Lime Plaster AGAIN - what to do for patching

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avjudge
Posts: 333
Joined: Mon Jul 02, 2007 7:29 pm
Location: Somerville MA

Lime Plaster AGAIN - what to do for patching

Post by avjudge »

I'd better finally patch my upstairs hall this summer before yet another winter's heat leaks into the attic & roof space (it's a Mansard so the roof is behind one wall).

I have holes where wiring was done - biggest maybe 9" x 3 feet along the top of one wall - and a large area (about 2' x 3') where the old plaster was apparently damaged by old movement (?). Both of these areas had been previously patched with drywall patches. The year I moved in the roof leaked and drenched this area. (That's been fixed, of course.) The old plaster came through well, but the paper on the drywall patches was black with mold by the time I opened it up for exploration.

I'm anchoring loose plaster using Plaster Magic, and I'd love to try patching with appropriate plaster. (Worst comes to worst and I stink at it, I can always knock it out and just do another drywall patch. :? ) But it's so hard to figure out what to do, since you can't just run out to a friendly local historic supply store. I've been reading here for a while (including HB's excellent posts), so I know lime plaster has been made using the lime available at masonry supply stores. But HB now says he's a lime snob and avoids that, and I come across "do not use" notes from the experts, like this:
http://www.preservationplastering.com/2 ... e-plaster/

SO . . .

I could just go ahead and make lime putty from lime I can get locally, like HB did in his earlier posts.

I could order something from a historic materials provider - Virginia Limeworks? Either lime putty or a Mix & Go mix (do I really want hydraulic lime?). I understand the shipping is expensive for something so heavy. Besides the lime, you're also paying to ship either water or sand, both quite heavy (but saving yourself some mixing labor, esp. with the putty).

I could order patching plaster from Rory "Big Wally" Brennan, the Plaster Magic guy - I just discovered today that he's added this product, made to be compatible with old lime plasters, to his product line. I assume it mimics the "don't say I told you, but..." builder's lime + structolite kludge he told us about at the NH old house & barn expo last year, after warning us in his talk that builder's lime does not make acceptable plaster. But it seems to be aimed at smaller patches - his larger container will only cover about 1/2 of my larger patch. (I should write & ask him about this!) Virginia Limeworks doesn't list prices on their site so I don't know how they compare, but this looks very expensive.
http://www.plastermagic.com/patching-plaster-released
http://www.plastermagic.com/order-now

I do have some hair I ordered from Virginia Limeworks before I realized lime is such a complicated issue.

I have searched the forums, and I haven't seen any new information recently, and not much talk of suppliers. Have any of you gotten into this? Where have you found your favorite product, and how much did it cost? (And I am right by Boston MA - with all the old buildings here you'd think there'd be more local resources.)

Thanks!
Anne
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Sombreuil_Mongrel
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Location: WV

Re: Lime Plaster AGAIN - what to do for patching

Post by Sombreuil_Mongrel »

Hi,
I wouldn't go with the mix-n-go, because the sand adds a lot of unneeded weight to the freight. Just buy their bags of lime, I think what we were using was called "enviro-ment"; you can make either interior or exterior mortar with it. Then source your sand locally, and I assume you have water on-site (!) and you're ready to mix. We cut the bundles of hair in half, because the 3" strands wouldn't mix n at all.

Update/edit: I double checked, and when I said "enviro-ment" I ought to have said "150".

Casey
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James
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Re: Lime Plaster AGAIN - what to do for patching

Post by James »

No expert here, and Casey please correct me if I say something stupid. But I don't think you need hydraulic lime, in fact I think you want to avoid it. Hydraulic lime will set in the presence of water, meaning that if you mix it and then don't use it promptly it will go to the bad. Non hydraulic lime will stay good as long as there is water on top of the putty in the bucket after you mix it. For a very long time provided the water is there on top.
Last summer I took a plaster repair class at the Community College, we were repairing a ceiling in Stonewall, the local house museum. The plaster was mixed on the first day of class, and by morning of the second day had to be thrown out, it was to hard to work, and a new batch mixed. I say avoid hydraulic, and go with non hydraulic. You may be able to get that locally. When I ordered some from Virginia Limeworks a few years back I paid if I remember correctly $130 something for three bags. Of course that was only shipping to North Carolina, not so awfully far.
As long as it takes me to get around finishing some projects, I would never go with hydraulic.
Locust Quarter, circa 1770 Georgian Gambrel roofed cottage.

avjudge
Posts: 333
Joined: Mon Jul 02, 2007 7:29 pm
Location: Somerville MA

Re: Lime Plaster AGAIN - what to do for patching

Post by avjudge »

Thanks, James & Casey - I thought I didn't want hydraulic, and that's all that VLW seems to sell dry. Putty (bought or homemade) that gets better with age sounds more like my style, as I'm likely to start a project and then get side-tracked! The enviro-ment has frustratingly little info on it online ("Available spring 2008 - check back soon!"), but is listed as a mortar, "available in type M, Type S, & Type N," which doesn't sound right for plaster.

James, do you remember what you ordered from them? I should probably just call and ask instead of relying on the web site, I just hate talking to people until I know that I won't sound like an idiot! Which is bad, I know I shouldn't be afraid to sound like an idiot because that's how you learn, but knowing that I SHOULD doesn't make me more willing to pick up the phone -- one of the downsides to being the risk-averse perfectionist star student type.

The lime putty sounds like what I want but then I'm paying to ship water. (Well, also paying to avoid the mixing work, and since tennis elbow just appeared in my left arm - a year after it went away in my right - maybe that's not so bad. I think it took something like 6 months for my right arm to recover. Maybe it would be a really good idea for me to get pre-made putty, though I'll still have to mix in hair.)

At his talk last spring Rory Brennan was so definite that the lime you get at the standard building/masonry supply house is inferior for plaster that I'm scared away from that. (His suggestion for using it was to mix in a bit of structolite to the lime, little enough that it stays soft enough for compatibility with the old - and he then last fall came out with his own patching plaster blend which sounds like the same thing, but $$$.)

Why is this so complicated?????

Anne
Anne
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Sombreuil_Mongrel
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Joined: Sat Sep 30, 2006 10:12 am
Location: WV

Re: Lime Plaster AGAIN - what to do for patching

Post by Sombreuil_Mongrel »

The stuff you mix with water to make lime putty is called "autoclaved finish lime". You can get it through just about any local masonry supply.
Casey
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Texas_Ranger
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Re: Lime Plaster AGAIN - what to do for patching

Post by Texas_Ranger »

Seriously? Use what you can get!
If you were plastering real soft brick walls or (even worse) pointing exterior brick I'd be concerned, but if you just want to patch a plaster&lath wall I'd say you can use pretty much any type of lime. $130 for 3 bags of lime sounds flat out insane to me, should be more like $13. I mean I chiseled 33 years worth of cement plaster off of late 19th century soft brick and even adobe and the only damage was where the adobe got moist and froze.
The bad thing with electricity : it almost always works.

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