General Structural Inspection Letter Report: Two Storey Detached Property (Conversion of Barn to Dwelling)
This structural inspection report was prepared and commissioned under the instructions of our clients, Mr and Mrs Burwell. We have been requested by our client to carry out a general site inspection following concerns of various cracking through the property, located at Hemel Hempstead in the area of figure highlighted below. A single, non-disruptive site visit inspection was conducted on the Wednesday 17th June 2020. The weather condition at the time of the inspection was cloudy and wet.
This report is intended primarily for information and is to be read in conjunction with any other specialist
reports and investigations. In accordance with our standard practice we must point out that this report is based upon our inspection of the premises and any other information made available to us, both written and oral, which we have assumed
to be correct. Structural Engineering Services cannot accept any liability to any third party for the whole or part of its content
any liability to any third party for the whole or part of its content.
Brief Description of The Existing Property
The property is a two storey domestic building converted from stables, originally built around 1890s. The original building was constructed using solid brick and stone façade with traditional cut roof and presumably concrete slab floors. Since then various extension work has been performed namely, conversion to domestic dwelling in early 2000s, extension to rear gable end of the property and the addition of a second floor over the front of the building.
The underlying superficial deposit is Clay-with flints Formation, which is a mixture of clay, silt, sand and gravel. The underlying bedrock geology is indicated to be the Lewes Nodular Chalk. We carried out a non-intrusive general site inspection of the horse barn extension property to assess its structural condition highlighting any potential concerns and recommending any necessary structural repairs.
With regards to external elevations:
- There is noticeable gap between the timber soffit board and the exterior face of the front elevation and the front gable of the building. This is most noticeable at the rear elevation.
- At this level, missing and damaged brickwork are also observed.
- Various hairline cracking have been observed throughout the exterior elevations of the property.
- At the rear elevation wall, poorly created notches are observed on top of the brick and stone walls to allow timber rafters to pass through and connect to the soffit.
- Rear sections of the original stone walls exhibit signs of deterioration i.e. bulging/recessing, relatively small cracking in the mortar and chipped stones. Refer to image 13. Signs of various patching up works are present.
- No signs of blocked or damaged drains have been observed.
- Two large trees, approximately 10-15m high and within 8-9m away from the front elevation of the property are present
- A single root is observed protruding above the ground between the front elevation wall and the tree.
With regards to the interior:
- Various size cracking are observed throughout the property.
- Timber beam supporting original rear gable elevation of the property appears to be twisting at both bearings. Cracking along the underside and the length of the member is present. Blocking above the timber beam appears to be hollow but is possibly supporting timber struts to support the original section of the roof.
- In the kitchen window, adjacent to the pier supporting timber beam, several cracking is observed around the lintel bearing.
- Above the right hand kitchen door there is a diagonal crack propagating from the top of the right hand door corner diagonally towards the ceiling. The cracking is approximately 1mm to 5mm in width and appears to be larger on the top than the bottom.
- Similar pattern of cracking is observed above the sitting room door entrance to the hallway staircase to second floor. The cracking seems to be approximately 1-2mm wide and has been patched previously.
- Again, similar cracking pattern is observed in the ground floor bedroom doorway entrance to the hall way. The cracking extends from the top of the door frame corned to the ceiling. The cracking appears to be larger at the top than the bottom. Crack width approximately 1-5mm and previously patched.
- Diagonal cracking is observed in the ground floor bedroom below the window sill. It has been previously patched and painted over. Similar cracking is observed in the adjacent wall separating the bedroom.
- Cracking is observed along the corner of the utility room walls which extend up from the floor level up to the ceiling. The floor in this location appear to have dropped very slightly.
- The base of buttressing wall separating the kitchen and the hallway shows a diagonal crack that has been filled and painted.
- With regards to the timber frame, the posts appear to be moving away from the masonry. The cracking is present on all sides of the two timber posts and vary in width from 1 mm to 5mm. A lot of holes are observed in the timber posts and may be indicative of wood worms.
- The timber beam appears to be in fairly deteriorated condition with similar holes identical to the holes in the posts but far less in numbers. Various cracking is observed in the timber and along the top interface with the plaster.
- Horizontal crack is observed in the living room between the windows. The crack has been filled and painted.
Despite the age of the building, the external structure appears to be in relatively fair condition. The cracking that has occurred in the areas highlighted above, are relatively minor, as defined by the BRE Digest 251 – Assessment of damage in low-rise buildings, which can be easily repaired with repointing. The stone façade should be repaired using lime-mortar (or similar) to match the existing.
It should be noted that the property is situated above superficial deposits which contain both clay and granular material such as sands. Although, we have not observed any leaking drains it should be noted that damaged drains can cause the erosion of granular material and potential result in settlement of the foundations.
Two large trees, approximately 10-15m high and within 8-9m away from the front elevation of the property are present. A single root is observed protruding above the ground between the front elevation wall and the tree. Therefore, it is possible that due to the size of tree, its proximity to the property and the ground conditions are causing seasonal ground movements. Refer to suggestions
The internal structure is in relatively poor condition. The cracking that has occurred in the areas highlighted above, are relatively minor, as defined by the BRE Digest 251 – Assessment of damage in low-rise buildings, which can be easily repaired with repointing. However, the similar cracking pattern near the door way corners (in the kitchen, the lounge and the ground floor bedroom) extending up towards the ceiling may be indicative of ground movement due to the ground conditions and the proximity of large trees. Cracking in these locations can be left untreated and monitored for movement over time. Alternatively, the cracking can be repaired using crack stitching. However, further exposure works are proposed in the suggestions section of this report to ensure no structural damage is present in the foundations.
The timber beam in the kitchen is likely to be warping due to moisture and dampness, causing the timber to expand and contract. Gaps between the soffit boards can be filled using suitable material i.e. brickwork, mortar, expansion foam, etc. to ensure weather tightness.
Cracking around the kitchen window adjacent to the timber beam pier are indicative of inadequate lintel bearings. Lintel to be exposed, assessed and possibly replaced.
The cracking along the timber frame in the living room can be left untreated or treated using normal decoration as defined by the BRE Digest 251 – Assessment of damage in low-rise buildings, but are likely to reappear due to seasonal movements.
- Further investigations could be undertaken to verify the condition of the foundation of the front elevation wall below the ground level.
- We suggest trial holes to be dug at the rear wall, to inspect the foundations and the condition of soil. This would indicate whether significant localised settlement is occurring or whether there is a noticeable presence of tree roots below the base of the foundation.
- We also recommend having the drains checked by a specialist, where they would scan the drain lines by a CCTV survey to determine their condition and fixed as necessary.
- An arboriculturally report could be undertaken by a tree specialist to determine the influence of the removed tree in your property and the two large trees in your neighbouring property. Their surveys may indicate and advise, for example, on the potential risks of the removed tree near the kitchen window. They may suggest using tree root barriers made of high-density polyethylene to protect your property, if you are unable to remove the trees or provide suitable structural solution.
- If ground or foundation movement is found subsequently, an appropriate structural remedy would be necessary. Either cellular structures could be installed beneath foundations and ground floor slab to reduce the downward movement. Underpinning could also be necessary where the soil itself is prone to settlement to stabilise the structure.