Damp spot in new plaster. How to manage

[Sef1928172]

Hi all. Looking for advice in how to handle a damp spot in new plaster skim. Solid brick walls

This spot has not fully dried out. When it rains or is humid in the room, the patch gets bigger (second pic). There is no external indication of water being able to get in here but previously there looks to have been some holes filled in with filler internally that correspond almost exactly to where this spot is, so I wonder if that has something to do with it.

Do I need to hack off plaster and see what is going on below? If it is old filler having an effect here, what would I need to replace it with?

Alternatively, is there a type of paint that is can use that will be able to hide this? I have read that one can apply salt neutraliser to stop efflorescence then paint. Is that correct?

Many thanks for any help.

 

[Wayners]

Get a summer fan blowing on it. Not heat just air movement.
Should see a difference in a day. If it don't go or comes back you know it needs looking at.

 

[Sef1928172]

Thanks. Sorry. Should have said that I have had a crack at that already. That first pic is about as small as the spot has gotten after a good few weeks of warm weather and dehumidifiers and also put a hair dryer in it for a while.

So is hacking out plaster down to the brick the only option then?

 

[foxhole]

External pics required.

 

[robinbanks]

Solid brick walls

Uninsulated? Oof, do it right and convert it to being the external skin with insulation and an internal skin

 

[Sef1928172]

Here is a pic of the external. I’ve circled about where the internal patches are The new render there lines up with the white paint in the other pic so that doesn’t match up as being the cause I don’t think.

@robinbanks: do you mean building an internal stud wall and insulating between?


Thanks

 

[foxhole]

Has external wall recently been rendered ?

 

[Sef1928172]

the render where the damp is is old render.

There is newer render at the end where the wall was extended to make flush with ground floor

 

[robinbanks]

If extending that metre(?) caused a change to more than 25% of the thermal envelope it should have been done under BC and I'd be amazed that they would let work pass that had no insulation.

I'm actually amazed in this day and age of gas prices the way they are that people want to live in houses with uninsulated anything!

 

[Sef1928172]

Thanks robinbanks

To get back to the original question, is there any type of paint that can be used to cover this or will it be necessary to hack out that section where the damp is and see what is underneath?

Thanks

 

[securespark]

On the external shot, there seems to be damage or gaps at the top of the render below the fascia board.

Could water be getting in there and making its way down the wall? Or where the new render meets the old?

 

[Sef1928172]

I see what you mean. I guess I’ll have to look into that and possibly replace the fascia board.

With regard to the wall in the short term, I take it it the options are just paint over it and see how it goes (anticipating that it will peel off eventually), or hack back plaster and let it dry out. Does that sound about right?

Thanks all for your input