May 23May 23 Hi, My builder has just used cement to fill the join between the two walls. The cavity block wall and the stone, rubble and lime mortar wall. I can see the damp penetrating the blockwork but the lime mortar wall dries well as it should. Can someone advise what I should expect for this area of the construction? I can’t see this as being acceptable. Photo provided.
May 25May 25 Why is it damp? how else is it going to be constructed? once the block wall is weathertight what is the issue?
May 26May 26 Author On 25/05/2026 at 12:21, jfb said: Why is it damp? how else is it going to be constructed? once the block wall is weathertight what is the issue? Hi, I’m led to believe that a vertical DPC would normally be used between a cavity wall and the original building’s wall. I think the damp is leaching from the stone wall with lime mortar into the block wall. Ther’s not a lot of definitive information readily available. Thanks, Robert
May 27May 27 21 hours ago, RobertG said: vertical DPC would normally be used between a cavity wall and the original building’s wall On the inner leaf of the new wall - if you want something to show your builder then LABC publish renovation guidance that covers this including a diagram on page 14...
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