Clay soil foundation - will foundations for extension need to be deeper because of shrinkage?

Hi Tony, Up here in Stoke (the potteries), most of the soil is clay. In the vast majority of cases, a 1 metre depth is sufficient. However, you say that you had a tree removed on the advice of your structural engineer, if that is in the vicinity of the proposed extension, then you may well have to call in your structural engineer again. Daft as it sounds, when you take down a tree, the root systems are like arteries and they still draw the water, but because the tree is not there it has nowhere to go, so the soil expands and you get what is called a land heave. Hope this has helped Graham