Just to follow up, I scraped up all the moss off the path to reveal a
concrete layer that's actually in good condition and "haunched" up the
house wall all the way along, except for about three foot at the end that
developed damp. (Much easier to see this without the weeds and moss!)
I can't work out why that end has never been haunched but it seems likely
that any sitting water is percolating down between the path and the wall at
On closer inspection, the entrance to the air vent actually has quite a
reasonable slope to shed water so I don't think that it is an issue.
On Monday, 16 November 2015 21:30:04 UTC, Vir Campestris wrote:
It prevents damp rising by capillary action in porous masonry. (It's water repellent)
However, it doesn't make masonry magically waterproof.
So if there's water "dammed" behind a water, it won't hold it back.
You can hire the gear and buy chemical at tool hire shops.
Rising damp is not as common as people think, it's usually condensation.
Or a wall acting as a dam.
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