Crack in corner wall

[zenonithus]

Hey all,

I have started renovating my recently purchased flat. Starting with the main bedroom I found a small crack running up one corner.

Looking closely it looked to be a repair, so I took off the plaster with a Stanley knife. It looks like there is a gap between the adjoining wall. Structurally the outside wall looks fine so it is where the two walls meet inside.

What is the best way to repair this? I was thinking filling the worst areas of the gap with cement then just rendering over that with pink render plaster. Though would I need some sort of joint tape to stop further cracking? Any advice would be great.

 

[roughcaster]

I've repaired a good few cracks like this. The way that I do it is this. Cut away about 5 or 6 inches of plaster all the way up the corner, on both the walls. Give the area a good brush down to remove all the dust and loose rubbish. Get some wire lath, cut a strip the height of the room, by about 8 or 9 inches wide, and bend it neatly, the whole strip, into the internal corner as you go,, half, 4 inches,, on one wall, then half, 4 inches on the other. Starting from the top, fix the wire lath securely to the wall, using galvanised clout nails, (plasterboard nails). Fix all down one side first, then push the wire lath tightly into the corner, then fix again down the other side, with clout nails. Make sure the wire lath is sunk in beyond the flush of the original plaster surface. Once you have the wire lath tightly and neatly fixed all down the internal corner, (tied in), give the whole area a good dampen down, and scratch it in with a 5 sand/1 cement, mix of mortar with a measured, small amount of waterproofer in the mix. Scratch it in, keeping the scratch coat about half the thickness from the finished surface. Let the render scratchcoat set for a day or so, then mix up a small amount of bonding undercoat plaster, and coat the patch out more or less flush. Let it set, then fnish it off with multi finish,,,, job done. A good strong, tied in corner, all plastered, and ready for decorating when it has dried out.

 

[zenonithus]

Great! Thanks for the advice roughcaster. Yeah I think that would be the proper way to do it to stop the crack from forming again. Do you know what causes these sort of cracks if the outside wall is fine? Also what sort of waterproofer do you mix in with the cement?

 

[chris1982]

If it's gypsum plaster, don't put cement on it as the two will react.

 

[roughcaster]

If it's gypsum plaster, don't put cement on it as the two will react.

Exactly,, gypsum onto cement, but not cement onto gypsum.