Hello, we had a couple of walls re-skimmed about 6 weeks ago. I've noticed several hairline cracks and the skim sounds hollow when ive tapped it. I got the plaster back round and he said it was the old backing plaster. However ive removed some skim around a crack and the old skim seems fine. Also he just said to fill the cracks! Any suggestions what could be causing these cracks? Thanks, Phil
New skim cracking
- Thread starter philipb82
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Is it just the new skim that sounds hollow (blown) or was the original plaster blown? Was there any cracking or crazing in the original plaster prior to the re-skim? Any serious cracks have to be properly repaired & blown plaster removed before any new plaster is applied, putting a new skim coat over original blown plaster or anything other than light surface cracks in the original skim (after reinforcing) will not achieve anything. If it’s just the new skim that’s blown & it’s also fairly easy to pick it off then it hasn’t adhered to the original base & this can only be due to incorrect or a lack of preparation by the plasterer who did the work. He can’t just blame the original plaster base he’s skimmed over unless that was also blown in which case he should never have plastered over it in the first place or at least not without advising you the probably consequences. Filling the cracks may or may not be successful (which he should be doing not you) & it rather depends how extensive the problem is but if it’s a general adhesion failure of the new skim coat, the whole lot could start popping off before too long.
Even the best of us have made mistakes at some time or another but if he’s made one, he should at least own up to it & put it right for you; that’s if he’s any good of course.
Even the best of us have made mistakes at some time or another but if he’s made one, he should at least own up to it & put it right for you; that’s if he’s any good of course.
The old plaster was painted and didn't have any blown areas or many cracks. They said that they taped any cracks that where present. I watched them do the work and they used pva before they skimmed. I think maybe it was a poor job!
What was it painted with? Don't take it the wrong way but is yours a smoking household?
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Sometimes it’s advisably to key painted surfaces but matt emulsion would not normally present any problems. You say they PVA’d the walls, don’t suppose you know what PVA/water ratio they used? Did they PVA the walls twice & skim while the 2nd PVA coat was still tacky or did they skim over dry PVA? Is the paint coming away with the new plaster when you pull it off or is the plaster coming away clean?
Only other thing I can think of is that the walls themselves were contaminated with something; were they previously wall papered & if so was all the old adhesive thoroughly removed? Were any sort of sprays previously used in the rooms concerned such as silicone polish, hair spray, deodorant etc? Or perhaps the PVA they used was in some way contaminated!
Only other thing I can think of is that the walls themselves were contaminated with something; were they previously wall papered & if so was all the old adhesive thoroughly removed? Were any sort of sprays previously used in the rooms concerned such as silicone polish, hair spray, deodorant etc? Or perhaps the PVA they used was in some way contaminated!
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Thanks for your reply. I don't know what mix of pva was used. Also the plaster is coming clean off with a scraper! The paint however is stuck to the plaster. Anyway good news, they are coming back tomorrow to reskim the affected area. Thanks for your help. Phil
Which plaster is the paint sticking to, the back of the new skim coat when it comes off or the original wall. If the skim is coming away clean (no paint), it indicates you’ve minimal adhesion of the skim coat to the original finish which is a prep problem. If the paint is sticking to the back of the new skim then there’s a problem with the original paint adhesion & the new skim bond will only ever be as good as the bond between the paint & the original wall. Before skimming, I always do a Selotape/Gaffa tape test on any paint covering to see if it’s actually stuck to the wall, if not you can take action to remedy before you plaster. Chances are it’s all the same so not sure how long it’s going to last before the rest starts blowing off the wall.
The old paint under the skim hasn't come off, that is firmly stuck to the old plaster. The new skim has come away clean with the new paint stuck to it. I sealed the new plaster with watered down emulsion first. Phil
Rather depends if it’s just a localised problem or not. If they skimmed over dry PVA for example or there is some underlying problem with the preparation or general contamination, the whole lot will most likely have poor adhesion; you could try testing the skim in other areas & see what happens.
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