[nowwhatnapster]

I need to repair a 4 inch hole in a plaster ceiling caused by water damage. It was a slow leak ignored by the previous owners. It was caused by a bent nail on the asphalt roof that poked through the top layer of shingle. I fixed the leak. The plaster directly below the nail was brittle so I chipped it out and was left with an irregular 3-4in diameter hole. The plaster ceiling is from the 50's smooth in texture and is on a gypsum backer (no lathe).
How would you patch this?

I also have several 5in diameter clean cut plaster rounds from recessed lights at my disposal.

I was thinking of squaring off the damage and screwing wood/drywall to backside then screwing a square patch into the backer. I was thinking of using the plaster rounds mentioned above for patch material to avoid a height difference. I would proceed to taping the joints with paper/joint compound (sheetrock brand with green lid) and Sanding / applying more compound until smooth. I read somewhere that it may improve joint compound adhesion if I applied a latex primer prior to patching.

This will be my first attempt at plaster repair or drywall repair for that matter.

 

[ToolSeeker]

First I would suggest glue for your backing instead of screws the plaster around the hole may be brittle and screws may crack it. I have never found primer to help mud stick, some rough sanding yes. I would also use hot mud for at least the firs and maybe 2nd coat. Hot mud is a powder you mix with water and has a drying time on the bag 20 minute 45 or 90. This has the advantage of quick drying and is stronger than pre-mixed. The disadvantage is a lot harder to sand so use pre-mixed for top coat.

 

[nowwhatnapster]

Glue crossed my mind but I didn't give it much thought. Only issue with glue is applying pressure to the backside to seat it. I don't have access to this area in the attic. It is in the eaves. I suppose I could put a screw or two into the backing material and pull down on the screws. Then remove the screws once the glue has set.

Would something like Liquid Nails Heavy Duty do the trick?

I'll skip the primer and sand any smooth spots around the patch to get good adhesion then.

As for the dry mud, you are referring to something like this USG Structo-Lite Basecoat?

 

[ToolSeeker]

Glue crossed my mind but I didn't give it much thought. Only issue with glue is applying pressure to the backside to seat it. I don't have access to this area in the attic. It is in the eaves. I suppose I could put a screw or two into the backing material and pull down on the screws. Then remove the screws once the glue has set.

Would something like Liquid Nails Heavy Duty do the trick?

I'll skip the primer and sand any smooth spots around the patch to get good adhesion then.

As for the dry mud, you are referring to something like this USG Structo-Lite Basecoat?

Sounds good yes the liquid nails will work
The dry mud is USG dura bond It's in the drywall dept with the pre-mixed.

 

[oh'mike]

Tool Seeker---Do you mean Durrabond?? Brown bag?

Or Easy Sand--White bag?

Many drywallers use the wrong name for Easy Sand---and mistakenly call it Durrabond--which is used for exterior work and high moisture areas--and dries hard as a rock--Mike---

 

[ToolSeeker]

Tool Seeker---Do you mean Durrabond?? Brown bag?

Or Easy Sand--White bag?

Many drywallers use the wrong name for Easy Sand---and mistakenly call it Durrabond--which is used for exterior work and high moisture areas--and dries hard as a rock--Mike---

Sorry white bag. brown bag like concrete but non sandable. Use the white bag.

 

[nowwhatnapster]

A little update with pictures. Who doesn't love pictures? I picked up some 90 minute sheetrock brand setting type joint compound (white bag). I figured 90 would be good for a novice like myself. Also got a tube of the liquid nails heavy duty.

I started squaring off the damage with a drywall saw. I scored and taped the plaster with a utility knife to prevent cracking. The final patch size is about 5-1/4" square and there is a rafter directly over the left side of the patch. My 5" plaster rounds are too small for patch material.

I picked up some regular 1/2" drywall to use as a backer and for the patch material, but then I realized my ceilings are about 3/4" thick. So 1/2" drywall would leave a 1/4" discrepancy in height. What would be better, going back to the store and return 1/2" for 3/8" drywall (screw/glue two peices together) or just use the 1/2" drywall and fill the 1/4" height difference with mud?

Also, how much of a gap should I leave between the patch and the plaster? Should I go for a tight fit or would a wider gap filled with mud be better?

After scraping loose paint and plaster:

Closeup

Taped and scored

Starting cut, rafter is on left side, i stopped cutting there and intend to finish with a dremmel.