I am repairing 170-year-old solid masonry walls in my house. In some places the plaster is in good shape, in others it is crumbling down to the bricks. I have had good luck skim coating with various types of drywall compound, but now that I am down to the bricks in spots, I am wondering what the best material might be. I appreciate suggestions I have received from this group. However, I have never used Structolite, a material some have suggested. I have found the US Gypsum site and phone support to very poor “They’re all good.” Sounds like the Nutty Professor.
I decided to conduct a test of Structolite vs DW compounds to familiarize myself with their properties. I painted one half an old brick with a concrete adhesive; the other half I brushed with water just before the applying the mixes. I also painted some adhesive on fragments of both gray and smooth plaster. I applied the following to the brick and plaster: Structolite, Plus 3 DW pre-mixed compound, Durabond, and Easy Sand. Photos of the test are below.
I discovered that Structolite is very soft when cured, much softer than DW compound. It also seemed somewhat crumbly. It also did not seem to have the adhesive properties that the DW compounds have. All three DW compounds skimmed onto the surfaces equally smooth, and all stuck very well to all surfaces. The Quickrete adhesive did not seem to make much of a differcence. However, on the old gray layer fragments, it became clear that the new compounds can pull old material apart if the underlying material is not sound. I was quite surprised that the lightweight pre-mixed Plus 3 adhered so well. I have read that a setting compound such as the Durabond or Easy Sand should be used with fiber tape applications.
As expected the Durabond was harder and did not sand as easily as the other DW compounds.
Conclusion: Durabond seems much more substantial a material to build up a repair. I am concerned that the Structolite is too soft and crumbly. However, perhaps this might be seen as a positive attribute of Structolite if used as a mortar between the bricks. I am only now learning about matching mortar and brick hardness. Plus 3 compound right out of the bucket seems like a good alternative to all the mixing. Note: I have tried the new Plus 3 “Dust Control” formula and found it to be extremely hard. If patched in the same area as the other formula, it does not sand evenly. Beware.
I would appreciate any comments on my test, and thank you for your tips.
Marc
Replies
I am not at all certain of the properties of StructoLite on brick, but I would imagine that you need a bonding agent. And it may not be an appropriate use.
Keep in mind that there will always be some moisture where brick walls are involved. I had a brick chimney re-plastered where the previous owners had removed all the plaster due to a flashing leak. I believe the plasters installed rock lath first. I don't know how it was attached or spaced though, and that was the entire chimney, not a spot patch.
Bravo! Thank you for doing this and sharing your results.
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Structolite is as close to the original plaster as you're going to find on the shelf of the big box stores. If you're trying to build the wall out to the original thickness I don't believe the compounds are the way to go.It doesn't have the integrity that will be needed at the thickness you will be applying. The Structolite relies on the surrounding material to give it strength. The test application you performed did not have enough surface space to allow it to perform as it would in actual application. The compound is ok for small patches here and there or th repair a small crack, but to accomplish a project the magnitude you have described the Stuctolite is your material of choice.
I repaired a three story radiused-wall stairway that was water damaged several years ago and it turned out great. The Structolite is only the base coat and should be top coated with compound for a smooth finish. Keep in mind that this is only my opinion from my experience. I'm not a professional plasterer and there is alot that I don't know about htat dying art.