ᐅ Should a cavity barrier membrane be placed on the first layer of masonry?

Hello everyone,

Is it no longer common to place a membrane on the first layer of masonry?
So, on the base slab there is the sanded damp-proof course, then the block (calcium silicate brick or aerated concrete), and then another membrane on top of the block? Or is this no longer common? If so, why not?

Regards

This cannot be answered in general terms. It depends on the load. If the wall above the foundation slab is not exposed to any moisture, you do not need an additional vapor barrier.

That means I would need an additional vapor barrier in the wet rooms?

No. It concerns moisture exposure from the outside, either from the ground or splash water. In bathrooms, etc., waterproofing is done from the inside, generally and simply put, for example by the tile installer.

Ah, okay. Thanks!