Mark the line of the ceiling joists above and screw the plaster to these. Use dry lining screws with large washers on them. The washers will prevent the screw pulling right through the plaster and can be sunk a fraction into the surface. Dry lining screws will cut through easily and grip well in the joists. I'm puzzled why the editors thought this was a good video to put up for viewing? It seems kind of like a discussion of how to make your own nails out of wire.” Get plaster washers. There was a time when there was only one major source (Charles Street Supply in Massachusetts, making them since 1948), but Googling "plaster washers" brought me dozens of possible sources, and also dozens of online discussions of these marvelous little devices - so it's not like they're unknown. As plaster ages, these keys may break away from the lath, and the plaster coating can come loose and sag away from the lath. Sagging is usually obvious. If you have sags in a plaster ceiling, press upward on the area with the flat of your hand. If the plaster feels spongy or gives under your hand pressure, it's a sign that the key strength has been lost. If it's not repaired, the plaster ceiling can collapse.

Save yourself time and trouble — make the patch a square or rectangle, even though the hole may be a different shape. I do appreciate the video however because you do preface it with "in a pinch", even though it's not a better way. I carry pipe strapping as well. I agree, plaster washers are the way to go when you have plaster that has lost it's keys. I've also used them to support big sheets of drywall on ceilings with 24" joists. The larger surface area makes me feel more secure and use less screws. If you look at the top side of a lathe and plaster ceiling you’ll see the lathes spanning across the joists. The plaster will have been trowelled onto the lathes so that it squeezed through the gaps and formed nibs. As it dried this will have formed a bond holding the plaster in place. This can get broken – most commonly in attics when work like boarding is carried out. Once damaged, the plaster below no longer has as much support from the lathes and can easily drop a little causing a bulge in the ceiling Small bulges in lathe and plaster

You now need to access the top side of the ceiling. For upstairs rooms, this is usually easy enough as you can get to it from the loft. For other ceilings, you will have to lift the floor in the room above to get access to the old lathes. If there is no termite damage or water damage this system is valid for professional results if all steps are done properly. If the sagging is slight, or covers a small area, you can reattach the plaster to the wood lath by using long drywall screws fitted with plaster washers. A plaster washer is a thin metal disk that increases the size of the head of a drywall screw so that it doesn't pull through the plaster. You thread the drywall screw through a plaster washer and then drive it through the plaster and into the ceiling joists, wall studs, or wood lath. The screw and washer pull the loose plaster tight against the framing, restoring the ceiling. By surrounding the area with plaster washers, you can stabilize the plaster so that it doesn't sag any further. First, locate the joists or studs and mark their location in the loose area. Push up the loose plaster and place 2-in. screws and the perforated plaster washers into the joists or studs about every 6 or 8 in. The convex washer will flatten as the screw tightens. If the plaster has a rough surface, you may need to first scrape the surface to get the washer to lie flat. Next, secure the loosened field to the lath between joists with more washers. Finally, skim-coat over the washers with drywall joint compound. It may take several coats and extra effort to create a smooth finish or mimic the existing texture.

You don't have permission to access "http://www.homedepot.com/p/Grip-Plate-Lath-and-Plaster-Washer-1000-Pieces-HDGPPWL1000/303868289" on this server. Roll a special topcoat over the fiberglass mesh if you use the Nu-Wal product; otherwise skim coat the mesh with two coats of joint compound. Be sure to cut away any protruding paper facing or crumbled gypsum core from the perimeter of the patch area.Once the sagging area of lathe and plaster has been re-supported like this, the recesses for each screw can be filled and the ceiling redecorated Larger areas of sagging ceiling I'm puzzled why the editors thought this was a good video to put up for viewing? It seems kind of like a discussion of how to make your own nails out of wire. Yes, I'd agee with the others. This is a decent tip for being in a pinch, but if you have an old house or work on them for others, you really ought to have a big bag of plaster washers. It's a whole lot less time consuming and they'll work better (bigger diameter, full of holes to key the skim plaster). I buy mine from Charles Street Supply (google) whose big quantity prices are a bit cheaper than Lee Valley. Seems like the Lee Valley price for 100 is good though.

I would use those Plaster washers instead, larger in size and work better on my house with 100+ year old ceilings. This is usually a problem caused when the plaster has lost its key. I have lifted a ceiling up over 1" and then taped. It is no fun to remove 1.5" of old plaster on wood laths.Allow the plaster to dry overnight before gently removing the timber supports below. The ceiling can now be redecorated Substantial damage repair

Clean away all the broken plaster from the area above and remove any other debris. Vacuum the area as well to remove as much dust as possible. Wet the area with clean water and a brush then make up a slightly sloppy batch of bonding plaster. Trowel this out over the damaged area so that it bonds completely with the old plaster and completely covers the lathes. Insert the wallboard patch into the hole and drive screws through the wallboard patch into each wallboard repair clip. To screw into the 2X4’s is a must to enable the washer to completely flatten out and support both drywall edges with it’s 1 inch diameter, otherwise without these washers, The drywall screws alone would only further weaken the drywall edge and create more damage.Diameter : 1-Inch, drywall screw goes through the washer and is driven into the wood lath behind the plaster The Hillman drywall washers are great! The pictures included illustrate how well they work, especially when combined with white Loctite power grab caulk adhesive and Kilz primer. If the sagging is severe, meaning that it's hanging an inch or more away from the lath base, or if it covers a large portion of the ceiling, your best bet is to remove the old plaster and replaster the ceiling, or cover it with wallboard. Not an easy do-it-yourself project.