Over the years I have occasionally done suspended rc slabs for extensions where the engineer and/or building inspector have asked for pocketing in of the slab into the existing building.

A friend of mine caught the idea and now runs his own business. He always pockets in and for tiled floors crossing between old and new finds that sitting the slab on the old wall foundations where the break through is don is the only way to avoid getting cracked tiles.

Recently a LA inspector has refused to accept this method saying that they want to allow movement of the non structural floor of the new extension and the original building.

comments please

He won't allow it to sit on existing house wall and the slab would definitely settle a tad.

If slab runs onto wall, a 9" solid wall then no movement, effectively he is wanting to do a rc ground bearing suspended slab.

pocketed in to new and old all round and all door openings, now it only moves if foundations move

if it wasn't pocketed in

they do put an A142 grid in, probably the middle of the oversite will not go down at all (no blinding) possible tiny deflection of slab possibly none

Good idea, I think they might do that but then the BI will want calcs:(