drywallplaster
So I just removed staple on ceiling tiles from my curling to find they were done on top of plaster, my questions are:
1) is there any fear in any case of the drywall adding to much weight to the ceiling? This house was built in 1908.
2) when installing the drywall do I attach along the furs or along the studs or where the fur overlaps the studs? The old tile where 12×12 so the furs are 1 ft spread if that makes any difference.
Go ahead and place the drywall over the top edge of the crown moulding. Sounds like the wall was already re-plastered with it in place. If you tried to remove it, you may end up re-doing the walls as well. Even forgetting that, it's almost impossible to remove moulding without sustaining some loss. Without replacement material available, removal with intents of preservation is extremely risky, especially with stain grade material. You don't want to go there.
If your joists were flat, you'd still only need to shim down the first 4 feet or so along the walls, no one will see the resulting slight slope. Keep this in mind when planning your shims. It doesn't have to be perfectly flat, unless that gives you pleasure. You also don't need to shim to completely fill the gap. An 1/8" gap makes a clean shadow line that is not detrimental (assuming it is perfectly uniform) at all. It also makes finishing easier. The taped joints of drywall are normally not perfectly flat, despite the tapered edges. There is a slight bulge which is usually invisible. But against straight moulding, depending on the profile, this bulge may be visible. You might consider grinding down the edge tapers at the board corners against the wall so the joint tape can be completely buried and the yet the joint against the moulding can still be perfectly flat.
I wouldn't try removing the frame. It appears to extend in both directions and may damage a larger section of wall.
You are right to be concerned about taping compound or spackle sticking to a metal edge. I would recommend making a patch that is larger than the opening by about an inch on each side. Then trim away the back paper and the core of the patch so that the part being put into the wall is the exact size of the hole. That will leave you with a "flange" of paper facing on hte room side that will be easier to tape and compound to blend it in.
Your general approach to support is right, but you may not need a brace between the studs. To support the patch, cut three pieces of 1x2 wood that are about 6 inches longer than the height of the opening. Position each piece of wood vertically in the cavity, one near the left side of the hole, one in the middle, and one near the right. To attach each strip pull it forward against the back of the plaster or plasterboard. Hold it in place by screwing through the face of the wall into the top and bottom sections of the wood strip. You can screw the plasterboard patch to these strips for support.
Finish the attachment with tape and taping compound. I would probably use mesh tape on a patch of this size and support.
Best Answer
Hanging drywall over old plaster is very common. If the existing strapping is securely fastened to the ceiling, you should be able to hang sheetrock. I use 3/8" rock all the time over plaster walls and ceilings. The weight is not an issue. You may want to check, using a stud finder to assure yourself that the strapping is attached to the underlying floor or ceiling joists. It certainly would not do any harm to find the joists and add a screw into the strapping to be sure it is secure. The only time you might have a problem is when the strapping is only connected to lathes, and if the weight of the rock held only by lathes may sag if the lathe nails are not secure into the joists. Good luck, go for it!