Sun, 03 May 2026 14:15:10 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=635&Focus=6304#Comment_6304 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=635&Focus=6304#Comment_6304 Wed, 05 Sep 2007 09:42:15 +0100 cornishben We've recently excavated an old stone/cob fireplace in our cottage which was hiding behind a thick 1960s concrete eyesore.. As it's an old cottage it doesn't have any kind of DPC and the construction is granite/earth on the lower half and cob on the upper half.

Hence, the backs/sides of the fireplace are granite/earth, which I have lime rendered. The hearth base was just earth/stone, which I have (perhaps not wisely) laid a 2-3inch concrete bed on.

We are now looking to lay some slate on this concrete but the concrete is damp and there seems to be dampness creeping up the plaster at the back/sides, up to 4-5inches high. I guess this is because basically its just earth underneath..

I'm wondering what I can do about this?!

Could I bitumen or damp proof the concrete base somehow, before laying the slates. Which may resolve the problem of a damp base, but if so, would i need to cut into the base of the sides to insert the DPC or something in order to stop the dampness rising up the sides?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=635&Focus=6308#Comment_6308 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=635&Focus=6308#Comment_6308 Wed, 05 Sep 2007 12:22:49 +0100 tony
The slate will form a damp barrier itself

In a fire place you should not need much in the way of damp proofing -- in any case do not use bitumenous stuff it will stink and may catch fire ,it also contains carcinogens.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=635&Focus=6328#Comment_6328 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=635&Focus=6328#Comment_6328 Wed, 05 Sep 2007 19:52:21 +0100 Gervase Webb https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=635&Focus=6365#Comment_6365 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=635&Focus=6365#Comment_6365 Thu, 06 Sep 2007 15:41:02 +0100 cornishben
We're planning to put a large piece of Delabole slate in over the base, so maybe I can just get away without replacing with limecrete and just plonking the slate in and forgetting about it.. I guess it'll dry out when the woodburner is lit]]>