Structural Engineers Report - ESDMhbsmrgateway2.esdm.co.uk/norfolk/DataFiles/Docs/AssocDoc... · 2008. 5. 15. · Consulting Civil and Structural Engineers 68D Swan Yard King Street

Consulting Civil and Structural Engineers 68D Swan Yard King Street Norwich NR1 1PG

Tel 01603 760588 Fax 01603 760598

e-mail: [email protected] www.theburrellpartnership.co.uk

Structural Engineers Report

For

Brown & Co

Old Bank of England Court

Queen Street

Norwich

NR2 4TA

Regarding

Bergh Apton Hall Barn

Bergh Apton

Norwich

Norfolk

10 May 2007

Consulting Civil and Structural Engineers 68D Swan Yard King Street Norwich NR1 1PG

Tel 01603 760588 Fax 01603 760598

e-mail: [email protected] www.theburrellpartnership.co.uk

Our Ref: DJQ/MJB/1449 Date: 10 May 2007

Your Ref: KJS/DNHH/7210/JY

For the attention of Keith Sewell Esq

Brown & Co

Old Bank of England Court

Queen Street

Norwich

NR2 4TA

Dear Sirs

Re: Bergh Apton Hall Barn, Bergh Apton – Freeman Executors

We refer to your recent kind instructions, for which we thank you, and having visited the above

property to carry out certain investigations, now submit the following report.

We understand the extent of your instructions to be to carry out a structural assessment of the

barn to give a general structural overview and more specifically with regard to it’s conversion to

a habitable living space. The content of this report is thus so confined.

We have not inspected the woodwork, or other parts of the structure which are covered,

unexposed or inaccessible, and we are therefore unable to report that any such part of the

structure is free from defect.

Cont…

Page 3 / continuation/ DJQ/MJB/1449/ 10/5/07/ Brown & Co

1.0 Description of Premises

1.1 Briefly, the barn comprises a timber framed structure with the walls built off a masonry

plinth approximately 600 mm high around the perimeter of the building. The walls

above the plinth consist of timber studs and shiplap boarding. The roof is relatively

steep at around 45 to 50 degrees and is currently clad in corrugated sheeting. Support to

the roof is provided by a number of principal trusses which generally take a collar and tie

formation, although the collar and tie do not always occur on the same rafter. The

principal trusses carry purlins which in turn support the common rafters. Generally the

roof trusses are carried on vertical posts down to wall plate level, with a knee brace at

the eaves junction.

1.2 The barn comprises one of a series of agricultural buildings in the immediate vicinity.

These are of varying materials and constructions.

1.3 The site is gently sloping and surrounded generally by farmland and woodland.

1.4 The age of the property is not known, we estimate however that it is at least 100 years

old and probably significantly older.

1.5 Given its past usage, whilst surface water drainage was noted by the presence of gutters

and down pipes no foul drainage system is anticipated.


2.0 Description of Defects

2.1 The defect in respect of which our advice has been sought is to comment upon the

general condition of the barn in respect of its structural robustness as well as its

economic viability into converting the building for domestic use. The content of this

report is thus so confined.

2.2 The agents acting on behalf of the applicant have produced survey drawings. It is our

understanding that Architect’s proposals are currently being prepared.


3.0 Investigations:

3.1 An exploratory trial hole was not considered necessary since given our local knowledge

of such properties, together with their known date, the most likely foundation would be a

nominal brick outstand constructed between 150 and 300 mm below ground level.

3.2 At the time of our visit, a visual inspection was carried out and a series of photographs,

which are appended to this report, were taken with their descriptions being set out below.

Photograph Nos. 1-10 inclusive – show the external elevations around the property,

indicating the timber clad main barn structure and corrugated sheeting to the roof.

Photograph No. 11 – highlights the presence of guttering and downpipe to the west

elevation, showing also missing cladding boards. This elevation was generally

inaccessible due to overgrowth of vegetation.

Photograph No. 12 – indicates the broken lintel over the main entrance to the barn.

Photograph No. 13 – further showing missing cladding to the west elevation. The

plinth beneath the post adjacent to the opening is collapsed locally, requiring repair.

Photograph No. 14 – indicates cracked blockwork to the plinth.

Photograph No. 15 – shows insect damage to a timber stud as part of the external wall.

Photograph No. 16 – is an interior elevation on the north gable wall showing the

generally sound construction. The collar and tie principal trusses can be seen in addition

to the knee braces and diagonal wind bracing to the gable wall.

Photograph Nos. 17 & 18 – show details of the eaves and general roof construction

including double purlins and common rafters. Note the steel tie rods inserted through

the wall plate at eaves level.


Photograph No. 19 – highlights the valley to the main roof from inside. Generally the

roof is reasonably sound, however a damaged timber beam is visible to the right of the

picture. The dowelled splice joint has failed and an acrow prop has been installed to

prevent further damage.

Photograph Nos. 20 & 21 – show further details of the damaged timber beam over the

opening into the rear of the barn.

Photograph No. 22 – shows the internal elevation on the eastern gable wall to the rear

of the barn. Again indicating the generally sound condition of the timber frame.

Photograph No. 23 – shows the internal elevation on the southern gable wall. Whilst

the walls are missing areas of cladding, the sound condition of the original timber frame

is clearly in evidence.

Photograph Nos. 24 & 25 – these are taken looking up into the roof. Daylight can be

seen which will let in rainwater and ultimately could damage the timber frame.

Photograph No. 26 – shows a view looking east to west.

Photograph No. 27 – highlights the broken lintel over the main entrance.

Photograph Nos. 28 & 29 – indicate a missing section of the brick plinth internally

which requires repair.

Photograph Nos. 30 & 31 – show the extent of the attractive original timber framework

Photograph Nos. 33 – 35 inclusive – detail damage to the timber wall plate and brick

plinth on the western elevation due to water ingress and general disrepair.


4.0 Discussion

4.1 The timber frame appears to have been largely untouched since construction and as such

retains much of its original character. Generally the frame appears reasonably sound

although evidently piecemeal repairs have been carried out at various times to small

areas of the building, whilst other areas have obviously suffered at the hands of time.

4.2 Some areas of the external cladding are missing (photograph nos. 11 & 13),

predominantly to the southern and western faces of the building which has allowed the

ingress of both water and vegetation. An obvious result of this is both the growth of

mosses etc on the timber wall plate on these elevations, in addition to several sections of

wall plate and timber studwork which are badly rotted (photograph nos. 33 & 34). Left

unattended this situation will only worsen.

4.3 In addition to the rot mentioned above, sections of the timber wall plate and a number of

the timber studs forming the external walls have been attacked by insects (photograph

no. 15) and some sections will require treatment or possibly replacement by skilled

craftsmen to ensure that the original character is retained.

4.4 The roof, whilst generally appearing sound, does show daylight through a number of

small openings which will allow penetration of rainwater. Over time this may have

serious consequences for the internal timber frame.

4.5 The masonry plinth is in a poor condition in places and in some locations will need to be

repaired or re-instated (photograph nos. 28 & 35). Cracking is evident to a portion of the

plinth which has been re-built in blockwork (photograph no. 14). This would appear to

indicate some degree of structural movement in the past, which is not surprising in a

structure of this type.


4.6 The timber lintels over the main opening into the barn and to the opening into the rear

portion of the barn have both split and badly deflected (photograph nos. 12, 20, 21, 22 &

27). This appears to be due to overstressing of the timber rather than weakening due to

insect attack or rot. As a result of this, the ridge of the roof has sagged in a

corresponding position (photograph no. 3). The lintel to the rear is currently supported

on an acrow prop (photograph nos. 21 & 22).

4.7 Whilst the effectiveness of the roof drainage is not known, it can be seen that the

guttering over the main entrance is displaced due to the damaged lintel. It is most likely

that large amounts of water will spill onto the ground at this point, creating problems

associated with saturation of the adjacent soil such as foundation movement, in addition

to the obvious problems associated with concentrations of damp as discussed previously.

4.8 As stated previously, a number of the structural timbers throughout the building show

signs of rot and insect attack and as such will require treatment to prevent further

damage, and in severe cases replacement. It should be noted that the structural integrity

of the timber frame has been compromised by this attack and additional loading would

not be advised on the existing frame. Should it be proposed to tile the roof then careful

consideration will need to be given to carrying the additional load that this would place

on the structure.

4.9 Considering the conversion of the barn there is sufficient space to allow for an

intermediate floor in order to provide first floor accommodation. It would therefore be

our recommendation that an independent timber frame, constructed in sympathetic

materials and style, is utilised to support a new first floor construction. This independent

frame could then be used to provide a stable platform to introduce lateral restraint and

enhance the stability and robustness of the existing structure. This would be not only

beneficial to the structure as a whole but would have the added advantage of placing any

further loading onto new foundations, leaving the existing frame to enjoy its senior years

in relative comfort.

4.10 As stated previously, the existing foundations are in all probability constructed with

shallow brick outstands.


4.11 The foundations in this case are relatively modest by current standards given the ground

conditions encountered are for a clay subsoil which can be problematic. Clay soils have

the property of volumetric change when changes in the moisture content occur.

Reduction in moisture content produces shrinkage of the soil. When moisture content is

taken up subsequently, then the soil expands, and this process is defined as heave.

Therefore, any foundation formed in such soils will consequently experience movement,

with this movement being generally reflected in the construction above. Reduction in

equilibrium moisture content in such soils can be induced by natural climatic change,

such as periods of drought, or induced by root action of trees and shrubs. Not all clay

soils exhibit the same amount of volumetric change and the amount will be dependent,

also, on whether the soil is a pure clay, or a mixture of clay and other soils, such as sand,

which do not exhibit such properties. The degree of volumetric change which can be

induced by trees and shrubs is dependent upon the species of tree, together with its

proximity to the foundation. Each circumstance is individual and a bespoke design, and

it is therefore normal practice to refer to the NHBC standards and guidance. In the

absence of trees or shrubs, the foundations still require being formed at a greater depth

than would be the case on sands and gravel’s, in order that they should not be at a depth

below the depth which normal desiccation can occur during periods of drought. Current

interpretation of Part A to the Building Regulations is such that the foundation should be

founded not less than 0.75 m below ground level.

4.12 However, at the time of our visit to the property there was little evidence to suggest the

barn was suffering unduly as a result of shallow foundations. In the circumstances, we

do not consider the need to enhance the existing foundations by underpinning and we

would not expect any further movement due to initial building settlement given the

passage of time and that domestic floor loadings are considerably less than agricultural.

Thus, providing suitable drainage for both foul and surface water is introduced and

advice with regards to planting of trees in proximity to buildings in clay foundations is

observed in accordance with Chapter 4.2 of the NHBC recommendations, we have no

further comments to make.

4.13 In addition, an adequate foul and surface water solution will need to be derived but this

is all considered to be within normal building practice and not prohibitive.


4.14 It has been within our wide experience that a sympathetic approach for a conversion of

the barn into residential occupancy will give an opportunity to enhance the structural

robustness and integrity of the barn without destroying the character of the property or its

visual impact on the surrounding area.

4.15 Further, this window of opportunity would eliminate any out of character adornments

such as mismatched brickwork and therefore considerably enhance and extend the useful

life of the barn, without widespread renewal or replacement of structural elements.

4.16 Whilst outside the scope of this report, we consider it worth noting that the architectural

scheme will need to satisfy Part L of the current Building Regulations in terms of

insulation and thermal performance.

4.17 Overall, renovation of this barn provides the opportunity for the restoration and retention

of a fine timber framed barn in an attractive location. Whilst the building is not without

its defects, we would consider that sympathetic repairs coupled with the addition of a

new independent structural frame would provide an economically viable method of

providing a habitable living area within the existing space.

We submit this Report to you at the present time, and for any further instructions you may have

for us in this regard.

Yours faithfully

David J Quantrill BEng

On behalf of The Burrell Partnership

John R Illingworth CEng, MIStructE

On behalf of The Burrell Partnership

DJQ/MJB/1449

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Documents

Structural Engineers Report - ESDMhbsmrgateway2.esdm.co.uk/norfolk/DataFiles/Docs/AssocDoc... · 2008. 5. 15. · Consulting Civil and Structural Engineers 68D Swan Yard King Street