Cracks in plaster

[philipb82]

Hello

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.

Thanks

Phil

 

[joe-90]

Yes. No probs.

 

[philipb82]

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?

Thanks

Phil

 

[1john]

Yes, to help control suction.

 

[philipb82]

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.

Phil

 

[joe-90]

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.

 

[philipb82]

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.

Phil