Buddywiser

Thanks George, did you do 100mm below slab but nothing as an upstand just concrete to the outside skin with DPM etc, just trying to picture it. You answered nother question on location of Bifold door being on outer skin although I have two 100mm square section posts in the cavity with an A Frame, wasnt sure how the head of the door was going to be fixed if the steel frame is sat back from outer skin

Any further advice out there would be appreciated, the builder has only done a single skin wall, is this ok or must it be a cavity, would be great to get some thoughts before the slab is filled in.

Thanks PeterW, yes no cavity wall built from foundation just a concrete block outside wall with the slab constructed to this single skn

Hoping for some advice on whether there is an option of just having a single skin wall located under a bifold door and not use a double skin cavity etc. This will be the outer wall with the usual inner hardcore, insulation and concrete slab being taken to this wall.