Re skimmed plaster cracking

by Paul
(Maidstone Kent Uk)

We have recently built an Orangery and used a plasterer we have used before but on a small conservatory, the Orangery being a bigger area to plaster. After his first attempt of "hardwall plus skim" I wasnt really happy that he had applied enough Hardwall as after his finish/ skim coat I could see the electrician conduit through the plaster.I spoke to the guy and he siad he would go back pva the walls and re-skim which he did on Saturday(which was very warm day here in Kent). My customer has informed me this evening that their are now lots of small cracks all over the walls. What do you think has caused this? Any advise would be very helpful.

Answer

This has almost definitely been caused by the heat. The only way to avoid it in the future is to try to keep the sun off the wall and apply plenty of water up until the full set - to prevent it drying out too fast as well as ensuring the base is also as damp or sealed as possible.

Once this has happened it can be remedied quite simply by running a dry trowel over the wall. If there are very small cracks they will just fill in with the fine powder that's created and almost disappear. However if the cracks are a bit larger the only option is too fill them - which if there are too many sometimes it can be easier to skim the wall again.

Hope this helps. Please be assured that this problem is not unusual in excessive heat.