I've spent the last two or three weekends slowly painting the walls of my bedroom and was planning to wake up today ready to give myself a big pat on the back and continue with the next stage (skirting, varnishing, carpeting etc). But on close examination discovered the latest coat had started mud cracking and I've no idea why.

Now I'm expecting all sorts of questions about every detail of the processes I went through so let's see if I can pre-empt all of them:

The walls started off as bare plaster after I had the room completely replastered...ahem...two years ago (I'm not the quickest at getting round to DIY).
First I covered the walls in B&Q plaster sealer (couple of weeks ago)
Then I painted the walls in B&Q base coat (Saturday morning, last weekend). Walls were fine after that, smooth all over.
Then one coat of Dulux matt emulsion (Sunday afternoon, last weekend). Walls were smooth all over after that but more coats were clearly required.
Second coat of same Dulux matt emulsion on Friday afternoon of this weekend. There was some mud cracking in the corners where I'd obviously over applied with a brush. I wasn't convinced the rest of the walls were finished either so I decided on a third coat, hoping that at the same time I could paint over, and hide forever, the mud cracking in the corners.
Third coat put on Saturday afternoon. Today, it looks great until you stand up close to it. The paint isn't mud cracked on 100% of the wall but it's at least half of it.

Now I didn't do anything different on that third coat, didn't apply it any thicker than the first two, so I can only think that the second coat - although I'd left it 24 hours - hadn't dried out thoroughly. Very frustrating that it's happened in the first place, but more frustrating that I don't know why so I can prevent it happening again in future.

Anyway, now I need to know what to do to get rid of it. I've read several posts, all with different suggestions, but with no definite solution. It does sound like I'm going to have to sand it all down by hand, I've concluded that much, but then do I want to rub it down with sugar soap, apply a soft sheen, apply a new undercoat, use PVA....which ???

Does anyone have any actual experience of a tried and tested method for getting rid ??? Much appreciated.

DD

It's caused by the paint going on too thick.....nothing more than that. If it went on too thick at coat 2 it might have skinned on the top and then not cured properly at coat 2 and then with coat 3 it dried quickly shrinking and tearing the coat beneath - that's basically how I make a crackleure paint finish happen

Sand, fill if the texure hasn't disappeared, prime filled areas and repaint. Not PVA that's a glue, not sugar soap..that's for cleaning. Soft sheen if that's the paint you like but not otherwise.

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I would personally (depending on depth and extent of mud cracking) undercoat first.
Most of the time filling isnt needed.

Might save you some time and effort!

If you have to fill afterwards unlucky, lol

I can't understand how I managed to apply the paint too thickly on half of the room if I was using a roller with no different a technique than I used anywhere else. The corners, yes, because that's where I used a brush, but either way I certainly get the impression coat 2 hadn't dried out properly. Perhaps I should give Dulux a bell. Anyway, what's done is done - I need to fix it.

I think I'll start by picking one part of the wall and do one patch that I sand down and apply undercoat to and the other I'll test with undercoat with no sanding. Then I'll commit myself to one or the other. If I can get away with not sanding - brilliant, sanding with a sander - okay, light sanding by hand - nightmare. I promise I'll do whichever is necessary.

Thanks for your advice fellas.

DD

if the 2nd coat didn't dry...that would definitely do the same thing...but I am confused that it wouldn't dry. Do you have a damp problem? Did you turn on all the heaters and close the windows or was it a hugely wet day..did you wash carpets at the same time. High High humidity is normally the cause of an emulsion not drying.

BTW..."fellas"....harumph

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Skilled Artisans are not cheap....Cheap artisans are not skilled.
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Oops, beg your pardon.

Room's not damp, windows were closed and the room is bathed in sunlight so I didn't turn the heating on because it was a nice day Saturday and Sunday and clean the carpets ??? The room is a bomb site so no cleaning planned and the thread bare piece of tat that is my carpet will definitely be geting replaced once I'm done.

I thought your previous answer implied that the second coat hadn't dried right through and that was my initial reaction so perhaps I got the wrong end of the stick. Either way, like I said, it doesn't matter what caused it (although not knowing is irritating) but it does matter what I do to fix it.

If I get home before it gets dark any day this week I'll have a go, otherwise it'll have to wait until next weekend.

Thank you young lady.

DD

1. B&Q plaster sealer.

2. B&Q basecoat .

3. Dulux Rich matt.

I think your problem is between the B&Q basecoat and the Dulux rich matt. There is no need to put B&Q basecoat on as you have already put plaster sealer on the walls.

Dulux rich matt is not a Trade quality paint and can be the cause of all sorts of problems. Painting over B&Q basecoat, is one of them.

My thoughts exactly...incompatability between the paints somewhere along the line...add rich matt into the equation and youve got a right ol cock tail on your hands...you didnt need all that stuff on the wall...a thinned coat of ordinary vinyl matt would have been fine...light rub down and then another couple of coats...slightly thinned too..

Failing that id opt for the other 'fellas' suggestion of the paint being put on too thick..

I cant see hw it can be anything other than one of these...

Is the b and q plaster sealer oil based?

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I'm thinking the culprit might be the plaster sealer! When you applied it did you check afterwards if there were any thick patches where it hadn't penetrated hence leaving it sitting thick on the wall. If there was then when you started applying the basecoat you have painted over the top of it causing your cracking effect! If not did you use silk or even vinyl matt emulsion as your basecoat. If you did this will also cause the undesired effect. You do not need a plaster sealer for new plaster, just a thinned down coat of contract/flat emulsion followed by your 2 coats of preffered colour emulsion.