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Painting & Decorating Question
Paint bubbles on surface and lifting plaster
I have repaired small recurring vertical cracks on 2no staircase walls and it appears by using denso tape it prevents the cracks coming back. This problem only seems to happen in cold winter months. I assume the wall brickwork/blockwork expands and contracts with the weather. I have used Tetrion all purpose filler to cover the denso tape and have rubbed down to a flat wall surface. The problem I have is with paint bubbles on the surface I have just rubbed down. If I use a very watered down coat it causes bubbles under the surface - they do dry eventually but if I use a thicker coat it just lifts the surface plaster off. I am using Dulux flat matt trade and find this paint extremely thick. I have left the filled surfaces to dry at least 48hrs before painting. Can someone please advise why this is happening.
Without seeing the problem this is almost impossible to solve, but it would seem that you have a damp issue. Water will always find its way through so you must find where it is coming from before you can deal with it. Gutter, roof, pipes....check them all. You can try good old PVA solution under your paint, but no coating will sort it if it IS an external damp problem. A good builder ought to find the reason for this. Sorry not to be more help.
Answered 4th May 2013
It sounds to me that if the paint keeps bubbling even though you have applied a mist coat that the previous coatings were not watered down on the first coat application so it will always bubble as paint can get in behind . Use a sharp edge scraper blade and take off the paint until you find a good edge that sticks then apply a mist coat. Rake the crack out properly into a v shape and use wall jointing filler . Apply one coat with a caulker let it dry then apply a second coat if applied correctly is easy to sand and will not grin through the paint.
Answered 17th Feb 2017