Damp! Paging @pigletjohn (with photos)

[nightmarepickle2025]

We’ve had a damp problem in our bay window for a while. Have now had the plaster taken off as it was perished. So we can see clearly where the damp is coming in. The idea was to tank it and replaster but the damp is coming through the tanking coat so that’s not going to work until we fix where it’s coming from.

There are no pipes nearby, though the roof is concrete and has no rainwater goods - the water just drips down from a ledge, which probably isn’t helping but there’s nowhere to attach a gutter too. And it was built like that 130 years ago.

The previous owners also had the house repointed with cement mortar, not lime, so also not helping.

But it looks to be coming through the windows - which are PVC and we’ve had resealed with mastic so there’s no obvious place where the water is coming in.

The stone sills are crumbling - could water be getting in through them?

There is a black stain on the wall in your last picture. Can you take a pic from further back showing the roof of the bay please?

Are all your neighbours bay window roofs the same as yours?

I think is could be an issue with the bay window roof.

Neighbours houses are not the same construction. Looked at the roof and there do seem to be some cracks where it joins the wall

Have you no damp at first floor level?

If the damp is at ground floor level only then you may have rising damp. They used to put slate as a damp proof course in brick at that time so maybe your house doesn’t have it in the bay window but even if it does it can can get degraded and damaged over time giving damp at ground floor level.

The first floor bay is also damp. We’ve had a new dry rods put in on the ground floor and the area closest to the ground isn’t damp, so I don’t think it’s rising.

(Thanks both for taking the time to comment, appreciate it!)

Ah then ignore that so as the other poster says the roof or potentially the cracking along the wall.

There might be some flashing at the roof level damaged or the roof finishes themselves might have given out.

I do remember the immortal words of my uni lecturer many decades ago which you won’t want to hear as a home owner. He said that flat roofs were so good for our industry, we got paid to design them, to install them and inevitably we got paid to fix them when they failed.

That says something about the very common issues with flat roofs in this part of the world particularly with our dire weather so it definitely could be that.

Where does the water from the top roof go?

It just drips down off the edge

The lip stops it running down the walls but the drips do hit the lower sills

Looks like you are in London or near the Thames. The house will have a DPC and I think it will be well above ground level, but it looks like there is a mortar plinth round the bottom of the wall which will hold damp, and, unless you can see the DPC, probably bridges it, encouraging damp.

It's a pity you bought dryrods, I could have sold you some Magic Beans which would be equally effective.

It needs a gutter and downpipe.

would removing/ replacing the plinth help? The indoor floor level is 2 bricks above the plinth

BTW, when you get a new roof on the bay (it needs it) try to find a sympathetic local specialist who can make a new roof with provision for gutters. If it has been leaking it will need new timbers. If it has old chipboard, fling it in the skip. It is quite small and out of reach of most thieves so you could have lead, but due to toxicity a lot of roofers avoid it now. Synthetic rubber is a good alternative. Zinc has a relatively short life.

Fibreglass should be good, but for some reason often seems to be badly installed by unskilled people. I don't know why. Ask around. If you know any local churchgoers, try to find out who does their Victorian roof. They may be costly but you have a fine house and it deserves a quality job.

Avoid advertising websites where traders pay to be listed and can remove unfavourable comments, even if they masquerade as recommendation sites.

Fixing the roof spillage is more important. Look round the house until you find the DPC. It will be slate. It may well be underneath the airbrick as I can't see it above. It will be at a constant height except I think you are on a hill so it might step up higher.

The bricks might be damaged under the plinth. It is possible to groove it to expose the DPC. I expect it is cement and hard to remove.

Thanks so much for the advice, greatly appreciated