Repairing Plaster

Paul,

I hope all is well with you! Thanks again for the class.

We were removing tile from an interior kitchen wall and the tiles seemed to pull off the plaster down to the wall substrate / sub wall in the picture attached. It is reddish (similar to brick) and very soft, i.e it crumbles into dust if you scratch it with any hard tool. Any idea what it is? Also should we use the bonding coat over this before plastering with multi finish? Finally, the tile was only a backsplash so it only took up about 30-40cm in the middle of the wall - would it be ok to just plaster this section or does the whole wall need to be redone?


Thanks in advance for any assistance you can provide!


Cody

Answer


Hi Cody,

It's hard to tell but looks like it could be a decorative cement coating.

Apply a coat of PVA and then put the bonding coat in, using a straight edge to level it with existing plaster, by keeping either end of the straight edge in contact with the plaster you're joining to. Ensure nothing is sticking proud of existing plaster level.

You can patch it but it can take some time to join up to the existing plaster:

As the bonding coat begins to set try and scrape back the edges by about 1mm to allow for a thin coat of multi finish. When applying the finish first of all make sure that you concentrate on the edges by putting the plaster in the patch only. If you get plaster on what you are joining up to scrape it off so that you never lose sight of the edges and make sure the finish plaster is only very thin - so that you are not proud of the existing. Continue to keep edges clean with your paint brush as you go through the stages of trowelling, and fill any holes.

Paul