Troublesome spot keeps reappearing

[atsgmo]

I wonder if I can ask for your collective expertise

We have a strange spot on on this wall which keeps reappearing , despite my best efforts with Zissner Peelstop to solve it.

As you can see from the photos, this room is the lowest part of the house and behind the brick wall is a void under the stairs. The paint has always peeled/bubbled in this spot, and when we redecorated (covering the lovely l*m*-g***n paint you can see in the photo) we tried to resolve it with Zissner Peelspot. But as you can see the patch keeps reappearing and getting slightly bigger. The centre is slightly damp to the touch and the paint is powdery on the finger. When I have sanded it away you can see what the plaster underneath looks like - there is a clear darker spot in the centre.

The only other possible clue is that you can just make out a slight cracked line (length about 60cm) in the plaster running horizontally through the spot - which has always been there.

There are no other problem areas in the room and damp is not an issue. It is just happening in this one isolated spot. On the other side of the wall is a void underneath the hallway floor, where the stairs are)


Does anyone know what might be causing and is there a permanent fix?

thanks

 

[bobski]

Looks like grease or oil.

Waste of time with peelstop.


Zinsser B - I - N would fix it for you.

Spray or can.

 

[Monkey Boy]

Get under there and find leak

 

[atsgmo]

Unfortunately it is impossible to get behind that wall without making a hole. Behind that brick wall is a void underneath the hallway flooring.

 

[Monkey Boy]

Unfortunately it is impossible to get behind that wall…

 

[Steve Brown]

Looks like a bridging problem. Room looks like a split level house, you can see a moisture line.
Remove skirting and I bet plaster down to floor, I'd personally knock off plaster back to brickwork a foot above that stain, float and plaster with Renderlite system (having a bridging gap).
If that floor void on opposite side of room is above lower room level then you will have to apply K11 tanking before you float and plaster.

 

[atsgmo]

Thank you. Yes the room is split and the void behind teh wall is above the lower room level. So this could be a possibility. This is very helpful

 

[Danny]

I woud use that stain block https://amzn.to/4peG1g7

Then fill but past the mark then sand and paint and fill out again if it needs it...

 

[atsgmo]

Thank you. Please excuse My ignorance but what do you mean by fill? Do you mean that I should just dig out the hole and fill with poly filler? Or as the poster above suggests replaster that section?

 

[Danny]

Thank you. Please excuse My ignorance but what do you mean by fill? Do you mean that I should just dig out the hole and fill with poly filler? Or as the poster above suggests replaster that section?

err fill the area out and then sand it to blend it in

 

[Danny]

I would use easi fill and not poly filler... Poly filler is usually harder than granite to sand and so it makes an easy job of blending a dog of a job

(I have loads of experience with filler .... just getting that in before @essexandy of the others get in)

 

[essexandy]

I would use easi fill and not poly filler... Poly filler is usually harder than granite to sand and so it makes an easy job of blending a dog of a job

(I have loads of experience with filler .... just getting that in before @essexandy of the others get in)

Which brand of belt sander do you find lasts the longest mate?
I reckon you and @John j are the only people to have used and burnt out every brand.

 

[Danny]

Which brand of belt sander do you find lasts the longest mate?
I reckon you and @John j are the only people to have used and burnt out every brand.

Well... Titan from B&Q seem to best value and come with a 3 year warranty