Paint flaking off and stains starting to appear...

[portuguesejohn]

Renovated a couple of rooms by having them stripped of old wallpaper and replastering/skimming (the plasterer fully replastered some areas, other areas just needed skimming), recently painted with a mist coat of emulsion followed by another coat.

On one of the rooms it didn't take long for some paint to start flaking off, as well some beige/yellowish stains to start coming through on the chimney breast and around...

I've attached a couple of pictures.
Pic #1 shows the paint flaking away
Pic #2 shows the whole issue area - The flash on the camera really highlights the problems!

Trying to understand what this could be, some possibilities:
* Some sort of infiltration that wasn't visible on the old wallpaper.
* "salts" seems to be a common thing talked about on the old web, especially since this is a chimney breast.
* Could the plaster not have dried properly? This room is north facing and the weather has been terrible this year.
* Incorrect painting of sorts? We are sort of new to DYI, both rooms have turned out great except for this area in the photo...

Would also like some recommendations on how to address this without being too "destructive". Just had the whole room redone, I need hacking away at the walls again like a bullet to the back of my head .

Could I try tackling this with a stainblock primer, let it dry and apply new coat of emulsion?

 

[terryplumb]

How long between plastering being done and painting commencing ?

 

[portuguesejohn]

The room in question was replastered around the 8th of January, mist coat went around the 9th of Feb and full coat about a week later on the 16th. We let it dry for a full month basically, lots of ventilation and a fan going, but yes, the room is north facing and quite cold without heating on.

Your question actually made me look at some old photos, including some that the plasterer sent me whilst doing the work! I can see the affected area taking a full replaster! Pic attached.

This area of the ceiling is angled, I believe my house has a "raised tie", where insulation could be poorer and prone to condensation issues.

 

[terryplumb]

Well I am no expert when it comes to painting ,and hopefully more knowledgeable members will contribute shortly ,but it appears to me to be a moisture / damp problem.

 

[portuguesejohn]

Attached I have highlighted an area that shows issues, before and after replaster and painting...

 

[terryplumb]

That just leads me to the same conclusion . What issues did you have before plastering in that area , moisture ingress from externally ?

 

[portuguesejohn]

That just leads me to the same conclusion . What issues did you have before plastering in that area , moisture ingress from externally ?

All the rooms used to have these wooden decorative strips, the actual name for these escapes me now, I have attached a picture from another room that had these as well.

The room in question also had these, and in the plastering photo you can see where we pulled them off - The red circle I highlighted had them and went all around the room. These things were a bastard to pull out, some of the nails were as long as my little finger!

 

[terryplumb]

Think it's called a picture rail.

 

[portuguesejohn]

Think it's called a picture rail.

That's it! Seems too coincidental that a lot of the problematic area is where this old picture rail used to sit in.

 

[portuguesejohn]

Another picture of the area that I found, after we removed the wallpaper and the picture rails, no obvious signs of water damage, unless someone here has another take?

 

[portuguesejohn]

Update on this: I have left a dehumidifier and fan going in this room for the last few days.

I also noticed the so called "salts/efflorescence" coming from that area where the paint was flaking. I have kept wiping the "salt" off and it now seems like no more is coming through!

I've been taking photos of the area every day to see how it develops with the fan/dehumidifier combo and it's starting to look much improved (attached).

Now, weather has improved in the last week or so, so I still have all of my various concerns:
* Is this going to get worse again as weather changes?
* Did this whole corner and chimney area just needed to dry out properly?
* If I wanted to repaint, what should my strategy be in terms of materials?

 

[portuguesejohn]

More updates on this… Total headache.

SO, after leaving it dry for weeks, months, through cold and hot weather (been very warm in the last week or so!) I thought now is the time to take a stab at this again, here is a video from yesterday that details what I had before doing any work: https://imgur.com/a/Z0y6DBi

I also had roofing work done in the house, the whole chimney stack was removed to stop any possible infiltrations!

So my plan was: Scrape the affected paint off, apply a coat of stain block primer (Crown) and repaint the next day - Attached (pic #1) you can find a picture after applying the stain block.

This turned out to be terrible. A few hours after applying the stain block, I noticed that in the bigger area where the plaster was exposed (beginning of the video), a tiny imperfection was attached to the wall... As soon as I carefully tried to remove it, the whole primer started coming out like a thin layer of plastic.

Arghhhh. Maybe it wasn't wise to apply stain blocker on stripped back plaster?? RIGHT. Strip it all back and start with a clean plaster surface. Scraped and sanding, clean it with worm water and sugar soap (pic #2 - The plaster looks wet due to the water and sugar soap).

Today I decided to apply a brand new mist coat, which you can see freshly applied in (pic #3), and also about 2 hours after application (pic #4).

I am starting to worry again about those darker patches in the plaster! It seems like the mist coat is not adhering properly, even though I was very careful to apply it! The plan is still to apply another layer of emulsion tomorrow and hope to be done with this issue - Surely by now the plaster has had time to completely dry!

Looking for advice on what should I do? Apply new emulsion coat(s) over the mist coat? Any other treatment beforehand?

 

[conny]

You need to wait until the plaster has fully dried out, (it usually turns pink in colour), otherwise you will trap any residual moisture behind the paint.
Best advice I can give is to scrape all the paint off, keep up the ventilation but also try to introduce some warmth into the room.
The warmth will draw the moisture to the surface and the ventilation/dehumidifier should extract it from the surrounding air. You don't have a bathroom/showwr room next to this room by any chance? Moisture from here could be exacerbating the problem.
You have to be patient in matters like this.