What kind of foundation do I have here?

[garyo]

I've started digging around my old 1970s foundations to see what's what. I can't work out what the floor construction is. In the first photo below it looks like some kind of stepped floating slab with brick slips on the outer.

In the second photo I dug down and could get under what looks like a shallow strip foundation.

In the third I removed the brick slip and didn't discover anything of note, other than it all looks like a single pour of concrete.

The new extension happens to be around 600mm larger all round, so this lower slab is at exactly the right height and position to resuse as a floor slab if the BCO will let me.

 

[noseall]

Depending where old existing walls are, may have an influence upon how your new floor settles, so it is often better to hoof out the lot whilst the digger is on site. Removal is crucial if you need to do any drain or duct runs etc.

 

[garyo]

Mmm interesting point. There's an old 1 metre square coal-house that'll probably have foundations like that.

It'll be a shame (for my wallet and the environment) to have to pull it all out, but there you go.