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Theres a Better Way

Secure Old Plaster in a Pinch

comments (16) March 25th, 2010 in Blogs
grateful.ed Chuck Miller, editor at large

Video Length: 2:09
Produced by: John Ross, Edited by Cari Delahanty

Don Mathis writes:

Often sagging plaster needs to be secured and stabilized. One common method is to add a mechanical support with a dimple washer, a concave washer that literally holds the plaster in place. However, if you're on the job and don't have a washer specially designed to secure plaster, you don't have to stop work for an extra trip to the supply store. You can make your own washers.

I make my own plaster washers using a section of plumber strapping (metal strapping perforated with holes for fasteners). First I shape the strapping into a dimple shape around a hole using a ball peen hammer against a gouged piece of wood. Then I trim the strapping into a small disk that is now concave.

I use a Dremel tool with a diamond disk to make the the recess in the plaster to receive the washer. Be sure to use some sort of dust mitigation as this part can get messy. Secure the washers in the recesses with drywall screws.

After installing the mechanical supports, I cover the secured portion of the ceiling with adhesive-backed fiberglass on a 36-inch roll then start the skim coat.

posted in: Blogs, remodeling, restorations
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Comments (16)

Bcramer Bcramer writes: Why use plumbing tape? Just take regular flat washers, put them in the same jig and ball-peen them into shape.
Posted: 9:42 am on May 17th

jyang949 jyang949 writes: What is securing the screw--the wood lath behind the plaster? Can plaster washers be used when the lath is wire mesh?

Posted: 11:55 am on April 20th

grateful.ed grateful.ed writes: “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.”

Here’s why. A tip is about creative improvisation. A good tip takes some common thing, and finds a new use for it. Yes, plaster washers are commercially available, but if you just need a dozen to reinforce a cracked ceiling, and you don’t want to wait three days for delivery, this tip can help you out. And if you’re new to patching plaster, and have never seen this method, simply learning about the concept is useful.
There are always going to be better ways to do a given homebuilding task (we’ll never call it “best way”), and that’s why we invite your comments. They enrich the dialogue, and make each tip that much more useful. And if I’m stuck on an island someplace, with a roll of wire and a boat that needs repair, I’ll figure out a way to make nails.

Posted: 1:38 pm on April 2nd

WoodLess WoodLess writes: It's been said by everyone else, Plaster Washers. I have a 100+ year old house and keep a supply on hand. I can only say this was a waste electrons for the video.


Posted: 5:21 pm on April 1st

Houghton123 Houghton123 writes: On a lot of plaster, the finish coat maintains its strength long after the scratch and brown coats have gotten flaky. This tip proposes to remove that strength by chewing out a divot, increasing the chance of cracking in the process, AND has a worker making washers that you can buy at about $5/100 (how many workers could make 4-500 of those an hour, to justify the wages?).

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.

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.
Posted: 2:26 pm on March 30th

scb700 scb700 writes: I used the aluminum plaster washers (a bag of 100 about an inch in diameter I got on line years ago from a mail order house, in Boston, I think). My 90 year old house had cracks running all over the ceilings. I used a 1" spade bit to create a depression about an 2 inches away from both sides of the cracks and about 6" spacing, and opened up the cracks about 1/8" so the new plaster would penetrate. I was afraid that because the spade bit cut through the existing old skim coat exposing the rough plaster coat and reducing the thickness of the plaster that the washer would be supporting, that this might not work every well. I taped and plastered over the cracks and washers and it has lasted for years with no new cracks having reappeared to date. My cracks ran across the entire ceiling from wall to opposite wall in several places so it was more than a patch or quick fix. I can't see a professional taking the time I did, but it does work (I didn't want the mess of knocking down the old cracked ceiling and putting up dry wall or adding the weight of dry walling over the existing plaster ceiling)
Posted: 6:54 pm on March 29th

buckyball buckyball writes: Floridians concerned with the coastal humidity festival and rusting steel in plaster might use thinnest stainless sheet scrap in the same way. I haven't looked, but I can bet ss specialty washers aren't available, two days late, or are a quarter each plus shipping and handing. Pan head ss washers are probably too heavy for easy cold forging, although if one uses a flat head, it might be, ah, self-countersinking. One can also use a stainless pan head/small washer to over-tighten sheet into the die, which avoids carbon steel transfer to the stainless, probably an over-analysis. However, consider the effect of the steel hammer on the galvanized layer as shown, usually very thin on the plumbing strap aside from the raw edges. I note "self-depressing" above, also the comment about rust "pops." Good tip for those of us with chaotic garages who "work in" a lot of stuff in multiple locations. (It takes a few years to season inland newcomers, and even if they care there often are no good solutions, so these rust/corrosion problems do come up from time to time.)
Posted: 5:54 pm on March 29th

Dave_R Dave_R writes: 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.

On another note, I have a lot of walls where only the topcoat of the plaster is loose and flaky. I'd love to hear some expert opinions about better ways to handle this problem. Right now I'm scraping the loose topcoat back to solid material (which sometimes results in huge patches of missing plaster) and using the fiber mesh sheet/skim coat methodology described here.

Posted: 12:43 pm on March 29th

SidMo SidMo writes: 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.

Peder is dead-on in another regard too. I don't think you want the washers right on the fracture line! Rather you want to stagger them down both sides of crack an inch or so away from the actual crack in solid undamaged plaster. Holding both sides up with 1 smaller diameter homemade plaster washer right on the weak damaged area seems like a bad idea... Use a lot of real plaster washers to give solid support. You are reskimming anyhow -- make it last.
Posted: 11:48 am on March 29th

DougY DougY writes: My 100+ year old house has given me the opportunity to use lots of plaster washers. I use 1 1/2" spade bit to cut a slight depression and reduce the thickness of the skim coat. I also try to place as many of the screws in joists as possible because the lath won't always hold the screw.
Posted: 9:06 am on March 29th

Jercarp Jercarp writes: I use plaster washers all the time for this very thing. They're cheap and come in bags of 100. I keep them in my truck so they'll always be on hand.
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.
Posted: 7:56 am on March 29th

Peder Peder writes: I think this is right up there with making a motorcycle out of wood. Yes, you can do it but why bother. Anyone working with hard plaster should have a supply of plaster washers (they are cheap). As for cutting all the divots in the old plaster and on the fracture edges no less, that is a relatively weak support. Better to move back from the edge, drill a small pilot hole with a 1/8 masonry bit and run in a screw with a plaster washer. The washer spreads the lifting force over ~2" of surface without compromising the strength of the surface. It is true that the washer stands slightly tall of the surface but that should be skimmed over after taping.
Posted: 12:50 pm on March 28th

dequintess dequintess writes: I have had great success with the plaster washers. The one I used were "self-depressing" as they are screwed into the lathe. This has the great advantage of not having to make indentations in the plaster which can cause further cracking or loose pieces breaking off. The only difficulty is finding them in any of the major hardware stores, but they can be ordered online from Lee Valley Tools ( - item number 67z20.02)
Posted: 8:08 pm on March 26th

garfieldsimons garfieldsimons writes: And what keep the raw steel of the strapping from rusting over time and bleeding through?
Posted: 4:00 pm on March 26th

unomagnmus unomagnmus writes: 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.
Posted: 3:09 pm on March 26th

cernunnos cernunnos writes: Great tip! However,having grown up near there I am sure Don will appreciate the correct pronunciation of Macomb next time. The emphasis is on the second syllable: muh•COHM.
Posted: 1:04 pm on March 26th

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