I’m stripping wallpaper from my house, built around 1910 or so. The upstairs has a rough finish, described by a friend as the “first coat” of plaster. Why it was not created smoother is unknown. Question is, can I use normal drywall mud to skim coat the plaster, or must I use something called “Plasterweld” (that is something I heard about). How is it used? I suppose I could just leave it, and create a textured wall finish, but I”m told not to mix anything on top of plaster. Thanks!
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Replies
If your plastering skills are as unrefined as mine, use drywall compound so you can sand it smooth. It should adhere very well to the rough plaster. If there's an issue with any remaining wallpaper paste residue, I'm unaware of it.
I use setting-type compound which comes in powder form, and needs to be mixed with water. It cures a lot faster than the wet stuff.
On my current jobsite, a plasterer visiting from Scotland was repairing plaster walls, and skimcoating entire ceilings. He was using a finishing plaster, but said if that's all he had available back home, he'd be a drywaller. In Scotland he uses a product called "Multi-Finish" by British Gypsum.
Allen
Aye, good news from Scotland. I was told the drywall compound would not adhere properly to plaster. Any thoughts?
Would it make sense to rough up the surface before application of any building product? Would straight " plaster of paris" do the trick? I'm trying to do a similar repair and I can't decide what , or how to go about it either.
Plaster of Paris will set up WAAAY too fast to use for most repair applications, skimming in particular. That's what they use to put plaster casts on broken limbs. Also mold and pattern making.
Patching plaster (sold in small cartons) and guaging plaster would be more suitable for wall and ceiling work.
I saw this stuff called "speedy patch" made by mission building products. Anyone ever use this stuff? There isn't that many different kinds of repair stuff for plaster , I can't find button board ,etc. This house is about 100 years old and the customer wants everything to be as original as possible. But it's turning into a nightmare.Countless layers of (probably lead) paint. and she wants a skim coat after the patch work is done.Is that even possible without grinding some "scratch" into the wall surface? how about masonry/plaster glue? Any one got any ideas...I'm all ears.
Go Angels
Plasterweld should give you the bond. I've never scatched the wall before applying. Thus far, no bond problems.
#### the angelsA great place for Information, Comraderie, and a sucker punch.
Remodeling Contractor just outside the Glass City.
Quittin' Time
I coat the surface first ( well, actuially I clean and rinse first)
with a bondiing agent. That will give a better bond than otherwise
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I have skimmed plaster walls (both over rough coat and fine finish) with good results using Durabond for the initial coat, then bucket mud (Gen. Purpose). An extra measure of safety can be added with Plasterweld as it acts as a bonder. Your final finish will be "softer" and not as tite as a real plaster coat.A great place for Information, Comraderie, and a sucker punch.
Remodeling Contractor just outside the Glass City.
Quittin' Time
You might want to do a search here for "DMix". It's the cat's meow for what you're describing...
PaulB
Make sure wall is primed. mix 1 POP with 3 JC slowly. Add water to make it a skimming consistancy. Trowel it on thin, when it starts to set (5-10 min) brush spatter with water and go over again with a wet trowel. Use only as much as you can work with in 15 min, and if you want to retard set a bit, throw in a capful of white vinegar. No bonders needed, yes scuff & scarify wall. It goes pretty fast once you get the hang of it.
Voila.
If the client wants everything the way it originally was then the house should have the sand finish plaster as you see. 1910 puts it into the Craftsman era, and they often did plaster walls with a rougher 'brown coat' type of finish. It might be easier than trying to get everything totally smooth. Personally I like that type of wall finish.
yeah, most of the rooms have that rougher type of finish . But the bathrooms and the kitchen are all smooth . Well , they were smooth , now Lots of settling cracks.
Go Angels
I looked up that plaster weld stuff on-line . sounds like the ticket for sure ... the only problem is the 2 hour drive to find the closest dealer to me , but oh well.
thanks all for the advise.
Plaster Weld creates a chemical bond between old plaster and new plaster.It does NOT have an effective purpose when topcoated with joint compound - redimix or setting type. See, joint compound has a different chemical makeup than plaster. Simply put: Joint Compound and Plaster are very different materials in everyway.Plaster Weld has no beneficial effect unless you are using plaster.The above info is from USG and Larsen Products - not "The World According to Frankie."As a novice, you should skimcoat the wall with an all-purpose ready mix joint compound, sold in 5 gal. buckets. It is easy to work with. Trowel it on or use a knife. Thin coats dry faster and are easier to apply than heavy coats.Frankie
There he goes—one of God's own prototypes—a high powered mutant of some kind never even considered for mass production. Too weird to live and too rare to die.
—Hunter S. Thompson
from Fear And Loathing In Las Vegas
Thanks frankie, this is what I read as well. Plasterweld/JC = no use together. I will opt to skim with JC since I'm pretty experienced with it. My main concern is whether it would stick or not, but why not?
j
If a wall or ceiling is porous and dry, compound will adhere. The browncoat you have, provided there is no residual glue from the wallpaper, will be a fine base for the compound to adhere.If wall is NOT porous, the compound will have nothing to grab on to. You must prime with an alkyd (oil) based primer. Then compound. Alkyd primer has the proper tooth and bonding characteristics for compound to adhere properly.Yes, there are other ways, but this is a right way. You will not have any problems with it. Do it right - do it once.BTW - After skimming with compound you must prime with and alkyd (oil) based primer prior to finish painting.Frankie
There he goes—one of God's own prototypes—a high powered mutant of some kind never even considered for mass production. Too weird to live and too rare to die.
—Hunter S. Thompson
from Fear And Loathing In Las Vegas
what is this "D-mix" that everyone is talking about.
It is a combination of General Purpose mud, made runny by adding latex drywall primer instead of water, and a bit of plaster of paris for a faster set... however, in doing it myself I'm not sure that the POP is needed as you are working the material long after the POP set time, so I'm not sure it actually has a purpose as an ingredient.
Nice thing is that it works like mud, but gives a final primed finish that can be painted. I think the latex gives a little extra flexibility too to prevent cracking.Rebuilding my home in Cypress, CA
Also a CRX fanatic!
I could do a search for you, but it is an important exercise for you to learn.At the top of the left column, above "Show Discussions...", there is a choice to "Post New" and "Advanced Search."Click on "Advanced Search" and type "D-Mix" into the search box. Click Search and wait, about a minute.Frankie
There he goes—one of God's own prototypes—a high powered mutant of some kind never even considered for mass production. Too weird to live and too rare to die.
—Hunter S. Thompson
from Fear And Loathing In Las Vegas
right on ,thanks.
Frankie,
Is there a particular reason you need to prime with an oil primer if a wall has been
skim coated with JC. I just finished skim coating the entire master
bedroom/bath in my house and in the past I have just used a PVA primer (water
based). I've never had a problem before....but I sure would hate to have one this
time.
Dan
pghdan,I haven't had a problem with adhesion using a latex primer either. When there is stain from water damage however - we prime with KILZ oil base. I HAVEN'T had success with latex KILZ covering stains; in fact, I wasted a lot of time once trying to make latex KILZ work on a "stapled up" tile "breakfast nook" ceiling a customer didn't want to replace. (It says if it doesn't cover the first coat, wait 24 hours and recoat - I waited and it didn't cover)One time I skimmed a whole 1 1/2 story house (walls and ceilings) that had a variety of homeowner efforts at "sand finish" cover ups. That's a good one to have in your rear view mirror and floor it. Fz
Latex or PVA primer floats on compound. They are fine for sheetrocked walls which are only taped, as they bond with/ soak in the paper face. However, neither soaks into compound. That's just the way it is. Compound dust further inhibits proper adhesion.Alkyd (oil) based primer does soak into the compound and therefore acheives excellent adhesion. Doesn't really even matter if the walls are dusty or not. It will bond.You can get lucky using latex or PVA primers, but not always. To me, it isn't worth the risk. The Benjamin Moore tech dept agrees. They will specifically state that alkyd primer is the proper primer AND latex or PVE primers are not.You and others can do as you wish with no arguement from me.Frankie
There he goes—one of God's own prototypes—a high powered mutant of some kind never even considered for mass production. Too weird to live and too rare to die.
—Hunter S. Thompson
from Fear And Loathing In Las Vegas
There are other bonding agents besides PlasterWeld. Some are applied to the wall and some are mixed into plaster. Acryl60 is one of the later.In general, if the surface is hard you will need a bonding agent to insure that the plaster adhers properly. This includes the "good" side of drywall, paint, etc.A building supply store that sells molding plaster, finish lime, etc should have the appropriate bonding agents to go with it.Regardless of what you put on, be sure to get the wallpaper paste off. Hot water and some white vinegar will generally do the trick. Spray or sponge it on, let it sit, and either scrap it off or scrub it off with a non-woven pad.I'm not saying joint compound won't work, but it will not be as hard as plaster. If you can learn to work with real plaster you will be several steps ahead of your competition.
COCTEAU3,
I have successfully skimmed walls like you describe with USG "all purpose" (also LeFarge "all purpose"). It's a lot of work, but a fan system we came up with made it a lot easier (see attachment). Of course this depends on several factors (time of year, air intake, etc).
With this fan hooked over the window we were able to use the random orbital sanders with 220 - without dust going into the house. Not to insult you but figure on 3 coats and use a bare bulb with the last.
I haven't had any problem with the all purpose sticking.
We have had some problems with "hot spots" (chemical reaction discussed on this forum several times that causes gas bubbles). For filling these after wall is otherwise finished and primed with "USG First Coat" (or equivalent):
Using a good silicone-latex caulk, damp sponge, and a 2 1/2 inch flex knife: swipe a 6 x 6 in area with the damp sponge. Fill and totally strike off caulk with the knife.
(The swipe with the damp sponge allows a complete strike off of any caulk that is on the surface - since sanding the caulk doesn't work.)
The problem I see with using the "setting mud" is that even though it is "set" the moisture still has to be removed before anything additional can be done, so I don't see any advantage. I could be wrong. I haven't used any durabond, etc for many years.
Fz
We have had some problems with "hot spots" (chemical reaction discussed on this forum several times that causes gas bubbles). For filling these after wall is otherwise finished and primed with "USG First Coat" (or equivalent):
What causes them? I don't recall reading about it here, but if you could point me to a thread (or subject), I would apreciate it.
The problem I see with using the "setting mud" is that even though it is "set" the moisture still has to be removed before anything additional can be done, so I don't see any advantage.
I use the setting type a lot, but I'm usually just doing small repairs. The advantage is that you can apply multiple coats in 1 day. Sometimes, it will dry enough in the same day to finish the job.
-Don
DonCanDo,I will give it a try on the "hot spots"- that's been over 2 years ago we had a discussion and they were bringing in previous discussions. I haven't always had good luck with prospero searches. What I am referring to as "hot spots" is anything that ends up as little craters - it looks like a bad case of healed acne. I understood from the discussion we had (back then) that there were several things that could cause the symptom (little craters). Anything that could cause gas as a reaction would be one possible cause (different ph of materials mined and used for plaster).Air in the mix from "overly vigorous mixing" was another possibility given - I got this from calling USG.Another bet was a reaction to residue from aluminum oxide from sandpaper.I'm sending a pic of it.Fz
Ah, yes. I've seen that before and even made a few myself. In my case, I think I created them by using too much water when sponging off the joint compound. I rarely wet sand anymore (except maybe in a closet in the basement) and when I do, it's with a fairly dry rag.
-Don
While you are at it, are your outside walls insulated? If not, go ahead and drill holes and blow some in now. Since you will be refinishing the walls, go ahead and insulate! Otherwise a couple of years from now you'll be complaining about having to drill holes in that wall you just finished, and wondering where that paint is at. Kill two birds with one stone!
I'll get off my soapbox now.
Use joint compound but make sure you REMOVE ALL THE WALLPAPER PASTE first. Wash the walls down with Dirtex or other NON SUDSING cleaner. I like to use a medium coarse (maroon color) 3M pad. Change the water frequently. And finish wash with clean water and a sponge. The deep stuff you can fill with Durabond 90 setting compound. Its diffcult to sand so I dont like to use it as a finish or top coat.
There really isnt much to worry about regarding adhesion if the surface is prep'd correctly. The skim coat you are putting up isn't too deep. For your finish coat put some pressure on the applicator (wall knife or trowel) and you would be surprised how smooth Joint Compund can feel.
[Recovering house painter]
Parkinson's Law: 'Work expands so as to fill the time available for its completion.'