foundations on the clay soil

[saravakos]

Hello there, I would like to build 2storage extention, but aprox 300mm deep there is
thick dark yellow clay. Does anyone know or have experiance?
How to support concrete foundations, with hard core? Please help. Thanks

 

[noseall]

You would typically dig down to virgin clay, usually 1m deep then pour concrete directly onto the base of the trench.

However, there are more things to consider like nearby trees and shrubs etc as well as the possible need for clay heave barrier.

Has the foundation been designed? You will still need to get the trench inspected and approved via the local authority, regardless.

 

[JohnD]

Hello there, I would like to build 2storage extention

You mean two storeys high?

Will you be building it yourself? You will need Building Regulations approval of your plans. the BCO will doubtless have seen many similar jobs locally, and will know what they normally require, you could phone and enquire. It is often informative if you can see similar plans on the council's website, which you can look at free.

The foundation of an extension will normally be the same depth as the house, but an old house may have shallow foundations, so the new one will be deeper. On deep clay, especially in London. there is a considerable risk that the house and the extension will move about differently depending on weather, and may become separated by a noticeable amount.