Conservatory into an extention

thearchitect

snowcat75 said:

thearchitect said:

Have you considered that perhaps you just live in an area with excessively plastic clays?

Incidentally, some blue clays are expansive which can lead to problems.

I'm sited on a 3500 acre shelf pushed here by the ice age which has just over a 100' of ballast bellow a 5" overburden, the 100 acres of historic gravel extraction are a hint, and certainly failing another ice age pushing one of the estuary's over the high ground there's not a drop of clay down there.... but good luck arguing with BC for a 600mm footing.

Here is an extract from the Scottish Building Standard Technical Handbook (small buildings edition)

Here is the extract from BRE Digest 240, from our files, showing the areas where the geology requires deeper foundations:

You will note that the problem clays are geographically restricted, albeit they include major population centres.

So, to be clear, all this handwaving that 1000mm is a minimum is just bunkum.  As I have said already, it depends on soil conditions but 600mm is perfectly normal for most of the UK and Ireland.  450mm may be possible where deep frost is not an issue.