Mysterious damp patches

[tittysprinkles]

Another where's the damp coming from thread.

Background - 1930s semi purchased a couple of months ago. One small patch of damp on a back wall near a French window picked up on the survey thought to be due to failed DPC. Another couple of spots on the plastered over chimney breast in the loft thought due to leaking flashing.

All well and good, we are awaiting DPC treatment to rear wall of house near the damp spot (dubious benefit I know) and repair of flashing/repointing of chimney stack.

We are not living there yet as it is being refurbished so have had heating off most of the time. We have been stripping wallpaper, removing skirting and removing some damaged plaster.

This weekend we noticed a new patch of damp in the kitchen which is an extension built onto the side of the house. It is about 1/3 way up the wall above a radiator. Two new patches have appeared at the base of the same wall but about 4m away either side of an arch which leads to a small back porch. I assume the affected wall was previously the external wall of the house.

My question is, could the new patches just be due to condensation? It has been very damp weather and there has been a lot of condensation due to the wallpaper stripping.

We put the heating on and it is starting to dry out. Have had plumber in and no leaks. No obvious blocked downpipes or gutters and roof of extension looks OK.

Is it possible for condensation to cause this appearance and can we just ventilate and let it dry out or should we be looking for other sources of moisture?

Ooo, damp, my favourite subject. I think we've got every type in our (apparently) 1930s yet solid walled limestone house. I like the plastic on the wall idea to help ascertain the lurch of the damp. Good tip!

Lurch? Source!

We have very similar on the chimney breast in our dining room. Been there for years, not got bigger or smaller. A stove fitter had in for something else in the front room saw the dining room and reckoned we should put an air brick in the chimney breast to get better ventilation. We haven't bothered to be honest.

We're in a victorian house with no cavity wall. The chimney breast in the bedroom above it is fine. Although a different external wall in the bedroom has a similar patch.

Our house is bad for condensation. We have a dehumidifier running 24/7, don't dry washing inside, try to open windows as much as possible. Apart from fitting a positive ventilation system I don't know what else to do. Our damp patches remain in the summer.

Have added a picture, it looks like a poodle head!

Oh and a small section of our external living room wall is only single brick rather than double brick. The wall there can sometimes be wet to the touch inside. Living room is the worst for condensation, we wipe the windows dry every morning. Curtains are mouldy in patches! Grim.

I read that you get condensation in the actual chimney when you haven't got a fire in but that air bricks don't really help as you don't get the draw up the chimney.
Since we're sharing, here's our most recent patch. There has been a LOT of rain but we recently had the render knocked off and the pointing redone so it shouldn't be that. Our chimney situation is a little odd, we have a fire place and what appears to be a chimney going up inside the solid wall (so no chimney breast as such) but no stack on top (you can see where the chimney was because the tiles are different on the roof). I'm currently thinking that those tiles are leaking or this is a something to do with condensation forming in the chimney. Or our pointing is crap or our stones are broken. Or something else.

a chimney which is not open top and bottom will get condensation starting on the inside and soaking through to the room plaster. The stain will often be yellow or brown as it carries tarry material from the soot. This stain will persist even after you cure the damp.

Water vapour is lighter than air, so if the chimney is ventilated top and bottom (it need not be a huge hole) there will be a current and the water vapour will rise out. Each chimney usually has (at least) two flues in it, one from the upstairs and one from the downstairs fireplace. Both flues need to be ventilated.

If your stack has been taken down from the top and roofed over, you should be able to see the open flues in the loft.

PigletJohn, if we put an air brick in the chimney breast should it be on the outside wall. Stove fitter seemed to infer it should be inside, so a hole into my dining room. I was too busy stressing over the stove to quiz him on this but that doesn't sound right.

Oh and once I put an air brick in, if you say the stain will persist do you mean I can never get rid?? Or do you mean I will need to repaint? Thanks.

Oh and this is the bedroom stain, external wall but not the chimney wall. Gutter seems ok above, not running over. No drain/down pipe near this part of the wall. House was re roofed a couple of years ago.

So no idea what's going on.

Both stains interestingly enough only appeared after painting the rooms. Lived in the house 12 years, no damp patch. Painted the dining room and patch appeared within weeks. Two years later painted the bedroom and again patch appeared a few weeks later. Both rooms had just been paint before, not wallpaper.

inside. You can put a plastic grille over the hole and paint it to match the wall, or use a brass one if you want. If you do it during building works you can sometimes ventilate the flue under the floor.

Strip off the paint or paper from the stain and apply stain block before redecorating.

Thanks PigletJohn

I spent last night reading about damp. I need to re-arrange DDs room to move furniture from external wall side of room. Have been thinking about this anyway, but good to know it should help!

Update: the plastic bags are dry on both sides- been there about 24 hours. However, I have had the heating on low, not dried any washing and also aired upstairs in the same period and there was markedly less condensation on the window. Am going to keep monitoring and start with clearing out and moving furniture!

So glad this thread was started, I feel less like this is a problem to be ashamed of (although I know I should have addressed before now...)

My plastic bag was wet on the outside, yet the patch had got bigger and darker over night. Weird.

We've had these mysterious patches on the upper part of a bedroom wall for 4-5 years now - started noticing them after we removed the wallpaper, re-plastered and painted the walls. They've stayed more or less the same, sometimes fading slightly. The damp meter always showed high humidity there. Even a hairdryer wouldn't get rid of them completely - just make them fade a little and they would be back to the same saturation within hours. It's an external wall and the pointing, the roof and gutters were checked carefully - they are all in top shape. Internal leaks were also excluded because our combi boiler never lost pressure. Then yesterday, after reading about hygroscopic salts contamination, I 'tasted' the patches with a wet finger:). The taste was more bitter than salty and definitely very different from how the rest of the wall 'tasted'. So I had the idea to wash the patches with some warm water and a sponge. I dried with a hairdryer immediately and repeated several more times, until the patches were gone completely (alas, together with some of the paint but I have some left for touch ups)! They haven't yet re-appeared but I have the sneaky feeling they will do eventually, especially after reading this: www.davidkinsey.co.uk/pages/the-effect-of-salts.php.
So for anyone with a similar problem, maybe try curing the damp by soaking it and see what happens:). Might be a temporary solution but at least you'll know the cause of the problem.

Before and after photos

@WhoTheFuckIsSimon

Just wanted to make a comment on how early you put up your Christmas decorations!

If anyone is reading this is wrong it is 150mm from ground level. That is what is written in the building regulation.

You're right, that is the current minimum height permitted.