cavity wall construction

4umbrellas

Hi all,

Are there any regulations governing what the minimum width must be in an external cavity wall made from solid concrete blocks? I would have thought it would be specified in Part A of the Building Regulations, but I can't see anything there.

In the section on wall ties (1.1.3.27), the smallest cavity width that's mentioned is 50 mm, but does that mean that a cavity width smaller than that is not allowed?

Also, are there any circumstances where it would ever be legally possible for foundations only to be beneath a wall, without projecting at all on one side? I.e. foundation might be like this (where X shows wall and foundation), and foundation doesn't protrude beyond the actual wall at all on one side.

.|.|.|X|X
.|.|.|X|X
.|.|.|X|X
X|X|X|X|X

I can see Part A says that for strip foundations of plain concrete, in no case should the width of the foundation be less than the total width of the wall plus 75 mm on each side, but are there other types of foundations where this wouldn't apply?

Many thanks for any pointers.

Gumbo

Your engineer will advise as if you venture out of the building regs you are now entering a designed section which, as you guessed it, needs to be designed

4umbrellas

Thanks kceire.
Does that mean there are circumstances when the building regs don't apply? This is actually a wall that's already built but it looks pretty shoddy to me and I'm sure it wasn't meant to be built that way. Just trying to find how things stand before deciding what to do.

BryanF

Hi, you need a structural eng. Building regs always apply! Unfortunately we can give you no more advice in this topic as it's site specific and your questions of is of a structural nature which go against the forum charter
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