Does anybody know where I could possible get hold of cavity wall
specs ? basically I'm looking at managing a extension project myself
but I want to be sure that everything is done right and according to
BC. Some of the builders I have had in for a quote tell me that for
the floor be it solid or wooden, they have to dig about 8" down and
then build it up with a mixture of hardcore, insulation and DPM, is
this correct ?

Any advice/help will be greatly appericated.