Condensation or ingress?

project_c

Trying to work out why I'm getting dark patches on my kitchen wall. Patches appear high up on top right side of back wall and also over on the party wall in the same area, near the top, towards the corner. Victorian terrace, upstairs maisonette, no damp anywhere else in the flat, generally quite well ventilated, chimneys aren't blocked. The kitchen is an extension (built many decades ago) with a flat roof. Had flat roof and parapet checked (by several different companies to make sure we weren't getting ripped off), had it repaired where there were any potential issues, didn't solve issue. Painted over the patches once to make sure it wasn't just some old stains, patches came back over the course of a couple of months. Patches seem to come and go regardless of rain but possibly more present when we're cooking (we use an extractor fan and open windows when we cook, but hasn't solved the problem). The back wall is pebble dashed and the dash is pretty old, but I don't think it's trapping or letting in any water, so I'm guessing this is most likely condensation, especially as patches also appear on party wall and not just back wall, but is there any way of telling the difference between water coming in from outside, and condensation for sure?

If it is indeed condensation I can look into installing ventilation up there, but I don't want to waste money if the problem lies elsewhere. I would happily let an expert look at it, but my experience with surveyors and 'damp experts' has not been great so far and I have no idea where to find an actual reliable expert who can figure this out, so I'm open to suggestions for that too. Thanks!

neilmcl

We'd need to see some pics, both inside and out to give any sort of definitive comments.

tacpot12

I really don't know whether this will work, but as it should be cheap to try I will suggest it: if you get a small pot of enamel paint (such as modellers use), and paint a square about 100mm x 100mm on the wall where the damp appears, if the water is coming from condensation, you will see water on the painted patch, if it coming from outside you won't - the paint is waterproof. To avoid any drips from the section above the patch, you could run a bead of silicone at 45 degrees down the wall, and paint up to the underside of the bead - water above the patch will run down the silicone, avoiding the patch. 

If you try this, and it works, please can you let us know back here as others may benefit. 

Rural_Puppy

You could try increasing the temperature of the wall by putting up insulating wall paper with the appropriate adhesive. That might help reduce the condensation level?

greatcrested

blocked /overflowing gutter outside or leaking downpipe?