Paint bubbling weeks later

25 Apr 2010
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United Kingdom
Hi there

My first post. I have read these forums with interest and seen various related topics, but thought I would ask for advice on my specific problem.

A few months back a came to decorate our spare bedroom - upon stripping the wallpaper I noticed that under humid conditions the original paint underneath was bubbling. I left the steamer on for an hour and popped/scraped as many of the bubbles as possible.

Where the bubbles were removed I had to use filler to get an even surface (otherwise I would have to strip the paint off the entire walls which would take weeks and weeks).

Painted the entire room and, surprisingly, 98% of it is fine. However, a day after paitning on one wall a small bubble appeared. I scraped this back, filled it, primed and re-painted the wall. This bubble didn't re-appear, but a few days later a cluster of tiny bubbles appeared further up the wall. It gave the impression that each time I painted, a new set of bubbles appeared as a result.

However, I left them, and over the course of a few weeks this cluster grew bigger, and then a couple of months later a new cluster of bubbles appeared a few inches across from the original set. A few more weeks and a third set appeared in-between the other two sets of bubbles. They start as tiny 1mm bubbles in a cluster and later start to join together.

It would seem that the bubbles appear of their own accord (not just when I give the wall another coat of paint) and they can take weeks to form. I don't know if this is a fault with the original coat of paint, a fault with my paint, a problem where I have used filler or a problem with the original plaster. Although the whole room bubbled when I first stripped the wallpaper it's now only one wall that is affected and this is confined to an area of around 2 feet.

For your information, after sanding and cleaning the walls I used a coat of white matt emulsion, and then a coat of magnolia Dulux Trade Diamond Egg Shell.

Anyway, I have scraped the bubbles away and half seem to go down to my first coat of paint over a layer of filler which is well attached to the wall, the other half did the same but caused the filler to fall away down to the plaster. The area is now somewhat uneven.

What I intend to do is sand the area as evenly as possible and then apply either an oil based undercoat or damp sealer. I'll then paint that patch with white matt emulsion and finally go over the entire wall with the Dulux magnolia.

Does this seem like a resonable thing to do? If I need to fill again to get an even finish, is there any particular filler that is more suitable (I used quick drying filler out of a tube from Wilko)? Also, should the sealer go on first and then the filler, or the other way around?

I have just enough of the Dulux paint left to do this one wall and it's quite expensive, so I've got to try and get it right this time!

Any advice appreciated! Thanks,
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Outside chance that it could a compatability problem with the diamond matt..that stuff can be

Otherwise it sounds like you on the right course..scrape back the worst..and more, then seal with oil based undercoat..knoting, (if its a small area or Zinseer bin primer..

Then fill..I wouldnt use the ready mixed stuff...stick to polyfilla or something you mix yourself (tetrion isnt much good though for face filling)

you didnt say whether the affected walls are exterior or its a bedroom I assume its upstairs?..unless you live in a bungalow of course..

Unless its only happening on the cold exterior wall there should be no reason why its caused by I wouldnt bother with damp sealer..and damp sealer is only really any good if you stop the source.

If your finish coat has a sheen and you do a lot of filling you might find you will see 'scars' where the filler has been...matt might be a better alternative.

If the problem persists..and it isnt down to damp in the wall I would suggest repairing the bubbles again, giving the whole wall a couple of coats of oul based undercoat...leave it dry for a few days, give it a rub down to get rid of any nibs and give you a key...then line it using 1000 grade paper and ready mixed paste..

Hope that helps a bit..

Stick around, some of the other regulars on here may offer some more advice..
Many thanks for your reply, really appreciate it.

I got some damp sealer prior to your reply, but it's oil based and says it can be used as a primer, undercoat or even a top coat, so I am guessing this will do the trick.

It's an interior wall, with a bathroom next door.

So I'm right in thinking I should seal first and then fill, not the other way around? The thing that concerns me is I'm trying to fill a recess that's only 2-3mm deep and several inches wide, and I'm worried about the filler not taking properly. Is it more likely to stick to the wall if I fill first and then seal it after?

Many thanks,
It would stick to an undercoat of emulsion ok...not sure about a damp wont hurt to try though..

The reason its betterto seal first is the damp can get to the filler (which is water based) first..if the sealer is there the damp (if it is damp) wont affect the filer

Is the problem only on the outside wall then? or maybe low down where the wall backs on to the bathroom wall?
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The problem is about 2 feet up from the ground. It's an upstairs bedroom and the bathroom is the other side of the wall.

Since the entire room has been such a pain in the back side, I suspect it isn't damp but is something else (I was just being over precatious with the damp sealer because 4 months on I'm fed up of the damn room!)

I'm really hoping I don't have to fill, because I think this is adding to the problem. I've scraped the loose paint and filler away with a razor and then gone over the whole area with a sanding block. Now I've primed it, and the area isn't totally level. I'm hoping to be able to build up the layers of paint to level it out but this might be wishful thinking?
2 feet up?...there woldnt be a bath on the otherside of the wall wit a bit of dodgy silicone sealing the rim of it by any chance would there?
Yes there is a bath the other side of the wall!

The silicone has started to go mouldy again and needs re-doing soon. Do you really think the water could be getting down the side of the bath and having an effect on the other side of the wall? :eek:

EDIT: I just measured, and the affected area is alongside the bath, albeit around 7 inches higher than the bath.
Could well be...

Lets go back to the bubbles it the top coat lifting and leaving the other stuff intact?..or are all layers of paint bubbling?
Hard to tell - some of the bubbles peeled off just the top coat, others seemed to take all layers of paint with them along with a layer of filler.

I've removed the sealant around the bath, and by the side of the bath (around 7 inches lower than where the bubbles are) it's very mouldy and wet. In fact, down the side of the bath it is packed with silicone, tissue paper, expanding foam and grout (the guy who lived here before claimed to be a tradesman but was a total cowboy).

I removed the tiles just above the bath and the plaster behind them is damp although not soaking. I believe it's breeze block behind the plaster.
Well it turns out it was the bath leaking. I removed the tiles and stopped using the shower and no bubbles have returned (although I now need to repaint the wall yet again).

Anyway the reason I haven't been back sooner is because I've spent the last few weeks having the bathroom completely re-done, with Aquapanel behind the tiles and the bath fitted properly, etc.

Call me psychic

I would post more on here if it wasnt for the idle gits who cant be bothered thanking people.. you doing mate?

Call me psychic

I would post more on here if it wasnt for the idle gits who cant be bothered thanking people.. you doing mate?

I'm fine thanks Zamp', how's yourself? good to see ya here again mucca. ;)

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