We have had an ongoing issue with damp in our study near the roof level around the chimney which has been a low level annoyance for about a year and a half now. In investigating the potential cause, we discovered that our shared rear chimney was in a pretty sorry state in terms of one particular area of lead flashing around the base which was missed in an earlier inspection back in June 2016, the brick pointing, the bricks themselves (some of which were split), and some areas of the parapet capping (which you can see here). While rectifying these issues, we ended up rebuilding the whole chimney and reducing it in height (as many had already done on our street) to minimise future risk of collapse (they were all built just a bit too high!).
As a belt and braces approach, we also added chimney caps to all pots (our neighbours kindly agreed to let us put temporary caps on theirs as they aren’t using their rear fireplaces at the moment), and also added in a pair of cast iron air bricks in our 2 flues to allow for some air movement (which I bought from ebay here as they have lots of fancy Victorian patterns!), so if any moisture got in, it could dry out. We couldn’t obviously put air bricks in our two neighbour’s flues as then our house would fill up with smoke if they every used their fireplaces – but as their flues are still open internally – there would still be the opportunity for air movement in all 4 flues.
Well… unfortunately, despite roughly 11 coats of paint being applied over the course of a year and a half, including the initial base coat and 3 top coats to provide sufficient coverage over the existing masonry, two different brands of stainblock paint, and more top coats in between, we still seem to have some discolouration at high level. It doesn’t look like mould luckily… but we are stumped!
We’ve recently had a desk top and shelf built in as part of the nursery/study/ guest room swap around (pics later once we eventually get around to painting them!), and the carpenter who helped us out recommended this Zinsser BullsEye 1-2-3-Primer. Apparently in the building industry it is the go-to solution – so we are giving this one last chance. If this fails, then we’ll call the builder back who did the chimney re-build to see if perhaps a bit of flashing has fallen loose… ooof.
I’m not suggesting this stain block will solve all your damp issues – its always best to find the source of the problem (not always so easy as moisture can track for quite a distance before manifesting) – but apparently this is the best stuff for dealing with the aftermath of staining that keeps grinning through.