I need help with taping plaster to drywall & prep to paint.

enduringJuly 21, 2012

Also posted in the Bathroom forum

Hi, I need information on how to tape seams between new dry wall, old unpainted plaster, & painted plaster surfaces in my bathroom remodel. I have a hole to repair too where the old vent stack went out through the ceiling. In the pictures you will see where I peeled off old latex over very old paint from the 40's or so. I wanted to clean up where the taping joints will be. I have not sanded yet but plan to do so.

In reading the other posts on this topic I think it is recommended that I sand the painted ragged edges to smooth, and all over the painted surface to rough it up. Next, wash all painted and plastered surfaces with TSP and rinse well.


1) do I prime with Gardz, before taping?

2) do I prime the new dry wall too before taping?

3) Do I prime the whole ceiling before I skim coat (if I do this)?

4) How do I handle that hole in the ceiling? (I was going to use scrapes of drywall and mesh to cover, then mud it in place.

5) I bought the low dust blue lid joint compound, will that work for taping corners and ceiling junctions?

Any help would be great!

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Scuff it up a little bit and use setting compound for the first coat(eg. easysand 20). For the big hole, I'd use a mesh patch and easysand it, too. I butter the back of those things with a little bit of mud before I set them in place, then skim some compound over them. When it's partially set, check to make sure it's not bubbling outward from the weight (if so, push it in gently). After it's hard, hit it with another coat.

    Bookmark   July 21, 2012 at 7:50PM
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Sophie Wheeler

Paint from the 40s assuredly contains lead, Do NOT do any sanding of this without understanding how to practice lead containment.

    Bookmark   July 21, 2012 at 9:19PM
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Thanks Homebound I will check out the products you mentioned. I have a mesh patch that is the size for that hole. I had been thinking to use the patch to hold a scrap of drywall in place. On one of the threads I read about easysand 20. I will pick this up.

So Hollysprings, Should I paint with Gardz and then skim coat the ceiling? I will not proceed with the sanding. I know the top coat is lead free because I put it there, but underneath is most likely lead.

I could probably do the skim coat successfully. I am somewhat good with things like that, though I have a "slap dash" side to me too. Ultimately I could put a textured skim coat up there, but I wanted smooth.

    Bookmark   July 22, 2012 at 9:41AM
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If you can work some 1x wood strips onthe back of the plaster you can use longer drywall screws tpo fasten thtem in place.

Then cut a drywall patch smaller than the hole and fasten it to the wood backing.

Setting type compound can then be used to build the patch up level and fill in the edges.

You want to make sure you have at least a 1/8 inch gap between the patch and the edges of the hole.
This allows the compound to form keys to lock it to the old plaster and the drywall backing.
Any bigger than 1/4 inch starts to be a PITA to fill.

    Bookmark   July 23, 2012 at 4:06PM
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Brickeyee, thanks for the instructions, I will follow these. I think it will work well.

I have a question for you about the 2 surfaces, one plaster, the other new sheetrock. Should I prime the old exposed, intact, plaster with Gardz to provide a surface for the plaster to successfully be taped to the new sheetrock? I read somewhere that plaster did not take well to joint compound. It might have been something about drawing the moisture out of the joint compound too quickly for proper curing of the JC. I believe that was why the Gardz was recommended on the plaster - to provide a surface for taping the two materials at the junctions.

I've read on differing post that skim coating sheetrock is not a good idea, that the joint compound is not strong enough, or something, though I did see the USG website demonstrate the use with the green lid JC. I would like to skim coat my one existing plaster wall, and the ceiling (unless the primers will even out that ragged edge between the paint and raw plaster). If I skim coated I would use the technique shown on the USG web site which involved thinning the green lidded JC to thin pancake batter constancy then rolling it on the surface.

Last, Brickeyee did you see my recent update on my floor joist post from last fall? I have linked it below. Update is the last posting. You were very helpful when you posted so thanks. I really think my DH did a fab job on the additional joisting. There are new pictures of the joist in place on the link.

Here is a link that might be useful: Adding Joist to Existing & Intact Floor

    Bookmark   July 24, 2012 at 7:30AM
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I found this thread, in my history will it work to repost?

    Bookmark   August 4, 2012 at 3:13PM
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Yippee it worked. My thread is back. I had to go into my computer's history to find this thread. I had posted to it last week or so and it never re-appeared on the GW forum.

I fixed the large hole with plastic screen type lath, fastened up into the plaster with drywall screws. I couldn't reach one edge so I wedged in a 1x.5" piece of wood lath at one end and overlayed the plastic lath, and I think the screws are pegging the plastic screening in place :) There was a lot of technique getting that piece of plastic screening up there!

Then I took Easysand 20 and filled the screening, it was ugly:

After it dried for several days I took my "California Patch" and slathered a bunch more Easysand 20 on it and wedged it in place. It stayed! It is drying now. As I was trimming away some of the extra Easysand I inadvertently scrapped away some of the sheetrock paper, not the full thickness though. It will need to be gone over with another thin coat of mud, either Easysand or my pre mixed green lidded joint compound. It will need to dry for a long time:

I took that Easysand 20 and filled the gap along the entire ceiling periphery. After several hours, I took my 5-in-1 tool and shaved it flush with the existing plaster ceiling and made sure everything looked square. The product was still damp and easily shaved.

When all of this dries I will tape up the corners and ceiling junctions using the green lid premix joint compound and a webbed, creased, tape I found. It was sort of expensive, but I only have right angles on this job and I figured it would help make the angles cleaner.

Thanks for everyones input. It was very helpful. Now I just hope this works out ok as I have some thick layers up there.

    Bookmark   August 4, 2012 at 3:50PM
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Thickness with setting compounds des not matter all that much 9if at all).

I have used them to fill the space of plaster grounds (often a full inch thick and about 2 inches wide).

Setting compound barely shrinks if you use the minimum water needed to mix it up.
it should be about as thick as peanut butter (smooth with no lumps please).

About the only thing you missed was misting water on the edges of the old plaster to prevent it from drying out the setting compound before it sets up properly.

If the setting compound is hard at the edges touching the plaster it is fine.

    Bookmark   August 4, 2012 at 4:06PM
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Thanks Brickeyee, I wanted you to see this. Good to hear that the thickness doesn't matter. I got the consistency right, using your peanut butter analogy. It was tough getting that first stage of compound up there. It kept falling out. So I resorted to my hands, smushing it into place. That was the secret. Hey, did you ever see my completed joist installation for my bathroom floor? I just posted an update to that old thread from last fall.

    Bookmark   August 4, 2012 at 4:22PM
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