Cavity and solid wall junctions

[davemason23]

Hi, need advice on joining a cavity wall (at right angles) to an existing solid purbeck stone wall. Not sure how to prevent moisture from tracking to internal wall of cavity. Can I grind a vertical slot and insert a DPC or is there another pratical solution. The Purbeck stone is an existing external wall of a property. Infact it is a cavity wall but the purbeck is at least 8" thick and I am not keen to cut a vertical cavity right through. What other ways can I satisfy B. Regs?

Many Thanks

 

[fastneattrowel]

Hi, need advice on joining a cavity wall (at right angles) to an existing solid purbeck stone wall. Not sure how to prevent moisture from tracking to internal wall of cavity. Can I grind a vertical slot and insert a DPC or is there another pratical solution. The Purbeck stone is an existing external wall of a property. Infact it is a cavity wall but the purbeck is at least 8" thick and I am not keen to cut a vertical cavity right through. What other ways can I satisfy B. Regs?

Many Thanks

noseall a know

 

[Shytalkz]

You will have to form a cavity to line through with the cavity to the new work, so that there is a complete break from outside to in. If you merely put a vertical dpc into a slot any moisture penetration can still go from outside to in via the intact stone work, around the side of the vertical dpc. Also, without a cavity, you will get cold bridging, which in these save-the-planet days is a big no-no....

 

[^woody^]

Whilst the 'correct' thing to do is insert a vDPC, moisture will have to be going some to soak through the stone, and what will be effectively a distance of what, 300mm - the thickness of the cavity wall?

Moisture will not travel very far horizontally so a more practical solution would be to line or paint a 400 or 500mm strip of wall in the corner so that any moisture will not emerge on the internal face imediately in the corner, and it will not travel as far as the end of the lined or painted strip. Use polythene or a waterproof compound/paint.

 

[Shytalkz]

Whilst the 'correct' thing to do is insert a vDPC, moisture will have to be going some to soak through the stone, and what will be effectively a distance of what, 300mm - the thickness of the cavity wall?

Yes, but have you ever tried that line of reasoning with a BCO??!

 

[^woody^]

I'm ever optimistic