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Structural Engineers Report example

We were asked to attend and report on a local property in Wimbledon Village SW19  as a matter of some urgency as cracks of nearly 100mm were noted ( Four inches).

 

Engineers Report findings

Sudden and quite serious subsidence had occurred to a detached garage on the slopes of Wimbledon Hill. Fortunately the main house was ok.

The entire structure leaned by over 100mm as a result of significant shrinkage ( desiccation) of the London Clay soil due to a large tree nearby. This occurs when London Clay, which is some 90% water, shrinks during periods of draught when thirsty trees extract more ground water than normal. The resulting moisture extraction causes a reduction in the volume of the soil for the top 1-3m depending on the depth of the tree roots and tree species etc, with consequent loss of support to any structure above. Note this is quite independent of any weight loading so subsidence does not differentiate between the ground beneath a heavily loaded 3 storey house and a lightweight conservatory structure.

The structure was demolished and rebuilt on piled foundations. It was uneconomic to repair as the distortion was too great that roof drainage and general appearance was compromised.

The neighbouring tree was of considerable amenity value and was outside the control of the subject property so had to remain in place. This left no alternative but to rebuild the entire structure and on much deeper foundations which would not sever the tree roots and harm it. This inevitably led to the use of piles ie localised deep cork screw legs deep into the ground below the tree roots where the supporting soil is more stable year on year.

Posted in Surveys/ Reports

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Pole Structural Engineers, Admel House,
60 High Street Wimbledon London SW19 5EE 
Tel: 020 8944 9955
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