Can anyone tell me why Plaster cracks?

Question

I had a go at Plastering some of my Kitchen last night.
When i woke up this morning i noticed that the plaster has cracked in places.
Can anyone tell me why it has cracked?

Answer 1

did you dampen the wall before you plastered it? you also needed to make sure that it didn't dry out too fast, also do not put it on too thick, make sure that the plaster when mixed is at the right consistency....do not trowel out straight away as it forces the water out and that is another reason why it cracks.....you can level the plaster after about 20-30 minutes with a straight edge

Answer 2

Plaster Cracks

Answer 3

Plaster/gypsum is mixed with water (at least 50:50 so it's half water hanging off your walls). It takes some time depending on weather conditions to dry out - usually 2 to 3 days at this time of year - with the central heating on (though this is a bad idea as whenever possible plaster should be allowed to dry naturally- and banging up the central heating to dry your walls will get it to crack every time). Once plaster is applied - it should be revisited within 2 to 3 hours and worked in (setted) this smoothes over the surface and compresses the gypsum and forces out some of the deeper water (though water is usually splashed across the surface at this stage to reactivate the surface plaster). This is a critical stage and if ommited the plaster will definatley crack. Other tings that can cause cracking are - old plaster, poor mix, applied too thickly, insufficiently worked, wrong plaster - internal dividing walls and internal to external walls use different bonding mixes ...etc etc - just let someone else do it.....

Answer 4

Without knowing which plaster you have actually used it's not so easy to give a simple answer. Plasters have in general have different applications, the 3 most popular are, Brownning mainly used on high suction backgrounds like brickwork where old plaster has been removed etc. but before it's plastered the walls must be damped down with clean water, Then there is Bonding which will stick to almost any surface but it has to be a low suction background if in doubt about this use PVA watered down to about 3-1 this will considerably reduce suction ( suction is the rate which the water is absorbed ) if not as the bonding dries it will look like crazy paving. And lastly there is multi-finish or board fin. and thistle fin. the most used is multi-finish it's always advisable to use PVA except on plasterboard. Like decorating preparation is essential. I hope this helps.

Answer 5

too little water, too deep holes, too fast drying.

Mix it so that it has enough firmness to hold shape in the tub, you shoudl still be able to stir it easily. Mix thoroughly. Damped the hole/wall with a PVA solution to stop the existing wall sucking out out the water too quickely from the paster.

Apply it, shape it flat approximately, leave for 10 mins, re-shape the plaster and work until it is polished smooth. use a decent metal float. Unfortunately the new DIY-shop ones are too sharp edges and take a while to wear in.

Correctly mixed plaster shoudl be workable for half an hour so be patient. Work it as it dries.

If the cracked plaster is sound just leave it there and skim over it again.

Nice one ( for having a go )...good luck

Answer 6

Did you unibond the wall first. Plaster cracks for 2 reasond 1 put on too thick 2 dries out to quick.

Answer 7

your plastering has more than likely cracked because of to much suction this is also why you want to keep the skimming soft.the plaster is not setting to quickly the suction is sending it off.to control the suction and eliminate the cracking you need to apply a product called bond it,made by bg. you apply it with a roller or brush 24 hrs before skimming.you may have to order it into your local builders merchant but the results are far better than using a pva adhesive where the cracking would more than likely reappear.i am a director of one of the largest plastering firms in the uk so i hope i know what im talking about.

Answer 8

possible put on too thick or the wall was very porous,
or just dried out too quickly.
when plastering you should always put on a watered down pva adhesive directly onto the wall to be plastered ,then if plastering onto bare brick you should put on a render coat,different to finishing plaster,then put on a skim coat of finishing plaster(should be no more than 4-5mm thick with plenty of water thrown over with a brush and fine trowel ed for a smooth and shiny finish.
hope this helps

Answer 9

If you didn't mix it correctly, or if you applied too much at once, the plaster will crack. Like concrete, plaster shrinks as it cures.

Answer 10

Either you put it on too dry, or it has dried too quick. Plaster usually takes about 2 days to dry.