Do I need a cavity wall in the footing of a ground bearing slab or is it just for a suspended slab

[Skeff]

Do I need a cavity wall in the footing of a ground bearing slab or just single brickwork and start cavity on top of slab and is it just for a suspended slab you need an inner leaf

 

[^woody^]

No you dont need a cavity wall below, but you can't start a cavity wall on a slab unless its designed to take it.

 

[Skeff]

It’s for a single storey extension
Will I need an inner leaf

 

[^woody^]

The old chestnut "what do the plans say?"

It all depends on the design.