Inter-connected floorsThe Dutch TNO (Netherlands Organisation for appliedscientific research), has conducted research into theshear connections between a LEWIS® concrete floorand the underlying supporting timber joists whenthey are joined by means of screwnails. The application procedure for inter-connected floorsis as follows: In order to prevent initial deflexionresulting from the extra weight of the concretemortar, the timber joists are temporarily underpinned.After the LEWIS® sheets have been placed at rightangles on to the joists with sufficient overlap (see theseparate application instructions) they are fastenedby a flat head hardened screwnail, type no. 11 dia > 3.4 mm (3.65 mm) length 63.5 mm (2.5”), placed ineach lower flute. Next the’ fine grade’ concretemortar is poured in a 30 mm-35 mm layer, measuredfrom the upper flutes of the LEWIS® sheeting.When the concrete has set (after approximately 7 days), the struts can be removed, the floorcompleted and lightweight partition walls erected.The values of strength and rigidity of suchinterconnected floors have been obtained frompractical testing and have further been arithmeticallydetermined and quantified.

STRUCTURAL DESIGN AND CALCULATIONS

Non inter-connected floorsA. Timber joistsMaximum clear span in m1 for timber joists of strength class SC3. The maximum clear span depending on therequired allowable load and joist sizes can be read off from the table below.

Table Imposed load not exceeding 1.5 kN/m2* (dead load more than 0.50 but not more than 1.25 kN/m2).

** joist sizes spacing of joists clear spanin mm 400 450 600

63 x 150 3.10 2.98 2.63 m1

63 x 175 3.61 3.47 3.03 m1

75 x 200 4.35 4.19 3.74 m1

* Dead load is the load supported by the joist excluding the mass of the joist itself.** According to BS 4471: Part 1: 1987. Timber of strength class SC3 as defined in BS 5268:part 2 : 1984.

B. Calculation ExampleIt has been decided to place a LEWIS® floor in adomestic house on existing timber joist, class SC3.An inter-connected structural design floor is notrequired. The joist sizes are 63 mm x 175 mm, theclear span 3.03 m and the spacing of joists 600 mm(see table).

Load bearing capacity of timber joists≤ 2.75 kN/m2

Weights of structural elements:kN/m2

joists 0.000t+g timber boards -- )LEWIS® sheets 0.058‘fine grade’ concreteaverage 28 mm** 0.560partition walls -- )***

Total 0.618 imposed loaddwelling units 1.500

Total 2.118 (<2.75 kN/m2)

Conclusion: more than adequate.

*) the calculation is based on the existing t+g timber boards being removed.

**) mimimum concrete cover of 20 mm + half theprofile height.

***) lightweight partition walls have not been included in calculation.

C. Strength analysis for the supporting joistconstruction according to British StandardsThe strength and rigidity of the timber or steelfloor framing concerned should always be checked.In the case of simple loads directly supported bythe underlying structure the table on this pagemay be consulted as well as the tables in ApprovedDocument A (Structure) of the Building Regulations1985. For non-standard structures please refer tothe calculation procedures according to the standards and regulations currently in force.

Design tables ‘joist sizes’ inter-connectedconstructions (for other spacing of joists see TNOreport B88.078). In the calculation, in addition to thedead load of the timber joists, the following deadloads are assumed:-LEWIS® floor 0.90 kN/m2

-ceiling finish 0.25 kN/m2

N.B. When lightweight partition walls are put up theimposed load should be increased by ≥1.0 kN/m2

according to BS 6399: Part 1.1984

Permissible theoretical span Lt in the case of timber joisting centre-to-centre 600 mm

cross uniformly divided floor loadsection 2kN/m2 2.5kN/m2 4 kN/m2

in mm

63x160 2988 mm 2916 mm 2404 mm

63x175 3359 mm 3177 mm 2625 mm

63x200 3860 mm 3604 mm 2976 mm

75x175 3572 mm 3343 mm 2831 mm

75x200 4064 mm 3810 mm 3222 mm

75x225 4545 mm 4263 mm 3611 mm

95x150 3214 mm 3087 mm 2676 mm

100x150 3286 mm 3142 mm 2716 mm

100x200 4407 mm 4137 mm 3598 mm

120x230 5313 mm 4999 mm 4362 mm

FIRE RESISTANT FLOORSThe fire resistance of structural flooring depends greatly on the stability and the load bearing capacity of the timber joists. On the basis of the fire test procedures carried out by the Dutch testing institute TNO and calculations by the Technical University of Braunschweig,Germany, the fire resistance ratings of various LEWIS® floorconstructions have been determined. To prevent the spread of fire, the ”fine grade” concrete

mortar should becarefully worked along the floor/wall joints. Penetrations are sealed off with special purpose materials.

SPECIAL CONSTRUCTIONSRaised floors on various supporting structures

The latter could comprise pre-cast concrete beams, aeratedconcrete, timber joists or brickwork (See sketch 8). The sheets should be fixed on aerated concrete with drillpointscrews, on masonry and concrete beams with mortar and ontimber joists with nails or screwnails.

Slanting, uneven floor constructionsLevel differences in existing timber floor constructions can becancelled out by using wedge shaped wooden laths. The final smooth finish can then be achieved by applying a layer of ‘fine grade’ concrete. (See sketch 7).

Sloping floorsSlopes in existing floors, found in former cinemas and theatrescan be dealt with by using timber joists and/or aerated concrete.

Mezzanine floors on steel beamsThe LEWIS® sheets are fixed onto the underlying (steel) loadbearing structure with rivets. Studwelding is another manner or fixing. (See sketch 9).

Converting roof-floors to inner floorsLEWIS® sheets provide an excellent solution when adding a storeyto a building where the existing roof-floor is converted into anupper-storey floor. After removing the roof panelling, which often consists ofinsulated sheets or t+g timber boards the LEWIS® sheets aresimply placed directly onto the timber framing and the floor isfinished with ‘fine grade’ concrete.

Sketch 9

P.O.Box 102 • 3300 AC Dordrecht • The Netherlands • Tel.no. 00-31-78-617 44 00 • Fax 00-31-78-6171006Pieter Zeemanweg 107 • Industrial Est. Dordrecht West • E-mail: reppel@reppel.nl • Website: www.reppel.nl

REP

010

5GB

Results in minutes according to research by the Dutch TNO

Sketch 8

Dead loadsDead loads are calculated from the unitweights given in BS 648 (Schedule of weightsof building materials) or from the actualknown weights of the materials used.

Fire test on a compositeLEWIS® floor structure.

structure structureFire resistance with without

ceiling ceiling

integrityflame resistance 60-90 60-94thermal insulation (180C0)

The fire resistance in minutes is mainly due to the cross-sections of the timber joists, the spacing of the joists and the imposed floor load under fire conditions.

LEWIS® concrete floor on timber joists with specially adapted,completely flame and smoke resistant edging connection.Fire resistance rating: F60-94 minutes.

Testing the load bearing capacity

Sketch 7

Method of fixture/ temporary underpinning

Sketch 6

≤ 2500 mm

4. Minimum concrete thicknesses

standard floorin domestic housing: 16 + 20 = 36 mmstandard floorin institutional buildings: 16 + 30 = 36 mmsound resistant floor: 16 + 34 = 50 mminter-connected floor: 16 + 30 = 46 mmunderfloor heating: 16 + *20 + 20 = 56 mm

N.B. profile height LEWIS® sheet 16 mm +concrete layer=total thickness of floor.

* assumed diameter of underfloor heating piping.

Imposed floor loads

The minimum imposed floor loads andconcentrated loads for buildings are accordingto BS 6399 : Part 1:1996.

D. Miscellaneous informationLoad bearing capacity of completed LEWIS®

concrete floorThe following tables are intended to give theproperties resulting from the combined use of theLEWIS® dovetailed profile and ‘fine grade’ concrete.

1 Uniformity distributed load

* floor thickness clear span load bearing(ht) in mm in mm (Lt) capacity kN/m2

50 600 30.250 900 19.550 1200 13.850 1500 9.775 2000 6.175 2500 4.1

2. Concentrated load

* floor thickness clear span kN(ht) in mm in mm (Lt) 100x100 mm

50 600-1,000 750 600-1,500 375 2,000-2,500 3*75 2,000-2,500 7*

* extra reinforcement size 5 x 150 mm is required.For higher concentrated loads please refer toTNO report 99 CON-BIS-R 5006/2.

3. Load bearing capacity of LEWIS® sheets duringapplication without concrete.

clear span load bearing safety(Lt)in mm capacity kN/m2 *(zul-p) factor

600 8.5 1.7900 5.7 1.7

**1200 3.8 1.7**1500 2.5 1.7

* values according to DIN 18807, part 3.Load bearing capacity for statically indeterminatestructures including a maximum deflexion of <1/150.

** underpin temporarily until the concrete has set.

A calculation model and a computer programme havebeen developed in order to be able to calculate everyconceivable construction. In the calculation modeland design tables wide safety margins areincorporated.

25 25,525 39

16

35 3529

The productLEWIS® sheets are rolled selfsupporting,dovetailed, steel reinforcement sheets which are used for shuttering and reinforcing lightweight concrete floors of limited thickness on (for the most part) timber floor framing.

Special properties

* Long-term durability owing to use of qualifiedsteel.

* Simple to use because of special rolled profile.

* Can be laid directly on the floor joists.The t+g timber boards may be omitted resultingin savings on floor height and weight.

* Fire resistance ratings of 60 and 90 minutes wellwithin range.

* Airborne and impact sound transmission valuesof Dnt,w 56 dB L’nt,w 43 dB according toapproved document E of The BuildingRegulations 1985 achieved without difficulty.

* Increased strength and rigidity of floor framingresults in an extra load-bearing capacity of 30%for the floor as a whole.

* Water resistant structural flooring.

* Profile allows air circulation essential for timberpreservation.

* Total floor thickness limited to between 36 mmand 50 mm.

* High load bearing capacity combined with lowdead load of 0.6 - 0.9 kN/m2.

* Dead load and structural height reduced evenfurther on removal of t+g timber boards.

Method of installationIn our separate leaflet concerning the recommended method of installation, detailed instructions are given regarding laying the sheets, joints, length/width adjustment and voids, method of fixture and the compositionand pouring of the concrete. Our technical staff are always willing to answer your questions and give expertadvice on any of the various fields of application and appropriate LEWIS® floor systems.

WATER RESISTANT FLOORSIn renovation and restoration projectswhere the existing t+g timber boardsand/or joists are to be retained, water resistant floors using LEWIS® sheeting are inthe Netherlands traditionally the mostappropriate solution for the so-called ‘wetareas’ such as the bathroom, toilet, kitchen,utility room and changing room.In other words, in any area associated withdamp activities.

The water resistant junction of the floor withthe existing vertical masonry wall is achievedeither by strips of polyester-fibre basedroofing felt being fixed to the wall and workedinto the still-wet concrete or by applying special adhesive water resistant flashing ontothe completed concrete floor.‘Fine grade’concrete - sloped to drain - is worked onto the LEWIS® sheets. When set, ceramic tiles may be fixed. In the case of tiledfloors we advise the use of a silicone sealant forthe floor-wall joint and water repellent resin-based grouting for the remaining jointing.The earthing should conform to the regulationslaid down by the Local Electricity Board.

CERAMIC TILES, TERRAZZO, FLAT NATURAL STONE ON TIMBERThe use of LEWIS® sheeting guarantees a durable, stableconcrete underfloor. Ceramic tiles and flat natural stoneare usually fixed onto the floor using a tile adhesive. Please refer to the standards and regulations currently inforce for terrazzo finishes.

Detail a.: flat natural stonefinish and underfloor heating

Detail b.: terrazzo finish

Sketch 3Structural detail showing underfloorheating and thermal insulationbetween the joists.

Sketch 2Bathroom floor with pouredconcrete rim and water resistantedgings joined to new and existing masonry walls

Detail cWater resistant edging joined toexisting brickwork wall

Detail dWater resistant edging with poured concrete rim and aeratedconcrete compartment wall

Detail eWater resistant edging with pouredconcrete rim and composite plasterboard compartment wall

Sketch 5Composite timber floor structure omittingt+g timber boards with decorative ceiling,fibreglass in cavity and LEWIS® concretefloor on strips of Rockwool

Temporary fixture usingwedge-shaped wooden plugs.

COMPARTMENT FLOORS SEPARATINGDWELLINGSExisting buildings often still have sound andtherefore usable timber floors. In the case oflarge-scale maintenance, renovation or when abuilding’s function is altered, requirements instructural design have to be upgraded.This would be the case when, for instance,floors acquire the function of separating flatsin residential buildings.The LEWIS® floating floor construction complieswith the requirements for fire resistance, combustibility, airborne and impact sound transmission.Detailed test reports issued by internationallyrecognized testing institutes are available forreference.

Sketch 4Composite timber floor structure(joists and t+g timber boards) withplasterboard ceiling and LEWIS®

concrete floor on strips of Rockwool

Properties Dnt,w 56 dBL’nt,w 49 dBF ≥ 60 minutes

Technical detailsnominal width 630 mmeffective width 610 mmstandard lengths 1,220 mm

1,530 mm1,830 mm2,000 mm

length range 800-7,000 mm

dimentional tolerances: length 1-4 mmwidth 1-3 mm

moment of inertia lx = 3.6 cm4/m1

moment of resistance Wx = 3.0 cm3/m1

steel gauge 0.5 mmheight of profile 16 mmflange width 39/35 mmweight 0.058 kN/m2

minimum ‘fine grade’ concrete thickness: 16 mm profile height plus 20-34 mm depending on area of application.For composition and quality of concrete see separate application instructions.

Steel quality: S320GD + Z275 N-A-C according to NEN-EN10147

Properties: Dnt,w 50 dBL’nt,w 58 dBF ≥ 60-90 minutes

Standard Profile(sizes in mm)

ReportsA. Sound insulation.

TNO Institute of Applied Physics report no. 006.430 of 04.06.1980.TNO Institute of Applied Physics report no. 910058 of 30.01.1991.Fraunhofer Institute Stuttgart reports of 27.09.1993.

B. Fire resistance.Centre for Fire Research TNO report no. 94-CVB-R0645 of04.05.1994.Centre for Fire Research TNO report no. 94-CVB-R0646 of10.05.1994.C.S.T.B. Paris proces-verbal de classement no. RS99-12 of31.05.1999.

C. Load-bearing capacity.TNO-Building and Construction Research report no. 99 con-Bis-R5006/2 of 01.05.2000.

D. Inter-connected flooring.TNO-Building and Construction Research report no. B-88-078/63.6.1219 parts 1 and 2 (adapted) of March 1989.

E. Physical propertiesTNO-Building and Construction Research report no. 95-BT-B-0763 CRC/ZTO of 17.08.1995.

F. CertificationKOMO (KIWA) Netherlands no. K7470/04 of 01.01.2001.CSTB France no. 3/95-269 of 05.10.1995.ATG (Butgb) Belgium no. 95/2096 of 28.11.1995.BAM Germany no. Z-26.1-41 of 1996.

UNDERFLOOR HEATING ON TIMBERThe usually synthetic piping system is mounted on the upper fluteof the LEWIS® sheeting using clips and drill point screws. A minimum20 mm of concrete measured from the piping should cover the sheeting.It is important that roughly 10 mm of space is kept free between the perimeter of the concrete floor and the surrounding walls toallow for expansion of the floor.

Fields of application❒ Sound and fire resistant floors separating

compartments in residential flats.❒ Sound and fire resistant floors separating

domestic dwellings from public facilities such as pubs,discothèques, restaurants, cinemas, theatres, offices,production areas, classrooms, conference rooms andhotel accommodation.

❒ Fire resistant floors for high-risk areas such as central-heating installations, museums, computerrooms, archives and storage spaces for inflammable materials.

❒ Water resistant floors/tiled floors on timber inbathrooms, toilets and kitchens.

❒ Underfloor heating on timber.❒ Floors of recreation areas and other rooms having

ceramic tiles, terrazzo or flat natural stone as floorcoverings.

❒ Raised high-stability floors for creating, or whereappropriate levelling out height differences in themodernisation of buildings - mainly of concretestructural design - such as shops, restaurants andoffices.

❒ ‘Inter-connected structure’ for floors with inadequate strength and/or rigidity.

❒ Special floors for table constructions used for large-scale models, platforms etc. etc.

35

25 39 25

35

25,5

16

29

dB

70

60

50

40

30

20

10

dB

80

70

60

50

40

30

20

Luftschall

Trittschall

125 250 500 1k 2k 4k 8k

125 250 500 1k 2k 4k 8k

Frequency (HZ)*Airborne sound values

R’w = 36 dB

R’w = 56 dB

Frequency (HZ)

No

rmal

ized

im

pac

t so

un

d p

ress

ure

lev

el (

L’n

)So

un

d r

edu

ctio

n i

nd

ex (

R’)

bare wooden floor:

insulated floor:

*Impact sound values

L’nw = 75 dB

L’nw = 49 dB

bare wooden floor:

insulated floor:

According to section E of the Building Regulations 1991(Reference1) the requirements for compartment floors separating dwellings are as follows:

individual values dB mean values dBairborne sound Dnt,w ≥ 48 ≥ 52impact sound Lnt,w ≤ 65 ≤ 61

.....

Bar

e w

oo

den

flo

or

and

pla

ster

bo

ard

cei

ling

___

Wit

h L

EWIS

flo

atin

g f

loo

r co

nst

ruct

ion

----

sh

ifte

d r

efer

ence

cu

rve

*All

valu

es a

s d

eter

min

ed b

y th

e TN

O In

stit

ute

of

Ap

plie

d P

hys

ics

in t

hei

r La

bo

rato

ry in

Del

ft. T

hes

e ar

e o

nly

eq

ual

to

th

e q

uan

titi

es

Dn

T,w

an

d L

nT,

w a

s u

sed

in f

ield

mea

sure

men

ts f

or

roo

ms

wit

h a

cei

lng

hei

gh

t o

f 3

m a

nd

a f

loo

r sp

ace

of

10 m

2 .

Impact sound dB

Airborne sound dB