Seattle, WA, US
Sorry. Disregard comment. I should have read the entire article.
Not much help without minimum or desirable dimensions.
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)
Subscribe to Fine Homebuilding magazine now and save up to 52%
© 2017 The Taunton Press, Inc. All rights reserved.
Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.
Start your subscription today and save up to 52%