Damp patches on wall

[dybleah]

Hi all,

I have a Victorian era terrace house with some damp patches that have come up in the last 2 years, mild initially. Now the wall destruction seems to be accelerating, causing rising flakiness! The outside aspect of this bit of wall doesn't get wet (it is sheltered). I've read a bit about damp and the causes. Particularly about the controversies around the existence/treatments for rising damp. For if this isn't it, then what could it be!?

I'm suspecting that the plaster on the walls are gypsum, given that some of it looks pinkish underneath. This would mean that it is relatively non-breathable and thus may trap moisture in the solid walls. I can't see any leaks anywhere, nor excessive moisture on the nearby windows. No gutters spill down that area.

So would my first step be to replace the plastering in that area with a 'breathable' plaster? Any recommendations on what products are best?

Thanks for opinions!

 

[bobasd]

soot/chemical reactions in the chimney breast flue might be a major cause of your difficulties?
there are signs that the area has been worked on in the not too distant past. do you know anything about previous work?

can you step back, clear any furniture, and pic the whole chimney breast?
and pic the back wall of the c/breast from outside?

is there a fireplace open or blocked in the room above?

 

[dybleah]

Thanks for your reply.

I'm sure there has been work to it, but can't be sure what and when. We haven't done any work to it since moving in 10 yrs ago. There were some marks around the bottom of the wall when we moved in, but very very minor. Then over the course of the following 7yrs, it slowly came up around a foot from the skirting. Then in last 2 yrs (incidentally when we shut off the radiator on that side of the wall...?cause/effect), it has accelerated to go up the wall another 2-3 feet.

It is not near the chimney breast. It is actually part of the front of the house. Included photo to show you where it is on the inside and out. Thanks again!!

 

[bobasd]

so much for me jumping the gun - thank you for correcting me.

the previous work might have been remedial damp work, done just prior to selling the property?
the headers in the wall suggest that its a solid wall.
the external sand and cement plinth suggests that the plinth might have been installed in an attempt to combat previous damp?
the plinth should be cut off from contact with the ground - by about 40mm - 50mm.
there's an air brick that seems to be set too high for venting the suspended floor - i assume that you have suspended floors?

i'm surprised that you dont report further damp signs in the hall, and below that (bay?) window?

it looks like rising damp so IMO: the best remedy is to remove the skirtings, & knock off the plaster back to brick, to about 300mm beyond any damp signs.
then render with a 4:1 or 3:1 mix of sand & lime, skimmed with Limelite finish.
if you have a metal corner bead and its rusting then saw it off above the rust, and replace with a plastic bead.

have you ever been under the floor & inspected your joists for rot or excess condensation?
do you have air bricks venting at the front & rear elevations?
the original step would probably have had a vent grill below the nosing - but the new tile step will have blocked that ventilation for the hallway sub-area.

doing the above will give you quite a few years of damp clear decorated surfaces - it will not remove or "cure" any kind of damp. it will merely mask the damp.

 

[dybleah]

Thanks for the detailed reply.

There may very well be remedial work to this solid wall as you say.
I wouldn't be surprised if there were damp issues in the past.
The air brick does seem too high... I think the floors are suspended, yes.

There is some damp on the wall opposite, but we had identified a non-intact gutter pipe that was fixed. There is no damp in the hallway / under window areas surprisingly.

Never had the under floor / joists inspected. We aim to get a dehumidifier in the house after this.
We have air bricks at the front and back (built into the 2 steps leading into the garden)
And yes, that's a good point about the vent grill and tile blocking it. I note that some houses down the road have this vent retained.


From a works perspective, I aim to just do that section of the wall.
Do I need SBR or PVA as a base layer?
Also, can I just use the 3 step thing as Limelite details in the below photo (no plugging of any products intended)?

Thanks so much again!