find the height of the handrail on the right to be too high?about right?too low?

20 Do you have difficulty in grasping and holding the left handrail going up?going down?

21 Do you have difficulty in grasping and holding the right handrail going up?going down?

22 Do you have to take any other precautions whilst using the stairs? If yes, describe, giving reasons. Eg notwearing footwear, not going barefooted or in stocking feet, facing backwards going down the stairs.

23 How easy do you find it to use the loft stairs compared to the main stairs?Loft stairs more difficult, loft stairsless difficult, both just as easy.

24 How do you find going up and going down the stairs?Down more difficult, up more difficult, same up and

down.

25 Is the top, middle, bottom or none of the stairs relatively more difficult when going up?when going down?

26 Do you find the loft stairs slower, the same or faster than the main stairs going up?going down?

27 Have you ever needed to hurry or run on the stairs?If yes, did you have any difficulty and describe the event.

28 Have you ever needed to turn round when going up the stairs (eg in an emergency) and if so did you have

difficulty? Give details.

29 Have you ever needed to turn round when going down the stairs and if so did you have difficulty?Givedetails.

30 Have you ever found the steps slippery?If yes, give details.

31 How do you find the steepness of the stairs?Steep, just right, shallow.

32 Have you had any other di fficulties whi lst using the stairs? If yes, give details.

33 Have you or any member of your household ever had an accident on the stairs?If yes, give details: time of day; type of accident (eg slip, tripping over clothes, carrying item); personal factors (eg illness or disability);conditions (eg dark, wet shoes). If fell, indicate whether up or down, point at which fall commenced, how manysteps in fall. Who treated injuries: yourself? GP?hospital? other?

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38 Give details of any ways in which you feel the safety of the stairs could be improved.

39 If the loft stairs were already installed when you moved into the house, how long is it since you moved in?

40 If you had the loft stairs installed yourself, what was the date of the installation?

41 Have you made any alterations to the loft stairs?If yes, give details. Eg insertion or removal of handrails,carpeting etc.

42 If chi ldren use the loft stairs, how well do they manage to go up and down?

43 Were you given any instructions or warnings concerning the use of the loft stairs?

Section D Physical details of stairs The following questions referred to both the main and the loft stairs,and answers were sought for both

44 Draw a rough plan, with measurements, of the floor beneath the loft stairs and the location of the stairswithin the space.

45 Is the stairs design straight, dog leg, winder, spiral, curved or other? Describe the design.

46 Count the number of vertical risers.

47 Are the risers of the open or closed type?

48 What is the clear width of the treads of the loft stairs?

49 Measure from the front of the tread to the back of the tread on the longer side (see Figures 1 and 2).

50 Measure from the front of the tread to the back of the tread on the shorter side (see Figures 1 and 2).

51 Measure the projection of the shorter side of the tread beyond the longer side of a tread above it (see Figures1 and 2).

52 Measure the horizontal overlap of the tread on the tread below.

53 Measure from the surface of one tread to the surface of the tread above it (see Figure 2).

54 Measure the going of the main stairs (the going is the horizontal distance from the front of one nosing to thefront of the nosing of the stair above).

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60 What is the clear width between the handrails?

61 What is the dimension of the gap between the handrail and the adjacent wall?

62 What is the shape of the handrail? Eg round, oval, horizontal, vertical or other. Describe.

63 What are the dimensions of the handrail? Diameter, width and thickness.

64 Describe the type of 'fill ing' between the rail and the stairs. Eg vert ical rails, single sloping plank, solid orother. Describe.

65 Measure the distance between the floor at the base of the stairs to the floor at the top of the stairs.

66 For the loft stairs, measure the horizontal distance between the front of the nosing of the bottom tread andthe back of the top tread.

67 Using the formula D = (n – 1)K + T 1, calculate the horizontal distance between the front of the bottom tread

and the back of the top tread to confirm the measurement of question 65 (see Figure 3).

68 Measure vert ically from the pitchline to the ceiling and record the minimum value (see Figure 3).

69 For the loft stairs, using the formula tan θ = r / K , calculate the angle of the stairs to the horizontal (pitch).

70 If there is a landing on the stairs, what are the dimensions?

71 With a rough sketch indicate the posit ion of the balustrade at the top of the loft stairs.

72 Describe the type of 'fill ing' between the landing balustrade and the floor. Eg vertical rails, single horizontal

plank, solid or other.

73 Draw a rough plan, with dimensions, of the room(s) reached by the loft stairs and indicate their posit ion.

74 Are there any particular features of the stairs which are non-standard or unusual?

75 Is there anything about the stairs likely to impair their safety in use?Eg plants, frayed carpet, loose boards.Describe.

76 Assess the quality of lighting on the stairs in terms of location, level and direction of il lumination.

77 Count the number of storeys there are within the building and state between which the loft stairs aresituated.

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APPENDIX B

CONTENTS OF POSTAL AND TELEPHONE QUESTIONNAIRES

1 What is the model of the loft stairs and the name of its manufacturer?

2 Are your loft stairs straight? dog leg (turn sharply to left or right)?winder (curved)?spiral (stairs around acentral pillar)? other?

(a) Were they already installed when you moved in?(b) If yes, when did you move in?

(c) If no, how long have your stairs been installed (months)?

3 Have you made any alterations to your loft stairs? If yes, describe.

4 Do the stairs give access to main bedroom?guest bedroom?bathroom?office?sitting room?store room?other?(Tick more than one if necessary)

5 Give the main users of the loft stairs and the number of t imes a day the stairs are used. For each user:age, male/ female, and number of times a day used (Up and down = twice).

6 Is there anyone in the household who, for some reason, does not use the loft stairs?If yes, state who(referring to question 5) and explain the reason.

7 If you have regular visitors to the house who use the loft stairs, give age, male/ female.

8 Are there any visitors to the house who for some reason do not use the loft stairs?If yes, explain thereason.

9 Would you say that anyone has difficulty when going up your loft stairs?If yes, describe difficulty.

10 Would you say that anyone has difficulty when going down your loft stairs?I f yes, describe difficulty.

11 If the answer to question 9 is yes, which part of your loft stairs is considered to be relatively more difficultwhen going up?Top part, middle part, bottom part, none.

12 If the answer to question 10 is yes, which part of your loft stairs is considered to be relatively more difficult

when going down?Top part, middle part, bottom part, none.

13 Do any users have diff iculty in using the loft stairs when wearing long or restrictive clothing? Eg ankle-length tight skirt. If yes, state who (referring to answers to question 5).

14 Do any members of the household have difficulty carrying objects up or down the loft stairs?Eg vacuum cleaner tray of drinks load of washing If yes describep

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19 When going up your loft stairs, could users turn round and go back down?Not at all, with difficulty, easily.

20 When going down your loft stairs, could users turn round and go back up?Not at all, with difficulty, easily.

21 How many steps are there in your stairs?

22 Are the risers open or closed?

23 Looking up the stairs on which side is the handrail? Left, right, both sides, neither.

24 For an adult, is the height of the handrail(s) too high?just right? too low?

25 For a child, is the height of the handrail(s) too high? just right? too low?

26 Do any of the users find the handrail difficult to grip? If yes, explain why. Eg the shape is unsatisfactory,there is inadequate space between the handrail and the wall.

27 When going up, do users normally use one handrail?both handrails?neither handrail?

28 When going down, do users normally use one handrail?both handrails?neither handrail?

29 What is the fill ing between the rail and the stairs?Eg vertical rails, sloping plank(s), solid, other.

30 Do you consider the tread surface of your loft stairs to be slippery?

31 What is the tread covering?Eg wood, plastic, carpet, other.

32 Do the stairs have protective nosings? If yes, describe.

33 Compared to your main stairs, are your loft stairs steep?just right?shallow?

34 Has anyone had an accident on your loft stairs?If yes state who and give details. Eg fell up or down, numberof steps missed. Were they carrying anything?Did they slip or tr ip? Was the lighting satisfactory? Did theyrequire treatment by a doctor or hospital?

35 Compared to your main stairs, how safe do you feel on your loft stairs?Less safe, just as safe, more safe.

36 Are there any ways in which you feel the safety of the loft stairs could be improved?

37 What is the type of dwelling?House, bungalow, other.

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APPENDIX CALTERATIONS AND SUGGESTED IMPROVEMENTS TO LOFT STAIRS

Alterations25 respondents (17% of the total) had carried out the following alterations to their loft stairs:

added a handrail (6)tightened the bolts to make them more secure (3)removed a handrail (2)

lowered a handrail (2)carpeted the treads (2)fitted non-slip strips to the treads (2)removed backing boards to give more space on the treads for users' feet (2)people claimed to have had a platform built at the bottom of the stairs to make them less steep (2)reduced the gap between the handrail and the adjacent wall to make the stairs slightly wider (1)moved the stairs sideways to give more space to hold the handrail (1)changed the handrail from round to a sloping plank (1)added a backing board so that items could not be dropped through (1)

Suggested improvements79 respondents (52% of the total) thought the following improvements could be made (some respondents offeredmore than one suggestion):

fixing a non-slip surface to the treads (31). Specific suggestions made were:nosing strip (14)non-slip surface (10)carpeting (8)

making the pitch of the stairs less steep (21); though respondents were aware that this would take upmore space, they had chosen or were forced to install a steep design of stairs because of lack of space

providing always for two handrails (13); some respondents pointed out that the width of the stairs would stillhave to be adequate

fixing a backing board to the open risers (9)changing to a full conventional tread (4)making the stairs more stable (4); some rocked slightly when ascended or descendedshaping handrails so that they are easily gripped (2); ie round like a mop handlefitting more secure handrails (2)designing stairs that have a quarter or half turn landing, or a winder to make users concentrate and be less likely

to fall (2)designing stairs to be wider (2)designing stairs with deeper treads (1)fixing treads more securely (1)reducing the height of rises (1)

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APPENDIX DCOMMENTS ON DIFFICULTIES AND PRECAUTIONS ON LOFT STAIRS

Difficulties in using loft stairs23 respondents (15% of the total) reported that someone in their household did not use the loft stairs for thefollowing reasons:

too young (12)handicapped (5)

over 70 years old and had difficulty using the stairs (3)children were not allowed in their parents' or siblings' bedroom (2)no reason (1)

7 respondents reported that some people (particularly visitors) had difficulty using the stairs the first few timesor because they did not use them often

Clothing37 respondents (31% of the total) reported that they experienced difficulties using the main stairs and 53 (35%)

when using the loft stairs wearing certain clothing (eg a long dressing gown or tight skirt)

Carrying objects105 respondents (70% of the total) reported experiencing difficulty carrying objects up and down the loft stairscompared to 5 (site sample only) on the main stairs. These included the following reasons (some respondentsreported more than one difficulty):

when the object was a vacuum cleaner (33)carrying anything which required two hands (24)

carrying bulky objects (13)needing to hold one handrail (12)when the object was a tray of drinks (7)when the object was a suitcase, partly because of the width (4)when carrying items down it was not possible to see the steps (4)carrying any items on the stairs (3)carrying objects up the stairs because the stairs were excessively steep and they were not able to see

where to put their feet (2)when carrying items that put them off balance (1)carrying items on narrow stairs (1)carrying a child (1)no reason (3)

Precautions97 respondents (64% of the total) stated that they would take precautions with the type of footwear they would

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APPENDIX EACCIDENTS ON LOFT AND MAIN STAIRS

41 respondents reported accidents on their loft stairs.

What happened on loft stairsslipped (25)missed their footing (5)tripped (2)

no description (9)

Number of steps fallen on loft stairs37 people fell when going down the stairs:

fell 7 steps or more (8)fell 2 to 6 steps (27)fell one step, or slipped but did not fall down any steps (6)

4 people fell when going up the stairs

Contributory factors with loft stairsvictims were in stockinged feet (11)stairs had been polished just prior to the accident (2)victims were carrying items (2); one a quilt and one a vacuum cleanervictim turned round (1)victim heard the telephone ring (1)victim was not concentrating (1)

victim did not position feet properly (1)victim had flu (1)victim was pregnant (1)no contributory factor cited (20)

Outcome of accidents on loft stairstreated at home (10)went to hospital for a checkup, but nothing serious reported (2)did not require any treatment (29)

18 respondents reported accidents on their main stairs.

What happened on main stairsslipped (13)

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Contributory factors with main stairsvictims were in stockinged feet (2)

victims were rushing (2)victim was wearing slippers (1)victim was wearing wrong footwear (1)victim heard the telephone ring (1)victim tried to pick up an object (1)no contributory factor cited (10)

Outcome of accidents on main stairstreated at home (3)went to hospital for a checkup (2)did not require any treatment (13)

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APPENDIX FSPECIFICATION OF THE GEOMETRY OF ALTERNATING TREAD STAIRS

by G M B Webber

IntroductionThere is no existing British Standard specification for alternating tread stairs within the UK nor has theirgeometry been described. Therefore a general description of the geometry of alternating tread stairs wasdeveloped in order to categorise the types of stairs encountered in the survey.

Designs with straight flights and flights with quarter or half turn landings are considered. The geometry of spiral stairs designs and stairs with winders has been excluded due to their complexity.

In Germany these stairs have been referred to under Accident Prevention Regulations ZH 1/ 26210 since 1973,

and a specification has been introduced into the USA in the Life Safety Code9. These two specifications refer totwo different types of design of alternating tread stairs and, furthermore, refer to different designs to those beingintroduced into the UK. These other specifications are presented in more detail in Appendix H for referencepurposes.

The aim was to develop calculation methods which provide a systematic means of assessing the dimensionalcharacteristics of a wide range of manufactured alternating tread stairs. Thence to provide a means of sett ingrequirements, aiding the design of stairs and the checking of plans and related details. Equations have beendeveloped to calculate rise, going, pitch, length of stairs with straight flights, and quarter or half turn stairs.

DefinitionsThe type of shape of tread found in the survey is shown in Figure 1.

The following notation is used to define and calculate the dimensional characteristics of alternating tread stairs:

T 1 is the depth of tread; ie measured from the front of the tread to the back of the tread on the

longer side (in mm)T 2 is the depth of tread on the shorter side (in mm)

P is the horizontal projection of the nosing of the shorter side of a tread beyond the nosing of the longerside of the tread above it (in mm) as shown in Figures 1 and 2. P can have a positive value (nosing

protrudes) or negative (nosing retracted)

K is the horizontal distance (in mm) as shown in Figure 2G is the going (in mm) as shown in Figure 2. G has been defined in this manner to most closely

resemble the traditional use of the term 'going' but also takes into account which of the two (or both)nosings above project the foremost into the vertical plane to obstruct the lowering of a foot

Q is the going (in mm) of the first tread below the top landing in Design C as shown in Figure 2cθ is the pitch (in degrees)

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Design of straight flight stairsThe site survey revealed three basic types of design of stairs characterised by the projection of the nosing of the

intermediate tread (shorter side) P . The stairs are classified as follows:

Design A: P is positiveDesign B: P is zeroDesign C: P is negative

The geometrical description of these three types of design are presented in turn below.

Design A

In this design the constructional arrangement of the treads, shown in Figure 2a, is such that the nosing of theshorter side of an intermediate tread projects horizontally beyond the nosing of the longer side of the treadabove it; ie P is positive.

In Figure 2a, the three marked goings G are equal.

In this constructional arrangement:

K =

T 1 –

T 2 +

P (1)

G = 2K – P (2)

G = 2(T 1 – T 2) + P (3)

tan θ = r (4) --------

K

G + P = 2r (5) ----------------

tan θ

It is possible for G to be longer than the depth of tread T 1 thereby creating a horizontal gap. This should be

avoided, so that for G to be always equal to or less than T 1:

for G ≤ T 1

2K – P ≤ T 1 (6)

K ≤ T 1 + P (7) -----------------------

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D = (N – 1)r + T 1 (12) ---------------------------

tan θ

tan θ = (N – 1)r (13) ---------------------------

D – T 1

Clear headroom H is measured from the pitchline as shown in Figure 3.

The above equations are used to calculate the dimensional characteristics of a manufactured alternating tread

stairs consisting of a single straight flight (see Appendix G). The calculated dimensions agree very closely withthe manufacturer's li terature. Where P is positive, the designs are of type A.

Design BIn this design the constructional arrangement of the treads, shown in Figure 2b, is such that the nosing of theshorter side of an intermediate tread vertically aligns with the nosing of the longer side of the tread above it; ieP is zero.

In Figure 2b, the three marked goings G are equal.


K = T 1 – T 2 (14)

G = 2K (15)

G = 2(T 1 – T 2) (16)

tan θ = r (17) --------

K

G = 2r (18) ----------------

tan θ

In order to avoid a horizontal gap, such that G ≤ T 1, the following conditions should apply:

2K ≤ T 1 (19)

K ≤ T 1 (20) ---------

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K = T 1 – T 2 + P (21)

G = 2K (22)

G = 2(T 1 – T 2) + P (23)

Q = G – P (24)

Since P is negative, this means that Q > G as shown in Figure 2c:

tan θ = r (25) --------

K

G = 2r (26) ----------------

tan θ

Assuming that the top tread abuts the top landing, then equations (8) to (13) also apply to this design.

The above equations are used to calculate dimensions presented in Appendix G. Where P is negative, the designis of type C.

The type of construction of the manufactured stairs detailed in Appendix G uses a fixed length of mainsupporting string and cams on each tread enable treads to be levelled. With this type of construction, the lowestpitch will have maximum projection and, as the pitch is increased the treads overlap more, the projection passesthrough zero and onto a negative value. Hence for example in Appendix G for 13 treads, when K changes from

134 mm to 89 mm, a shift of 45 mm, P changes from 24 mm to –21 mm, a shift of 45 mm.

Design of quarter turn stairsQuarter turn alternating tread stairs are available and the survey included this type of design. In the examplewhich follows, an intermediate landing is fixed against the walls at a 90° turn. Additional notation is required

and a similar notation to that used for quarter turn winder stairs in BS 585:Part 112 is used here. Additionaldefinitions are:

N 1

is the number of alternating treads in lower straight flight

N 2 is the number of alternating treads in upper straight flight

a for the upper straight flight is the horizontal distance from top landing (back edge of top tread) to frontedge of bottom nosing (in mm)

b for the lower straight flight is the horizontal distance from the intermediate landing (rearmost frontedge of landing profile) to front edge of bottom nosing (in mm)i h h i l di f l di (b k d f d) ll (i ) h i Fip

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It can be seen that:

A = L a + a (27)

where a = (N 2 – 1)K + T 1 (28)

B = L b + b (29)

where b = (N 1 + 1)K (30)

r = H (31) ---------------------------------------------

N 1 + N 2 + 1

These equations, together with equations(1) to (5) when P is positive, and equations (21) to (26) when P isnegative, are used to calculate the space required for a range of quarter turn stairs; ie distances A and B (seeAppendix G). The calculated values are generally within a mm or so of the manufacturer's tabulated data.

B

Lb

La

a

A

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Design of half turn stairsHalf turn alternating tread stairs are available and the survey included this type of design. In this example, an

intermediate landing is fixed against the walls at a 180° turn. The following definitions and notation are used:

N 1 is the number of alternating treads in lower straight flight

N 2 is the number of alternating treads in upper straight flight

a for the upper straight flight is the horizontal distance from top landing (back edge of top tread) to frontedge of bottom nosing (in mm)

b for the lower straight flight is the horizontal distance from the intermediate landing (rearmost frontedge of landing profile) to front edge of bottom nosing (in mm)

A is the horizontal distance from top landing (back edge of top tread) to wall (in mm) as shown inFigure F2B is the horizontal distance from bottom tread (foremost front edged) to wall (in mm) as shown in

Figure F2L a is the length of the intermediate landing from the wall to the foremost front edge of the bottom nosing

of the upper flight (in mm) as shown in Figure F2L b is the length of the intermediate landing from the wall to the rearmost front edge of the intermediate

landing (in mm) as shown in Figure F2C is the length of the intermediate landing (in mm) as shown in Figure F2

It can be seen that:

A = L a + a (32)

where a = (N 2 – 1)K + T 1 (33)

B = L b + b (34)

where b = (N 1 + 1)K (35)

r = H (36) ---------------------------------------------

N 1 + N 2 + 1

These equations, together with equations (1) to (5) when P is positive, are used to calculate the space requiredfor a range of half turn stairs; ie distances A and B (see Appendix G).

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La

a

A

C

Lb

b

B

Figure F2Stairs with half turn


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APPENDIX G

SOME DESIGN CHARACTERISTICS OF MANUFACTURED ALTERNATING TREADSTAIRS

Straight flight: 13 treadsExample 1: T 1 = 260 mm, T 2 = 150 mm

_______________________________________________________________________________________________________________________________________________

Floor-to- Rise Distance Projection Distance Going Pitchfloor height (r ) (D ) (P ) (K ) (G ) (θ)(mm) (mm) (mm) (mm) (mm) (mm) (°)_______________________________________________________________________________________________________________________________________________

2800 215 1330 –21 89 178 67.52750 211 1430 –13 97 194 65.22700 208 1530 –4 106 212 63.02650 204 1620 3 113 223 60.9

2600 200 1700 10 120 230 59.02550 196 1770 16 126 236 57.32500 192 1870 24 134 244 55.1_______________________________________________________________________________________________________________________________________________

Straight flight: 14 treadsExample 2: T 1 = 260 mm, T 2 = 150 mm

_______________________________________________________________________________________________________________________________________________

Floor-to- Rise Distance Projection Distance Going Pitchfloor height (r ) (D ) (P ) (K ) (G ) (θ)(mm) (mm) (mm) (mm) (mm) (mm) (°)_______________________________________________________________________________________________________________________________________________

3000 214 1450 –18 92 184 66.82950 210 1550 –11 99 198 64.72900 207 1650 –3 107 214 62.72850 204 1740 4 114 224 60.82800 200 1820 10 120 230 59.02750 196 1890 15 125 235 57.42700 193 1960 21 131 241 55.9_______________________________________________________________________________________________________________________________________________


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Quarter turn: 13 treadsExample 3: floor-to-floor height = 2800 mm, T 1 = 260 mm, T 2 = 150 mm, rise = 215 mm, pitch = 67.5°,

projection = –21 mm, going = 178 mm

_______________________________________________________________________________________________________________________________________________

Stairs a L a b L b A B

classification* (mm) (mm) (mm) (mm) (mm) (mm)_______________________________________________________________________________________________________________________________________________

1/ L/ 11 1150 595 178 661 1745 839

2/ L/ 10 1061 595 267 661 1656 9283/ L/ 9 972 595 356 661 1567 10174/ L/ 8 883 595 445 661 1478 11065/ L/ 7 794 595 534 662 1389 11966/ L/ 6 705 595 623 662 1300 12857/ L/ 5 616 594 712 662 1210 13748/ L/ 4 527 594 801 662 1121 14639/ L/ 3 438 594 890 662 1032 155210/ L/ 2 349 594 979 662 943 1641_______________________________________________________________________________________________________________________________________________

Example 4: floor-to-floor height = 2650 mm, T 1 = 260 mm, T 2 = 150 mm, rise = 204 mm, pitch = 60.7°,

projection = 4 mm, going = 224 mm

_______________________________________________________________________________________________________________________________________________



1/ L/ 11 1400 618 228 636 2018 8642/ L/ 10 1286 618 342 636 1904 9783/ L/ 9 1172 618 456 636 1790 10924/ L/ 8 1058 618 570 636 1676 12065/ L/ 7 944 618 684 636 1562 13206/ L/ 6 830 619 798 635 1449 1433

7/ L/ 5 716 619 912 635 1335 15478/ L/ 4 602 619 1026 635 1221 16619/ L/ 3 488 619 1140 635 1107 177510/ L/ 2 374 619 1254 635 993 1889_______________________________________________________________________________________________________________________________________________


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Quarter turn: 13 treads (cont)Example 5: floor-to-floor height = 2500 mm, T 1 = 260 mm, T 2 = 150 mm, rise = 192 mm, pitch = 55.6°,


_______________________________________________________________________________________________________________________________________________



1/ L/ 11 1570 642 262 620 2212 882

2/ L/ 10 1439 641 393 620 2080 10133/ L/ 9 1308 641 524 621 1949 11454/ L/ 8 1177 640 655 621 1817 12765/ L/ 7 1046 640 786 622 1686 14086/ L/ 6 915 639 917 622 1554 15397/ L/ 5 784 639 1048 622 1423 16708/ L/ 4 653 638 1179 623 1291 18029/ L/ 3 522 638 1310 624 1160 193410/ L/ 2 391 637 1441 624 1028 2065_______________________________________________________________________________________________________________________________________________

Quarter turn: 14 treadsExample 6: floor-to-floor height = 3000 mm, T 1 = 260 mm, T 2 = 150 mm, rise = 214, pitch = 66.9°,

projection = –19 mm, going = 182 mm

_______________________________________________________________________________________________________________________________________________

Stairs a L a b L b A B classification* (mm) (mm) (mm) (mm) (mm) (mm)_______________________________________________________________________________________________________________________________________________

1/ L/ 12 1261 600 182 659 1861 8412/ L/ 11 1170 599 273 660 1769 9333/ L/ 10 1079 599 364 660 1678 10244/ L/ 9 988 599 455 660 1587 11155/ L/ 8 897 598 546 661 1495 1207

6/ L/ 7 806 598 637 661 1404 12987/ L/ 6 715 598 728 661 1313 13898/ L/ 5 624 598 819 661 1222 14809/ L/ 4 533 597 910 662 1130 157210/ L/ 3 442 597 1001 662 1039 166311/ L/ 2 351 597 1092 662 948 1754


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Quarter turn: 14 treads (cont)Example 7: floor-to-floor height = 2850 mm, T 1 = 260 mm, T 2 = 150 mm, rise = 204 mm, pitch = 61.3°,


_______________________________________________________________________________________________________________________________________________



1/ L/ 12 1492 613 224 638 2105 862

2/ L/ 11 1380 614 336 637 1994 9733/ L/ 10 1268 614 448 637 1882 10854/ L/ 9 1156 614 560 637 1770 11975/ L/ 8 1044 615 672 637 1659 13096/ L/ 7 932 615 784 636 1547 14207/ L/ 6 820 615 896 636 1435 15328/ L/ 5 708 616 1008 636 1324 16449/ L/ 4 596 616 1120 635 1212 175510/ L/ 3 484 616 1232 635 1100 1867

11/ L/ 2 372 616 1344 635 988 1979_______________________________________________________________________________________________________________________________________________

Example 8: floor-to-floor height = 2700 mm, T 1 = 260 mm, T 2 = 150 mm, rise = 193 mm, pitch = 56.0°,


_______________________________________________________________________________________________________________________________________________

Stairs a L a b L b A B classification* (mm) (mm) (mm) (mm) (mm) (mm)_______________________________________________________________________________________________________________________________________________

1/ L/ 12 1690 635 260 620 2325 8802/ L/ 11 1560 635 390 620 2195 10103/ L/ 10 1430 635 520 620 2065 11404/ L/ 9 1300 635 650 620 1935 12705/ L/ 8 1170 635 780 620 1805 1400

6/ L/ 7 1040 635 910 620 1675 15307/ L/ 6 910 635 1040 620 1545 16608/ L/ 5 780 635 1170 620 1415 17909/ L/ 4 650 635 1300 620 1285 192010/ L/ 3 520 635 1430 620 1155 205011/ L/ 2 390 635 1560 620 1025 2180


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Half turn: 13 treadsExample 9: floor-to-floor height = 2650 mm, T 1 = 260 mm, T 2 = 150 mm, rise = 204 mm, pitch = 60.7°,


_______________________________________________________________________________________________________________________________________________



1/ L'/ 11 1400 618 228 640 2018 868

2/ L'/ 10 1286 618 342 640 1904 9823/ L'/ 9 1172 618 456 640 1790 10964/ L'/ 8 1058 618 570 640 1676 12105/ L'/ 7 944 618 684 640 1562 13246/ L'/ 6 830 619 798 640 1449 14387/ L'/ 5 716 619 912 640 1335 15528/ L'/ 4 602 619 1026 640 1221 16669/ L'/ 3 488 619 1140 640 1107 178010/ L'/ 2 374 619 1254 640 993 1894

_______________________________________________________________________________________________________________________________________________

* The first figure gives the number of treads on the lower straight flight. The letter L' indicates a 180° turnlanding. The last figure gives the number of treads on the upper straight flight.

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APPENDIX HGERMAN AND USA RECOMMENDATIONS

German recommendationsA German Code of Practice, ZH 1/ 26210, under Accident Prevention Regulations, exists for stairs withalternating treads. The Code states that this type of stairs is an emergency solution which should be used onlywhen the space problem allows no other solution. Suggested suitable uses are for cellar manhole stairs or forservice stairs in boiler houses and machine rooms.

For straight flights, step widths of 450 mm to 500 mm are said to be suitable. If the space available is wider, thegap between wall and stairs edge must be sealed. This type of stairway does not allow users to pass one another.

The Code indicates that this type of stairs can be built in wood, steel, stone or concrete.

The type of tread design recommended in the Code is shown in Figure H1. The following notation is used forthis example:

N is the number of treads (in this report the shaped upper platform is not counted as a tread)

D (for a single straight flight) is the horizontal distance from top landing (back edge of top tread) to frontedge of bottom nosing (in mm)h is the floor-to-floor height (in mm)G c is the going along the centre line of the width as shown in Figure H 1

G w is the going along the line w—w as shown in Figure H 1

W is the width between the strings (in mm)

w

cw

D

GC

Gw

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r = h (37) ----------------------

N + 1

D = (N + 1.5)G c (38)

The optimum number of treads N is given by:

N = 2h + D + 170 – 1 (39) -----------------------------------------------

630

If the result is not an integer, it is rounded down from up to 0.5 or up for over 0.5.

At the line w—w, G w = 2G c (40)

Thus across the stairs width, going varies from G c at the centre of the width to G w at line w—w and is then

constant (G w) with the exception of the top tread.

The pitch is given by:

tan θ = r (41) ------------

G c

or tan θ = 2r (42) ------------

G w

The angle of taper of the tread is given by:

tan β = G c (43) ------------

W

The Code recommends that:

D ~ 0.5h (44)

and rise is between 220 mm and 250 mm.

The Code gives an example with the following characteristics:

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In order to get an indication of the dimensional limits set by the Code, take an 11 tread stairs with a 250 mmrise. This would give:

h = 3000 mmN = 11r = 250 mm

Using equations (38), and (40) to (42):

G c = 111.2 mm

G w

= 222.4 mm

θ = 66.0°

Hence in this example D is 0.46h .

The above example indicates limits of maximum rise of 250 mm, minimum going on line w—w of 222 mm, and amaximum pitch of 66°.

USA recommendations

In the USA, these stairs were referred to for the first time in the National Fire Protection Association NFPA 101Life Safety Code 19889. The Code says that alternating tread devices may only be used for access to unoccupiedroof spaces or as a secondary means of escape from storage elevators; also towers and elevated platforms aroundmachinery and boiler rooms subject to occupancy only by not more than three able-bodied adults. Thealternating tread stairs design differs in having three strings, one along the centre of the stairs width whichseparates the user's feet and the other two at the sides. Each tread is only 'half-width'.

The requirements are:

(i) The occupant load served shall not be more than three(ii ) The rise shall not exceed 203 mm(ii i) Treads shall have a minimum projected tread depth (equivalent to going in this report) of 229 mm with

each tread providing 267 mm of depth including overlap(iv) The initial t read of the stairs shall begin at the same elevation as the platform, landing or floor surface(v) The alternating treads shall not be laterally separated by more than 50 mm(vi) Handrails shall be provided on both sides of the stairs(vii) The clear width between handrails shall be a minimum of 432 mm and shall not exceed 610 mm(vi ii ) A minimum distance of 152 mm shall be provided between the stairs handrail and any other object(ix) Headroom shall not be less than 2030 mm

Requirement (iv) relates to the central string. Requirement (vii) is to allow easier carrying of small objectsoutside the handrail.

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TABLES

Table 1Where the loft stairs led to

Room Site survey(number)

Post & tel survey(number)

Total(number) (%)

Extra bedroomOfficeGuest/ spare roomBath/ shower room

PlayroomSitting roomHobby roomStore roomOther

6819155

43200

312

132

00013

99 5921 1328 177 4

4 23 22 11 13 2

Total 116 52 168 100

Table 2 Type of dwelling

Type of dwelling Site survey(number)


Total(number) (%)

BungalowHouse

1485

1834

32 21119 79

Total 99 52 151 100

Table 3Users of loft stairs

Age range of users(yrs)

Site survey(number)


Total(number) (%)

0–45–910–14

15–2930–4445–6465–7475+Not known

133747

469955520

102936

32641820

22

23 466 1383 16

78 15163 3273 147 12 –

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Table 5 Time since installation of loft stairs

Time periodmonths

Site survey(number)


Total(number) (%)

0–45–910–1415–1920–2425–29

30–36

11163325112

1

64

137

117

4

17 1120 1346 3032 2122 159 6

5 3Total 99 52 151 100

Table 6Frequency of use of main and loft stairs (site sample only)

Number of times usedper day

Main stairs(number) (%)

Loft stairs(number) (%)

<11–67–1213–1819+

0 05 6

23 2731 3626 31

6 658 5923 237 75 5

Total 85 100 99 100

Table 7Design of stairs

Stairs design Main stairs

(number) (%)

Loft stairsSite Post & tel Total

(number) (number) (number) (%)

Straight 22 26 62 39 101 671/ 4 or 1/ 2 turn 39 46 33 12 45 30Winder 24 28 3 0 3 2

Spiral 0 0 1 0 1 1Not known 0 0 0 1 1 1

Total 85 100 99 52 151 100

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Table 8Number of risers

Risers

(number)

Main stairs

(number) (%)



10 0 0 1 0 1 111 2 2 0 3 3 212 3 4 8 9 17 1113 13 15 46 23 69 4614 39 46 37 14 51 34

15 21 25 4 0 4 316 3 4 3 0 3 217 3 4 0 0 0 018 1 1 0 1 1 1Not known 0 0 0 2 2 1

Total 85 100 99 52 151 100

Table 9

Open or closed risers

Risers

(number)

Main stairs

(number) (%)



Open 4 5 57 16 73 59Closed 81 95 42 9 51 41

Total 85 100 99 25 124 100

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Table 10Alternating tread stairs survey: dimensions of straight flight section __________________________________________________________________________________________________________________________________________________

Case Depth Depth Projection Distance Going Rise Pitch Pitchno. long short calc. meas.

(T 1) (T 2) (P ) (K ) (G ) (r ) (θ) (θ)

(mm) (mm) (mm) (mm) (mm) (mm) (°) (°) __________________________________________________________________________________________________________________________________________________

96 270 150 10 130 250 195 56.3 5620* 267 157 47 157 267 220 54.5 5534 266 159 13 120 227 207 59.9 6026 265 164 20 121 222 191 57.6 5789 265 155 0 110 220 200 61.2 6129* 265 155 0 110 220 205 61.8 627 265 153 0 112 224 193 59.9 6111* 265 153 10 122 234 195 58.0 5831* 265 153 8 120 232 205 59.7 5925 265 152 18 134 250 202 56.4 5491 265 150 –5 110 220 210 62.4 6490 265 150 –2 113 226 215 62.3 63

21 264 153 0 111 222 202 61.2 6433* 263 155 8 116 224 200 59.9 6128 263 153 –3 107 214 204 62.3 6530* 263 153 –5 105 210 209 63.3 6488 262 155 –7 100 200 210 64.5 679 262 152 16 126 236 194 57.0 594 262 150 18 130 242 190 55.6 5664 262 150 –15 97 194 210 65.2 6669 261 150 4 115 226 202 60.3 6141 260 160 10 110 210 205 61.8 6212 260 155 3 108 213 200 61.6 6286 260 155 10 115 220 200 60.1 5822* 260 155 0 105 210 210 63.4 6283 260 152 0 108 216 210 62.8 6279 260 150 20 130 240 185 54.9 5443 260 150 20 130 240 190 55.6 5551 260 150 15 125 235 190 56.7 5597* 260 150 15 125 235 190 56.7 5914* 260 150 30 140 250 195 54.3 55

66* 260 150 10 120 230 195 58.4 6032 260 150 10 120 230 200 59.0 6035 260 150 2 112 222 200 60.8 6044* 260 150 10 120 230 200 59.0 6045 260 150 10 120 230 200 59.0 6060 260 150 10 120 230 200 59.0 6063 260 150 0 110 220 200 612 59p

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Table 10Alternating tread stairs survey: dimensions of straight flight section (cont) __________________________________________________________________________________________________________________________________________________

Case Depth Depth Projection Distance Going Rise Pitch Pitchno. long short calc. meas.

(T 1) (T 2) (P ) (K ) (G ) (r ) (θ) (θ)

(mm) (mm) (mm) (mm) (mm) (mm) (°) (°) __________________________________________________________________________________________________________________________________________________

61* 260 150 10 120 230 210 60.3 6299 260 150 –10 100 200 210 64.5 6498* 260 150 40 150 260 235 57.4 6024 258 150 15 123 231 220 60.8 6277* 250 150 0 100 200 195 62.9 6078 250 150 10 110 210 200 61.2 5859 250 150 10 110 210 205 61.8 6267 250 150 10 110 210 205 61.8 6081* 250 140 10 120 230 190 57.7 5592* 250 150 Spiral 22518 241 121 0 120 240 194 58.3 5810 240 130 8 118 228 195 58.8 59

36 240 125 0 115 230 198 59.9 5813 240 125 –10 105 210 210 63.4 643 240 120 0 120 240 195 58.4 5617* 240 120 –3 117 234 200 59.7 611 240 120 0 120 240 205 59.7 60100 240 120 10 130 250 gap 205 57.6 578 240 120 –27 93 186 214 66.5 6872 240 118 0 122 244 gap 215 60.4 5982 240 118 –2 120 240 215 60.8 5970 240 117 6 129 252 gap 195 56.5 562 240 117 –5 118 236 200 59.5 6075* 240 117 –5 118 236 215 61.2 6062 240 115 0 125 250 gap 200 58.0 5865 240 115 –20 105 210 205 62.9 6087 240 115 –18 107 214 220 64.1 6376* 236 115 –48 73 146 222 71.8 7247 235 120 –20 95 190 200 64.6 605 235 120 0 115 230 209 61.2 6115* 235 118 0 117 234 205 60.3 62

54* 235 118 –37 80 160 215 69.6 6355 235 115 –5 115 230 210 61.3 6123 234 115 –2 117 234 203 60.0 6074* 230 116 0 114 228 210 61.5 6027 230 115 0 115 230 200 60.1 6053 230 115 –10 105 210 210 63.4 6437 230 110 20 100 200 210 645 62p

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Table 11Dimensions of main stairs _____________________________________________________________________________________________________________________________________

Case Number Overlap Going Rise Pitch Pitchno. of risers calc. meas.

(mm) (mm) (mm) (°) (°) _____________________________________________________________________________________________________________________________________

1 17 35 185 185 45 462 14 35 205 193 43 433 15 28 228 185 39 40

4* 15 35 235 190 39 395 15 16 210 178 40 426* 16 35 205 175 41 407 14 35 210 197 43 448 14 40 190 200 47 489 14 25 205 182 42 4410 11 25 230 190 40 4113 12 35 195 187 44 4414 13 35 210 190 42 43

16 15 25 224 175 38 3818 18 25 190 160 40 4019 14 45 210 195 43 4020 13 35 205 203 45 4621 15 50 205 182 42 4022 14 30 240 190 38 3823 15 30 190 185 44 4424 15 30 190 200 47 4725 14 25 225 197 41 45

26* 14 20 232 199 41 4327 15 30 190 190 45 4328 14 30 200 190 44 4529* 17 35 222 187 40 4030* 13 32 195 200 46 4831 14 35 215 185 41 4032 14 30 198 195 45 4533 13 30 213 195 43 43

34 14 40 200 200 45 4335* 11 20 210 220 46 4936 14 35 210 210 45 4437 14 20 185 190 46 4438 13 0 230 200 41 4240 14 0 230 170 37 40

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Table 11Dimensions of main stairs (cont) _____________________________________________________________________________________________________________________________________

Case Number Overlap Going Rise Pitch Pitchno. of risers calc. meas.

(mm) (mm) (mm) (°) (°) _____________________________________________________________________________________________________________________________________

54* 15 23 230 170 37 3756 13 0 200 190 44 4557 14 20 240 180 37 40

58 14 0 200 190 44 4559 14 20 220 200 42 4460 13 0 250 190 37 4061 13 20 220 220 45 4863 14 0 220 190 41 4464 14 40 200 200 45 4665 14 20 220 180 39 3966 14 20 220 180 39 4467 14 20 180 200 48 42

68 15 0 220 200 42 4569* 15 10 200 200 45 4270 17 40 260 190 36 3671* 15 30 200 200 45 4572 15 15 210 190 42 4273 13 25 205 205 45 4574* 15 35 205 175 41 4475 15 30 195 170 41 4076 14 20 220 190 41 40

77 14 0 230 200 41 4478 13 0 230 200 41 4280 14 0 200 180 42 4681 15 0 260 190 36 4082 14 15 215 185 41 4083 16 35 186 180 44 4484* 14 15 230 180 38 3886 14 25 220 190 41 40

87 15 25 205 220 47 4688* 14 25 200 165 40 4090 15 25 180 187 46 4492 14 0 230 180 38 3894 16 0 200 170 40 4295 13 0 230 210 42 40

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Table 12Depth of tread on loft stairs: longer side (site sample only)

Depth of tread (mm) Number %

270–279 1 1260–269 51 52250–259 7 7240–249 17 17230–239 12 12220–229 10 10210–219 1 1

Total 99 100

Table 13Depth of tread on loft stairs: shorter side (site sample only)

Depth of tread (mm) Number %

160–169 2 2150–159 56 57

140–149 1 1130–139 1 1120–129 11 11110–119 28 28

Total 99 100

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Table 14Measured pitch of stairs (site sample only)

Pitch(°)



72 0 0 1 171 0 0 0 070 0 0 0 069 0 0 0 068 0 0 1 167 0 0 1 1

66 0 0 1 165 0 0 1 164 0 0 7 763 0 0 3 362 0 0 18 1861 0 0 12 1260 0 0 25 2659 0 0 7 758 0 0 7 7

57 0 0 2 256 0 0 4 455 0 0 6 654 0 0 2 253 0 0 0 052 0 0 0 051 0 0 0 050 0 0 0 049 1 1 0 048 3 4 0 047 1 1 0 046 6 7 0 045 10 12 0 044 16 19 0 043 6 7 0 042 11 13 0 041 2 2 0 0

40 19 22 0 039 3 4 0 038 4 5 0 037 2 2 0 036 1 1 0 0

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Table 15Going of stairs (site sample only)

Going(mm)



260–269 3 4 2 2250–259 3 4 6 6240–249 2 2 9 9230–239 16 19 28 29220–229 14 16 25 26210–219 12 14 14 14

200–209 21 25 8 8190–199 9 11 3 3180–189 5 6 1 1170–179 0 0 0 0160–169 0 0 1 1150–159 0 0 0 0140–149 0 0 1 1

Total 85 100 98 100

Table 16Rise of stairs (site sample only)

Rise(mm)



231–235 0 0 1 1226–230 0 0 1 1221–225 0 0 2 2216–220 3 4 3 3211–215 0 0 10 10206–210 5 6 19 19201–205 2 2 24 24196–200 17 20 21 21191–195 4 5 12 12186–190 22 26 5 5181–185 7 8 1 1

176–180 14 16 0 0171–175 3 4 0 0166–170 6 7 0 0161–165 1 1 0 0156–160 1 1 0 0




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Table 17Projection on loft stairs (site sample only)

Projection (mm) Number %

45 to 54.9 1 135 to 44.9 1 125 to 34.9 1 115 to 24.9 10 105 to 14.9 27 280.1 to 4.9 5 50 27 28

–0.1 to –4.9 5 5–5 to –14.9 13 13–15 to –24.9 5 5–25 to –34.9 1 1–35 to –44.9 1 1–45 to –54.9 1 1

Total 98 100

Table 18Dimensional characteristics of survey stairs Designs A, B and C

Characteristic Design A Design B Design C

Depth-long (mm) 215 to 270 225 to 265 220 to 265Depth-short (mm) 115 to 164 110 to 155 110 to 155Projection (mm) 2 to 47 0 –2 to –48Going (mm) 191 to 267 200 to 250 146 to 240Rise (mm) 185 to 235 193 to 230 197 to 222Calculated pitch (°) 54.3 to 64.1 58.0 to 63.4 59.5 to 71.8Sizes of gaps (mm) 10, 12 4, 5, 10, 10

Table 19 Tread covering

Tread covering Main stairs

(number) (%)



Wood 3 4 95 47 142 94Carpet 82 96 4 3 7 5Other 0 0 0 1 1 1Not known 0 0 0 1 1 1

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Table 20 Tread width of loft stairs (site sample only)

Width of tread (mm) Number %

850–889 1 1810–849 3 3770–809 0 0730–769 3 3690–729 37 37650–689 8 8610–649 18 18

570–609 25 25530–569 4 4

Total 99 100

Table 21Handrail provision on stairs

Handrail Main stairs

(number) (%)

Loft stairs

Site Post & tel Total(number) (number) (number) (%)

Left or right 74 87 35 14 49 32Both sides 8 9 62 36 98 65Neither side 3 4 2 2 4 3

Total 85 100 99 52 151 100

Table 22Width between rails (site sample only)

Clear width(mm)



850–899 9 11 1 1800–849 18 21 1 1750–799 33 39 5 5700–749 12 14 12 12

650–699 3 4 14 14600–649 1 1 41 41550–599 1 1 17 17500–549 0 0 6 6Not known/ no rail 8 9 2 2




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Table 23Handrail height

Height(mm)



1200–1249 0 0 1 11150–1199 0 0 1 11100–1149 0 0 6 41050–1099 1 1 5 31000–1049 2 2 11 7950–999 1 1 26 16

900–949 3 3 29 18850–899 17 19 27 17800–849 19 21 28 18750–799 28 31 7 4700–749 8 9 5 3650–699 2 2 3 2600–649 2 2 8 5550–599 0 0 1 1500–549 0 0 1 1

450–499 1 1 0 0Not known 6 7 0 0

Total 90 100 159 100

Table 24Handrail extension (site sample only)

Handrail extension Main stairs

(number) (%)

Loft stairs

(number) (%)Extends beyond top and bottomsteps 10 11 60 38Extends beyond top step but endsbefore bottom 28 31 53 33Ends before bottom and top steps 47 52 26 16Extends beyond bottom step butends before top 2 2 14 9

Not known/ no handrail 3 3 6 4Total 90 100 159 100

Table 25Handrail shape (site sample only)

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Table 26Dimensions of handrail (site sample only)

Handrail shape Main stairsDiameter Horizontal Vertical

range range range(mm) (mm) (mm)

Loft stairsDiameter Horizontal Vertical

range range range(mm) (mm) (mm)

Round 30–49 20–69Oval 55–90 30–50Horizontal 60–110 30–55 70–140 20–40Vertical 27–30 50–165 17–44 60–135

Table 27Clearance between handrail and wall

Clearance of handrail(mm)



90–99 0 0 1 180–89 1 5 0 0

70–79 1 5 0 060–69 2 10 5 650–59 7 35 30 3840–49 2 10 28 3630–39 4 20 6 820–29 3 15 4 510–19 0 0 4 5

Total 20 100 78 100

Table 28Infill between handrail and stairs

Infill Main stairs

(number) (%)



Vertical rails 9 35 5 9 14 10Sloping plank 17 21 42 17 59 40Solid 31 38 45 19 64 44Other 5 6 5 5 10 7

Total 82 100 97 50 147 100

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Table 30Clear headroom of loft stairs

Clear headroom (mm) Number %

2900+ 9 92800–2899 1 12700–2799 0 02600–2699 2 22500–2599 0 02400–2499 3 32300–2399 1 1

2200–2299 2 22100–2199 7 72000–2099 16 161900–1999 3 31800–1899 10 101700–1799 12 121600–1699 7 71500–1599 3 31400–1499 2 2

Not known 21 21Total 99 100

Table 31Steepness of stairs

Response Main stairs

(number) (%)


(number) (number) (number) (%)Steep 1 1 82 41 123 81Just right 83 98 17 9 26 17Shallow 1 1 0 0 0 0No response 0 0 0 2 2 1

Total 85 100 99 52 151 100

Table 32Ease of use of loft stairs compared to main stairs (site sample only)

Response Going up(number) (%)

Going down(number) (%)

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Table 34Section of main and loft stairs presenting the most difficulty

Section Main stairs

(number) (%)



UP:Top 14 16 18 3 21 14Middle 4 5 6 2 8 5Bottom 0 0 14 3 17 11None 67 79 61 44 105 70

Total UP 85 100 99 52 151 100DOWN:Top 12 14 26 12 38 25Middle 4 5 7 0 7 5Bottom 1 1 11 2 13 9None 68 80 55 38 93 62

Total DOWN 85 100 99 52 151 100

Table 35 Turning round on the stairs


(number) (%)



UP:Difficulty 2 2 52 32 84 56No difficulty 72 85 25 13 38 25Would not do it 11 13 22 6 28 19No response 0 0 0 1 1 1

Total UP 85 100 99 52 151 100

DOWN:Difficulty 3 4 47 36 83 55No difficulty 70 82 27 10 37 25Would not do it 12 14 25 5 30 20No response 0 0 0 1 1 1

Total DOWN 85 100 99 52 151 100

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Table 36Speed of use of loft stairs compared with main stairs

Speed Site survey(number)

Post & tel survey*(number)

Total(number) (%)

UP:Slower 71 31 102 74Same 12 13 25 18Faster 2 2 4 3No response 0 6 6 4

Total UP 85 52 137 100

DOWN:Slower 41 34 75 55Same 44 12 56 41Faster 0 0 0 0No response 0 6 6 4

Total DOWN 85 52 137 100

* some respondents gave a response despite 18 living in bungalow and therefore had no main stairs installed forcomparison.

Table 37Hurrying on loft stairs


(number) (%)



Difficulty hurrying 3 4 27 25* 52 34No difficulty 82 96 72 27# 99 66

Total 85 100 99 52 151 100

Additional information:* 9 respondents were not able to go up and down quickly.# 27 respondents stated they could easily go up and down quickly.

Table 38Handrail use


(number) (%)


(number) (number) (number) (%)p o w ell - willi a m s@ ak s w a rd .


09/08/2012 , U n


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Table 39Rating of handrail height

Rating Main stairs(number) (%)


Too high 0 0 16 10About right 86 96 131 82Too low 0 0 7 4Not known 4 4 5 3

Total 90 100 159 100

Table 40Rating of handrail height on loft stairs by children and adults (postal and telephone surveys only)

Rating Children(number) (%)

Adults(number) (%)

Too high 16 31 2 4About right 28 54 47 90Too low 0 0 1 2

Not known 8 15 2 4Total 52 100 52 100

Table 41Rating of safety of loft stairs compared to main stairs

Response Site survey(number)

Post & tel survey*(number)

Total(number) (%)

Loft stairs less safe than main stairs 73 25 98 77Main and loft stairs equally safe 9 17 26 20Loft stairs safer 3 0 3 2

Total 85 42 127 100

* 4 respondents gave a rating despite living in bungalows and not therefore having a main stairs for comparison.

p o w ell - willi a m s@ ak s w a rd .

c o m , A K S W a rd , 09/08/2012 , U n


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FIGURES

T2

T1

P

P

Pitchline

Pitchlines

Figure 1

Alternating tread stairs


c o m , A K S W a rd , 09/08/2012 , U n

c o n t r oll ed C o p y .

1

41 1



r

G

K

P+ve4

3

2

1

θ

r

G

K

P=0

θ

r

G

K

P–ve

θ

T2 T2

T2

T1

G

G

4

G

2

(a) Design A (a) Design B (a) Design C

T2 T2

T1

G

T1

G3

1

P+ve

P=0P

– ve

G Q

GG

T2

Figure 2Design of straight flight stairs


c o m , A K S W a rd , 09/08/2012 , U n




D

Pitchline

h

d

Line of minimumclear headroom (2 m)

above pitchline

P

T2

T1

r

H

θθ


c o m , A K S W a rd , 09/08/2012 , U n




Figure 4 Alternating tread stairs with central supporting beam and two handrails



Figure 5 Alternating tread stairs with central supporting beam and one handrail



Figure 6 Alternating tread stairs with quarter-turn landing



Figure 7 Alternating tread stair with side strings, open risers and quarter-turn landing



Figure 8 Alternating tread stairs with side strings and downstand at risers



Figure 9 Alternating tread stairs with closed risers (closed by sloping backing board) and carpet on treads



Figure 10 Alternating tread stairs with objects on the treads and landing



Figure 11 Alternating tread stairs with objects stored or left around

Documents

BRE Alternating Tread Stair Design