Water mark

[Lf3928]

Can anyone shed any light on this water mark? It appears when we have had heavy rain or its cold out, it is always the same shape never grows etc. It will disappear when it warms up or the heating is on or a fires been lit. It is an exterior wall and the other side is the neighbours porch. We've recently had the roof and guttering repaired and the house had a damp proof course up to 1metre a few years before we bought the house. The patch has only been seen Since the wallpaper was stripped (it was textured cream paper before). Thanks in advance.

 

[JohnD]

if you suspect condensation, tape a piece of clear plastic tightly over it. See if water forms on the room side (condensation) or on the wall side (wet wall)

Post a photo with your hand or a coin on the patch to show scale and which way is up. Stand back and show the patch and the whole wall floor to ceiling. Also a photo of the outside showing the porch roof, gutter, downpipe and wall, and where the wet patch is. I suspect rainfall from the porch may be running down.

How old is your house and does it have cavity walls.

 

[Lf3928]

Thanks John!

Ok so here's some pictures. I can't quite get floor to ceiling as its too high! He mark starts about 1.5 metres from the floor. From the outside the mark is in line with the guttering bracket but on that wall inside the neighbours porch. As you can see the houses are old 1893 I believe so that wall is solid brick.

 

[Lf3928]

Can only add one pic per post for some reason.

 

[Lf3928]

Outside

 

[scruffybiker]

Hi. I get exactly the same thing in my house. Same age as yours & solid walls. Its hygroscopic salts in the plaster in my case. The salts suck moisture in and it appears damp. But to the touch its just cold. Search salt damp on google. I also have a chimney that suffers from it due to salts. Gypsum plaster doesnt help either especially on solid walls in old ptoperties where they need to breath. So if you can rule out a leak then it'll be salts. You could also confirm this by buying/hiring a humidifier. When using humidifier the salt patches will become very noticible. Hope this helps..

 

[Lf3928]

Thanks so much! It's exactly as you describe it, cold but not wet. From googling it does sound sound like salts as we have a smaller patch on an interior wall and it our bedroom. Both rooms are the only ones to very old plaster. I'm assuming replastering solve this then?

 

[^woody^]

Salts would tend to leave salt stains.

That defective render and faulty gutter end are certainly a more likely cause than condensation.

 

[adrian.groves]

I had a similar problem in an old house which had a new chemical damp proof course but not been replastered. The old damp had caused the salts to appear in the plaster and they attracted the moisture in the air.

I was told to scrub them with a vinegar solution which sounded as though he was taking the mick but I did and it worked.