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After throwing money at my house the bloody thing still has a damp gable wall. 3 storeys tall, the damp is evident in the stud wall on the 2nd floor gable end, coming from above. There's no plumbing above it so I can rule that out.
Construction is solid stone wall with brick above. Gable has been newly leaded, ridge redone, brickwork repointed (with lime), new chimney on the top, new chimney pots and new cement to hold the pots on place. Some new bricks used and all done professionally, not DIY.
In the loft (very small) there is no sign of damp on the ridge beam or on the bricks or on any of the insulation. So I'm pretty happy nothing is leaking through the ridge tiles or the lead flashing round the chimney. So, I suspect it's either coming through the wall (possibly through the single brick thick chimney wall) or down the chimney pots or the cement work at the top of the chimney.
Is there any non-destructive way of identifying exactly where the leak is? Someone mentioned a Sarah Beeny programme where someone used a UV visible additive to some water to trace it but I can't see a reference to that anywhere.
Cheers.
How do you define 'damp', is it showing as a stain, or have you had it tested, is the wall finish, plaster, line, or masonry damp. Sorry always more questions, pictures would help? Old building?
Often water may have been entering, especially if exposed gable and/or chimney breast, but also salt contamination can still be within the wall, even after the roof repair has been completed and so stains continue to show up. Hence testing for actual moisture content.
Sounds like you are doing a good job of checking water penetration, check salts and any condensation risk.
Also consider a good local surveyor (by recommendation).
Thermal imaging is another aspect BUT be careful to use a real expert as thermal imaging cameras can give false readings, decent TI cameras cost about the same as a small new car!
Good luck.
Thanks.
Yes, old house. The damp is visible (stain) and stud wall feels clammy to touch. Showing up as a damp stud wall, so plasterboard and wallpaper.
Once we know we have no more guests turning up this summer I'm ripping the stud wall off to get behind it. Damp seems to come down the chimney stack - the stud wall is damp where it joins the stack.
Definitely not condensation - we know what that is like, and have dehumidifiers all over the place to deal with that.
As to the specific question, I have no idea ... Lots to learn, I think!
It'll most probably be water penetration from the outside, we had a similar issue with our place - in the end I traced it to some flashing that was letting rain in; but only when it was windy...
Soot and salts in the chimney attracting water?
Try a cap on the pots ..?
I take it the chimney is no longer in use? Does the top have a vented cap and is there also an internal vent to allow air to move through it? If not you can get condensation on the inside of the chimney, causing damp. It may well just be from driving rain - if so consider a render or maybe a waterproofing cream (Stormdry masonry protection cream is good stuff).
One chimney not used so has a pepper pot lid on it, the other has a wood burner with metal flue and cowl over the top.
If it comes to it and the moisture is getting in through the wall (porous bricks) I'll get it lime washed. But before I do that I'd like to see if there's any way to pin down exactly where the damp is coming from.
Best is to look closely when it rains as it may give you a better idea where the water is coming from. We have a similar problem after we had the house re-roofed and external insulation put on. Turns out that one of the chimney joins is not water tight so the water runs between the slates and the external insulation and ends up on the wall.