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Hairline cracks in the plasterboard of a refurbished mid-terrace

In January 2013 I bought a refurbished mid-terrace house built circa 1900. The work was done by a developer between June and November 2012 and I am the first person to live in the property since the work was completed. I was told that the property was re-plastered throughout although I have a feeling it was just skimmed. There were a small number of hairline cracks in the plaster when I bought the property and the survey stated that these were just cosmetic, but the cracks have developed quite dramatically in number since, to the point where they are virtually on every wall, where they spread out quite widely, plus there a couple on the ceilings. There are some horizontal cracks at the very top and bottom of the walls which would seem to indicate shrinkage, but there also a number of them in the middle of the walls, some of which are in a general horizontal (across the chimney breast) or vertical (on the hallway wall) direction but some are also in a diagonal (recesses to either side of the chimney breast) and haphazard direction (on the hallway wall). Having read other discussions on the topic I'm starting to think that these are more than just shrinkage cracks and that the new plaster was only a skim and that either the original plaster is blown or that the bonding agent has failed. The cracks are only hairline at the moment and seem to be only developing in length and quantity. My question is if the original plaster is blown and/or the bonding agent has failed should I be concerned? Is the newly skimmed plaster likely to fall off the wall and thus needs replacement or repair or is this just a cosmetic issue? Thanks.

Response to Phoenix Plastering 06-Apr-2013:
Thanks for your advice. Sorry for the confusion, the walls where the plaster is cracked are solid brick and so must be of the 2 coat variety that you mention. There is a hollow sound when I tap near the cracks so it does appear that the plaster has come away from the wall in various sections. None of these sections seem particularly large, there are just quite a few of them. Due to the fairly large number of cracks, plus the rather large length of some of them (2 meters) I'm not sure that it would be practical for me to try and fill them all. Most of them are only hair-line and so I don't mind too much as you can only see them on closer inspection. However, if I do try to fill the more noticeable cracks using the method you have stated below, if the plaster has come away from the wall, would opening the cracks up slightly not possibly result in the loose section coming off completely? I'd rather leave them as a cosmetic flaw than cause further damage by trying to fix them. Thanks.

2 Answers from MyBuilder Plasterers

Best Answer

This can be a tricky one to answer im afraid. You say in the title that the cracks are in plasterboard, however i personally have only ever experienced such cracks in 2 coat (solid plaster) walls. You should only get cracks in platerboard work if the joints have not been taped correctly. If this is the case the cracks will be uniform throughout the room. From your description however i would think it more likely that they are solid walls that have been reskimmed. If this is the case it is quite normal and most annoying. They occur due to seasonal variations in air pressure, temperature and humidity. Walls expand and contract and this creates pressure, which is then released via a break or crack in the plaster. If you try knocking the wall with knuckles you can find out if the original plaster has blown or not. If it sounds hollow, it is possible the plaster has come away from the brickwork, but dont worry it is very rare for any plaster to fall off. Be aware though if the walls are indeed plasterboard they will sound hollow anyway. My normal advice would be to lightly open out the cracks with a knife to make them larger and fill them with a flexible filler, this should allow the wall yo expand and contract without it cracking again. Don't worry the bonding agent hasn't failed as this is a completely different pattern of cracks and appears as soon as the plaster dries. So in summary i would say dont panic and just fill them in. However it may be worth getting it looked at for piece of mind, all professional plasterers should give you free quotes and advice in the matter. Hope this helps. Phoenix plastering

Hi again, opening the cracks out will not cause any further disruption as it is only minimal and around 2mm deep so they will only act to bind the surface skim back together, not to lift the roughing coat from the wall. The hollow sound is very common and although not good, it certainly does not mean any plaster is going to fall off. What is very likely to have happened when the property was refurbished, as with many, is that the developer got the work done as quickly and cost effectively as possible. Which means a reskim. Its likely that all the cracks you are seeing were also on the original walls and simply skimmed over and are now coming back. In reality if the walls are severely damaged we normally recommend plasterboarding them to prevent such problems. I would probably recommend calling a local plasterer to see what advice they can give you, this will be free of charge. Either fill them or leave them, either way im pretty sure your not your not going to get any plaster falling off. Thanks again, phoenix plastering


Answered 8th Apr 2013

I would go back to your surveyor and request a free inspection if he said its cosmetic. He has a duty of care. Sound more like plaster has failed.


Answered 8th Apr 2013

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