Damp - condensation or some other cause?

[Damp1979]

Hello - looking for some help. House built in 1979. Lived in for about 16 years. End of last winter I noticed marks on a wall which looked like water had run down it. On another day I could see water droplets actually running down and surrounding walls felt damp. I also get some mould occurring around the window frames.

today, the walls feel wet to the touch. Can anyone help? PigletJohn? I’ve tried to summarise some key facts and have attached a photo and diagram.

• second floor bedroom
• three external walls and two windows double glazed
• one radiator (large, output meant to meet room size)
• house built 1979
• no external damage to brickwork or guttering - external wall is dry to touch
• room is not used for drying washing
• windows opened every day but no trickle vent
• two people sleeping in the room
• walls on first floor appear dry

any advice please? Thanks

I think you need to @ someone of you want them to see your post btw.

Can you see on the roof? Cracked or missing tiles? Even if it’s further up on the roof than where it meets the wall. Water will always find a route and it can be tricky working out where it’s getting in, but if there’s no damage to the external wall, roof tiles would be my guess. Is there/Can you get in to the loft space? If so you might be able to see if there’s any water trickling down.

Thanks @Judashascomeintosomemoney i tried to @ Piglet but I can’t see the name come up?

there’s no damage to roof tiles and the moisture seems to start at the midpoint of the wall, not ceiling. there is supposedly cavity wall insulation but that job was done way before we moved in. Can it break down? Could that be a cause?

@PigletJohn any advice if you get a moment

@Judashascomeintosomemoney got it to work eventually :-)

Condensation is cured by ventilation.

Leave the window open all day, and do not drape wet washing indoors.

Stand back and take pics of the entire wall, floor to ceiling, preferably unobstructed. Also of the outside wall, including roof, gutter and downpipes.

Tape clear plastic or clingfilm tightly to the wall. If it is condensation, water will form on the outside. If the wall is wet, water will form under the plastic.

Thanks @PigletJohn ive just put the heating on and popped a couple of extra heaters in the room to try and dry it out. I’ve also wiped the walls so there is nothing to see on a photo - sorry did this before I read you advice. I guess if I can dry the surface water a bit the plastic test
might work better. I will let you know how I get on.

Have you installed new windows lately?

@Palmasailor no new windows recently - changed them about 13 years ago.

I’m pumping the room full of heat at the moment with the windows open. Walls are
drying out. I’ve pulled out bedside cabinets and looked behind the bed head board and it is dry behind there but not where the plasterwork is open to the air. Wondering if that points to condensation too?

Ventilation takes damp away, not heat.

You can set a domestic fan (not a fan heater) to blow on the wall to evaporate water, but you also have to open a window to blow the water vapour out.

Cavity wall insulation can provide a water path along the wall ties, but seems like a lot of water if you can see it running. Is there a lot of rain when or before you see it? If it's been fine for years before, something has changed, roof damage, wall damage, gutters/downpipes leaking?

@plumtreebroke yes, a lot of rain and when it’s not been raining it’s incredibly humid outside.

I’ve dried the walls out with heat and two windows wide open: clung film is up. Let’s see.

No moisture on either side of the cling film today. A little on the windows which I removed with a Karcher. I will see how it goes.