Vapour control layer in a breathable stud wall?

[jconnolly]

I have just had a chimney breast removed leaving in its place a single skin of external bricks. I have been told I should build a stud wall to fill this gap. My plan is the following:

• External bricks
• 10mm gap
• Stud wall
• Insulated with sheep's wool
• Wood wool boards
• Lime plaster

Would I also need a VCL, or is that pointless if all materials are breathable? If I do, what material should I use, and where should it go?

Bonus question: Any suggestions on how to maintain the 10mm gap between external bricks and the sheep's wool. Mesh? Battens?

Thanks!

 

[malcolm]

I've been avoiding unventilated air spaces in my walls. You never know what is growing in them. If the outside of the wall is breathable (not cement pointed or masonry painted) could you not just screw a 4 inch woodfibre board on there and lime plaster over it? No need for studs if you aren't supporting anything on top. The woodfibre board would best be held off the ground by a few bits of slate just to avoid it sucking up any moisture down there.

 

[jconnolly]

Thanks Malcolm that's an interesting idea. I guess following this logic, the ideal (putting time/cost aside) would be to rebuild the inner skin of bricks. The single skin is actually just on the first floor, so I'm not concerned about sucking up moisture from below. Unfortunately it is cement pointed, but not painted. It will likely always be cement pointed, as that face of the wall is in the neighbour's garden directly above a conservatory running all the way to the wall, so almost impossible to access. The main reason the chimney was removed in the first place is that external maintenance is hard and costly.

I think as I already have all the materials and plan to do this on Friday I will likely stick with my plan above and hope that by keeping all layers reasonably breathable it avoids mold. I think that probably answers my own question about VCL.