"Trevor Smith" wrote in message
...
We live in a victorian / edwardian terraced house in Cornwall which has
solid granite "cob" walls, a number of which suffer from penetrating damp. A
builder has told us that we may need to have them tanked but it appears that
this is a "trade only" product. Can anyone tell me what it is, how it is
appplied and what the Retail name is. Do Screwfix or e.g. B&Q sell it?
Thanks.

Trevor - before you go off down the tanking route.......

Remember granite itself is totally waterproof, not porous like brick or soft
stone. The only damp part of granite walls is the joints - rainwater runs down
the face of the wall rather than soaking in like it does with softer materials,
and this quickly leaches out the pointing (what you call the cob). I think
you'll find you'll make a really big difference to the internal dampness if you
rake out and repoint the wall properly outside.

This link from the granite city of Aberdeen tells you how to repoint properly:
http://www.aberdeencity.gov.uk/acc/p...onry_notes.pdf

Best of luck
Peter