Cracks, plaster skim and paint

6 Jan 2006
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United Kingdom
I have had a number of walls and ceilings skimmed over the past 2 years. The skim has covered old plaster that was past its best, plenty of lumps, bumps and cracks. In some areas plasterboard has been used then skimmed. My question is about cracks appearing in the new plaster. The cracks are at max 1-2mm most are hairline. I have read a few posts on this but wanted to confirm a few things.

1. I have some walls that have hairline cracks and others that have none. I know that temp affects the plaster (expansion and contraction) but I have one wall in the kitchen that when the temp drops in the evening and the radiator has gone off the cracks appear and when the room warms up they disappear. I can't even find them. Would you do anything about this? Maybe fill the cracks when the temp drops or just leave well alone.

2. The landing ceiling was one of the first areas skimmed. In a moment of madness I decided to change the matt emulsion paint I had used for a mist coat on other walls and ceilings. The first coat on the landing ceiling I would not call a mist coat, the paint was too thick. The finish looks ok but quite a few cracks have appeared on the freeze area of the ceiling above door frames and in particular where the freeze joins the main ceiling. Do you think this has something to do with the paint? I am convinced some of the cracks are not the plaster but the paint lifting from the surface and cracking or separating.

3. I have a few cracks around door frames on the freeze of the ceiling, these are at various angles, some more eratic than others. I know door and window areas are weak points but is this something to be concerned about. Is there a simple way to fill the cracks without raking them out. I don't want my ceiling to have lots of obvious areas that you can tell have been repaired.


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The walls are mainly brick, the odd one is lathe. The ceilings are lathe. The house was built mid 1920s.
Of the worst cracked walls, is it the lathe is worst or brick with cracks ? Also, is the worst of the cracks near or next to heating ?
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The kitchen wall that looks bad when the temp drops is brick but the radiator is on that wall.

The other walls with hairline cracks are brick with no rad on the wall but there is CH in each room.
Sorry for loads of questions but what Exact name and Brand was the emulsion you used as an first coat over the new plaster ?
I started in some rooms using, dare I say it, b&q value matt white. It's thin already but I thinned a little more for a mist coat - 2 coats followed by 2 coats of Crown matt (natural collection). The finish looks good.

I have recently taken advice from here and used dulux trade that I found a lot easier to use and the coverage is a lot better (less coats).

The landing ceiling I made a gaff. I used Crown Matt White for my mist coat. I think it was too thick and I stupidly didn't thin down.
First of all let me explain that applying New Plaster over already damaged old plaster is known as a quick cheap fix. It looks great at first but give it 6 months to 2 years then problems with the old surface start to creep through to the New Plaster. i.e. Hairline Cracks start to re-appear. I know it is down to cost but thats why people take the cheaper route then later regret it a few years down the line. What should have been done is rip out all Old Plaster and re-plaster onto brick walls and sheeted with New Gyproc on old lathe. That way you would have eliminated the Old Plaster problems. Though this route is dearer ofcoarse. However, if the emulsion is the problem (which i doubt) then this can be worked out by investigating the surfaces in question and seeing if in actual fact it is the paint that is creating the hairline cracks. Therefore, any chance of pics ?
I think Third_Eye has most likely got it bang on.

I had most of my house re-skimmed last summer and have the same situation with hairline cracks creeping back in, particularly so in the walls that were the worst before the skim.

I'm in the process of painting again at the moment and I'm using Dulux ColourFlex Rich Matt which claims to be able to keep such things covered.

It's to early to say how successful it will be but with one coat on so far I'm not going to be betting the farm on it. It's strange paint - it seems to skin in a similar way to the Kitchen and Bathroom stuff, a trait which I'm sure means none of the pro's here like it. If you do try and use it work quickly, otherwise when you roller it will lift where you've cut in.

I honestly wish, as Third_Eye said, that I'd had it stripped back to brick and re-bonded, then finished - or even had some thermalboard put up and skimmed over as that would have helped with the heat retention of my solid walls.
I feel justified in planning my St Paddys weekend around my hammer and bolster to remove all plaster before installing a toilet in the cloakroom!!

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