I'm building an extension (DIY) and I'm a bit unsure about the inner skin around the door opening. I've gone single skin for the door openings but I've realised that a lot of people seem to have it coming up to around 1 block (225) below FFL. I've attached a picture to show the two options. That's my build up in the picture (150 hardcore, 50 sand, 150 concrete, 150 PIR, 50 screed).
I can't work out what the inner skin does as there is nothing above it that it needs to support, but I can't imagine builders would spend the time/money doing it if it's not required. I would imagine a concrete fill would add strength to the outer skin when the oversite is being done but I would expect that to be fine once the oversite is finished.
I can't work out what the inner skin does as there is nothing above it that it needs to support, but I can't imagine builders would spend the time/money doing it if it's not required. I would imagine a concrete fill would add strength to the outer skin when the oversite is being done but I would expect that to be fine once the oversite is finished.