I have repaired a hole in Wall that was about 2" across using a piece of drywall bigger than the hole and removing the "chalk" part to fill hole, leaving the paper intact bigger than the hole instead of using tape and it worked very well. Now I have a hole in Ceiling of bathroom I need to repair about 8" x 10". (replaced vent fan but had to be installed in slightly different spot, new one bigger and wouldn't fit under a pipe of some kind in attic space..I don't know what its purpose, runs from front of house to back of house, white pvc, about 3" in diameter) I was hoping to use this same method but I need to think of something to keep it in place while drying.
My 2 ideas are:
1)once dry wall mud and dry wall in place put a slat across it temporarily to hold in place. But will the weight of it eventually pull it down or sag?
2)Use the slat on the backside attached with drywall screws so it spans across the "inside" and use option 1 also until dry.
With that big of a patch you will be happiest with a solid backing. I've done exactly this type of repair (after my foot slipped while I was walking in the attic!). If you don't have a backing, your repair may sag. For the backing, use a piece of 1/2" plywood or particle board. If you put it in from above, make it so that it is a couple of inches larger than the hole in both dimensions; if you're doing it from down below, make it larger than the hole in only one dimension so you can slip it through the hole. Put a temporary sheetrock screw part way through the center to have a "handle" to hold onto for the next step. Screw several sheetrock screws through the sheetrock around the edges of the hole so that they also screw into the backing material and draw it tight to the back of the opening. Then cut a patch of sheetrock to the correct size and just screw it to the backing. For a repair like this, I find that you get a flatter result if you don't use the overlapping flap method, but simply cut the patch to the size of the hole and finish it with paper tape and joint compound.
Yes, you will want some solid backing. You can either fasten plywood strips underneath or cut out to the nearest studs (for bigger holes). Both methods are shown in detail at the link below.
