In article ,
"Christian McArdle" writes:
I always thought you had to use engineering bricks in foundations (I'm
not disputing what you say, just never heard of Celcon Foundation!)

Nah. Most concrete blocks (including aerated) can be used in most soils, at
least according to the manufacturers. But you should check the particular
combination of soil and block.

Strange, as the thermal blocks used for internal walls will expand
when they get wet and contract again when they dry out, which sounds
like it would be really bad news in foundations below the damp proof
course. (You have to be careful plastering them for this reason.)

--
Andrew Gabriel