Wales · answered by Verika · verified against sources
How deep do strip foundations need to be in Wales?
"In clay soils subject to volume change on drying (‘shrinkable clays’, with Modified Plasticity Index greater than or equal to 10%), strip foundations should be taken to a depth where anticipated ground movements will not impair the stability of any part of the building taking due consideration of the influence of vegetation and trees on the ground. The depth to the underside of foundations on clay soils should not be less than 0.75m on low shrinkage clay soils, 0.9m on medium shrinkage clay soils and 1.0m on high shrinkage clay soils, although these depths will commonly need to be increased in order to transfer the loading onto satisfactory ground, or where there are trees nearby (including consideration of proposed planting of trees) ." [2]
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