I couldn’t easily find an answer to this in an old thread. I’ve got to patch a hole (about 1′ x 1′) in a rock lath wall. By rock lath, I mean the walls are a layer of sheetrock (I think maybe tiled sheets of 16″ x 48″) covered with a brown coat of plaster and then a thin veneer white coat of plaster. The walls are great, strong stuff.
I’ve got to build up about 1″ of material from the studs and HD and Lowes don’t carry rock lath sheets anymore so I was thinking I’d use
1&
#39;x’1′ piece of regular sheetrock, attached to the studs (for some reason there’s an extra stud at the hole – how lucky). Then two furing strips of wood, which I assume can be anything. Then some metal lath and lots of patching plaster with some PlasterWeld. I’ve never patched a hole this big before or one that goes through to the studs. Any idea if this is overkill or any better ways?
Also we are painting so I’ve got to somehow get the patching plaster as smooth as the surrounding veneer plaster – maybe a top coat of Joint Compound??
Thanks for any tips.
Replies
Put the sheetrock up backwards(brown side out). The plaster will get a better bond. If you are going to finish with topping compound I would recommend using hot mud as a base. Use a filler coat the mesh it with fiberglass, skim it and top it. If you are using plaster stay use Structolite for fill, fiberglass mesh at seams and imperial or diamond plaster as a topcoat.
Here is a link to a similar topic about a D-mix patching compound. Looks like something to try. http://forums.taunton.com/tp-breaktime/messages?msg=54559.1
Owen Roberts Group
10634 East Riverside Drive # 100
Bothell, WA 98011
http://www.owenrobertsgroup.com
Here's what I would do: Use the furring strips UNDER the drywall patch so the drywall will be just shy of the wall plane. Install the patch with screws and glue (joint compound can be used as the glue). Finish off with setting-type joint compound.
If you really want that hard plaster finish, you can finish off with plaster patch, but I found the stuff hard to work with. The last time I used it, I mixed it 50/50 with setting type joint compound. It made it a lot easier to work and it was just about as hard as the plaster itself.
If there's any chance of the edges of the patch cracking and telegraphing through, then I would tape all of the seams and feather it out with joint compound.
I've fixed a lot of holes in plaster just using joint compound. After priming and a couple of coats of paint, they disappear. Granted, it is not as hard as plaster, but unless someone is playing handball against the walls, I don't think it really matters.
-Don
Holey Moley!
I am in the exact same situation, was about to post for ideas on how to do this. My hole is about 8" X 36" (ancient cast iron soil pipe is toast). I had considered a double layer of 1/2" sheetrock coated with D-mix.
Any other suggestions?
I recently plugged and made vanish a large number of 2"X4" through 8" x 8" holes in walls of exactly your type. (post-wiring).
As often as possible, I saved the pieces that had been cut out (exactly the right shampe and thickness). Or, I cut new plugs from drywall and filled the depth later.
In place of firring strips per se, I used glued up pieces of stiff cardboard (boxboard) to the back of the existing wall. This was a bit fussy and involved cupping the board a bit to get it into the wall. I afixed them so that they spanned the whole gap in a couple of places, or all four corners. This created a rear, or back, surface to the holes. I used construction adhesive, and let it set completely.
Then I put adhesive on the back of the 'plug' pieces and pressed them into place against the cardboard, and got them flush to the front. When this adhesive set, I squeezed hard-setting compound into the gaps all around the edges -- using a plastic baggie like a cake-icing bag. I gently troweled any excess off the front before it dried.
This made a really solid and level patch, which was easy to skim over. Prime. Paint. I ask people to find the holes with a flashlight to the wall. They can't.
Overall, I had perfect success this way, and without tape. Holes where I've used mesh tape or patches always show as a hump, despite feathering out (shows at the baseboard, for example). I have had no gaps or cracks, yet. I did not attempt this on ceilings.
I have photos, but they are a little embarassing because the compound I had for the "cake icing bag" was the stuff that is lurid pink until it is dry.
Easier than messing with furring strips:
If you can flush cut the plaster to the outer studs, then you can simply sister on a 2x to create the proper depth. Then you can block across with strapping to support the top and bottom of the repair (if needed).
If it were me, I would use blueboard, and set the depth for about a 1/8 skim coat.
If I do use patching plaster - which I prefer greatly to joint compound for the fill - should the patched piece be blueboard? I thought blueboard was strictly for veneer plaster - is it okay to use it with patching plaster and/or joint compound?Is regular (gray) sheetrock bad to use with patching plaster?I've got 2 studs behind the hole so I shouldn't need to use the furing strips to hold the patch in place - but I will use them behind the patch, as many have suggested, to bring the sheetrock piece closer to the surface.Thanks for all the great tips. I'm glad no one suggested using the metal lath - what a pain that looked to be! I guess plasterweld will have to be enough to hold the patching plaster in place.
"If I do use patching plaster - which I prefer greatly to joint compound for the fill - should the patched piece be blueboard? I thought blueboard was strictly for veneer plaster - is it okay to use it with patching plaster and/or joint compound?"
Blueboard just has good 'tooth', and is a bit more rigid. Standard stuff will probably work ok.
Rock lath has a bonding agent manufactured into the surface. If you use regular wallboard, it might be a good idea to lay some acrilyic bonding agent on it, which you should do on the painted surface anyway.
if your hole is 12"x12" then install furring strips which are larger than the hole by at least 2" to 4" on each end to the back of the rocklath by screwing drywall screws through the face of the plaster into the furring.
fill in hole with 5/8" drywall (1/2" is fine)
using a 2" scraper, scrape 2" of existing plaster white coat off around perimeter of hole
mesh or paper tape seam of plaster to drywall
mud entire patch with durabond or ez sand
a second coat of this may be necessary
finish coat with bucket mud
this has been my standard practice for 20 years for those customers who aren't plaster purists
carpenter in transition
Tim Kline's is the right and standard way, when you have room to manouever the firring strips and tape the edges. It doesn't fail.
(I did as above only because of confined spaces - and a true hack like me can crack a lot of rock using DW screws and having to stay close to the cut edges.)