There are a few reasons for subsidence affecting building foundations Clay soil. In the UK clay soils formed by the deposition of tiny rock particles along the beds of historic rivers, locking a certain amount of moisture within their matrix. Moisture will often stay locked inside clay for many decades, providing the clay is not exposed to excessive dehydration. When clay does dry out, it begins to shrink. When it is moistened again, the clay expands. Because this cycle is repeated every year, clay shrinkage and expansion usually goes unnoticed without causing any ill effects. It is during extended periods of drought that the cycle can be interrupted, and that is when things begin to go wrong. Tree roots can be a huge problem, as in a drought situation they are prone to branch out in search of moisture . When the roots drain the clay dry, shrinkage takes place and disaster can ensue if the soil in question is beneath a building`s foundations. Mine workings and instability of uneven ground are can also be likely causes of subsidence. In some cases the most cost effective way of dealing with buildings damaged is to underpin the, in extreme circumstances the whole building will have to be demolished and rebuilt. it is important to make sure your buildings insurance c overs building damage by subsidence.
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