Waterproofing

[denso13]

Blockwork doesn't need protected, unlike a timber frame.

 

[DiyNutJob]

Too expensive? Nothing to stop you adding membrane.

 

[denso13]

Blockwork is porous

So what? Blockwork doesn't need protected from moisture.

Even for timber frame the vapour barrier would be on the warm side (inside), not in the cavity.

 

[denso13]

For water penetration

No, not required, it's a ventilated cavity behind a waterproofed facade.