Cracks in plaster

3 Dec 2009
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United Kingdom

I did some plastering about 3 months ago. I repaired some blown areas of plaster so i knocked plaster out back to brick, used hardwall then skimmed with multi finish. Anyway i have noticed some cracks and they sound hollow so i thought it had blown. I investigated and started raking out the crack but it seems sturdy. I had to hack it off instead of just scraping it off easily. To me it seems like its all bonded and holding well. Could i just dampen or pva the area and apply some filler and sand? Any advice welcome.


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Just another question if i may! When i've knocked plaster back to brick am i right in thinking that i need to seal the join of the old plaster? Then another application of pva for adhesion before using hardwall?


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What else causes cracks? I have noticed a few more in my plastering. So i have raked out a couple but the plaster seems to have bonded well, i have to hack at the plaster. So i presume its not blown so what could it be? I'm in no rush to sort them and i'm sure i did everything right but i'm curious as to why. Infact i did a patch up in my hallway and theres a hairline crack that runs along the joint of the old plaster and the new skim. Also i did another patch up with no cracks at all! I'll be sorting out more blown areas in another room and would like to have that crack free if possible.

They are shrinkage cracks. You need to use scrim tape between old and new to prevent it. I've seen it in the local pound shop.
Joe-90 - do you mean using scrim tape over the join of the old plaster prior to using hardwall and/or skim. Sorry for the questions.


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