Need More Info about Patching Plaster


Old 03-27-06, 09:04 AM
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Join Date: Feb 2004
Posts: 17
Need More Info about Patching Plaster

I printed out and read the info on the Do It Yourself website about patching plaster, but I have some additional questions. I have some cracks that need patching. I brushed off all the loose plaster in the cracks. The biggest gap I have after doing that is less than 1/4 inch wide. The edges of the cracks are rough. Should I sand them or somehow scrape them so they're smooth? Also, there is a place near one of the cracks on the ceiling that has bubbled paint.....due to a leaky roof which has since been fixed. What should I do about that? Any advice will be apprecited. Thanks.
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Old 03-27-06, 11:49 AM
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I seldom do any repairs on plaster but you can use joint compound or durabond for small repairs. It doesn't hurt if the edges are rough as long as they are below the surface. If the plaster is dusty you should prime it first before patching. Any bubbled or loose paint will need to be removed. If there are any water stains they will need to be primed with a solvent based primer. Patch as needed.
Old 03-28-06, 01:28 PM
Join Date: Oct 2005
Posts: 51
You should also check the plaster where the water stain is, to determine if it is intact. Although a lot tougher than wallboard, plaster can get softened by long term expsure to water. I would peel off the bubled paint and try poking at the plaster a little to see if it is soft. Also try pushing on it. If it gives quite a bit, as if there is a buble underneath it, the keys (the plaster which pushes through the lathe at the back and holds them together) may be compromised. This may be why the crack started. When the plaster delaminates (separates fromt the keys) it tends to pull away from the lathe and crack. If the plaster is soft or delaminated, you will need to cut it out the delaminated section and replace it, or the cracks will come back. Also please be careful about possible lead in the paint when you peel it.
Old 03-28-06, 08:59 PM
Join Date: Nov 2005
Location: PA
Posts: 334
Originally Posted by eltee
Should I sand them or somehow scrape them so they're smooth?... Thanks.

Joint compound and setting type joint compounds love to hold onto rough surfaces, so I would leave them rough, jus make sure the dust is off of them.

Although they can usually be filled "straight up", you might consider putting a piece of drywall tape over the crack and feathering that into the wall; as often times cracks come back.

My .02 (.04 if it is a big crack)

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