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Help with plaster walls

badgers19's picture

Hopefully I'm in the right forum, apologies in advance if not.  So, I recently removed a wall that seperated the dining room and kitchen.  I now have one big kitchen.  The dining room walls and ceiling are a rough swirl pattern of plaster and I think sand in it.  The kitchen walls and ceiling are smooth plaster.  The plaster in both rooms is approx. 3/4" thick plus the backing board.  Kitchen size is about 18'x15' and the old dining room is about 12'x15'.  I have to patch where I removed the ceiling and the bulk heads so I'm not sure what material to patch with (drywall, blueboard, ...)???

I would like to make the dining room walls smooth to match the kitchen but I'm not sure if I can sand it or what method to use, and of course there is paint on the walls.

For the ceiling I would like to try and match the rough finish of the dining room, but again I don't know if I can put plaster over paint or what the best approach would be.

Bottom line would be all walls smooth and the ceiling rough.

Any thoughts (other than I'm crazy) would be appreciated

Thanks in Advance!!!!!!!

Basically, if you want to (post #215436, reply #1 of 7)

Basically, if you want to exactly match the old finishes, and you want the surfaces to hold up well and not crack or spall, you need to either hire a pro or spend a lot of time studying up.

But you can approximate the finish with drywall (layered as needed) and a skim coat.  It will crack, though.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Thanks Dan! (post #215436, reply #2 of 7)

Thanks Dan!

For filling the space left by (post #215436, reply #3 of 7)

For filling the space left by the removed wall:

  • Clean, vacuum, and then wash the edges of the existing plaster.  Spray bottle of water, soft brush, and some rags will do for washing. Idea is to get a clean surface, no dust, for the repair to bond to.
  • Screw on 1 or two layers of dryway in the opening to act as backer. Leave at least 1/2 inch for the next step.
  • Use a setting type compound to fill in opening. Work the compound into the edges for the existing plaster for a good bond.  I use Durabond 90 for this.  Depending on thickness, you may need 2 or 3 coats to fill.  Leave the final coat a little below the finish surface.
  • Use a sandable compound for the final coat to bring surface even with the existing plaster.

As to getting smooth walls: 

  • You can't sand plaster. 
  • You can chip it off with a wide chisel in an impact gun.  Skim coat with Durabond or plaster to get a smooth surface, followed by a primer-surfacer for final coat.      -> HUGE mess + dust everywhere.
  • furring strips and new drywall may be easiest and faster.

Matching the rough ceilings?  Practice...


You are not crazy, maybe a little ambitious...

Good Luck.  Show us some before and after pictures.

LOL, Thanks Catman!!  Thats (post #215436, reply #4 of 7)

LOL, Thanks Catman!!  Thats some good info, what I was looking for :).  I think I'll skip the smooth and go swirl coat all around.

I think I can help (post #215436, reply #5 of 7)

Sorry to have missed this. I think I can help. I am going to attempt to attach 3 photos to help you visualize what I am talking about. First, build up your repair areas with substrate (drywall or cement backer board) so that they are within 1/8-1/4" of the finish plane. You will be applying what I call "pseudo-plaster" in three coats: scratch, intermediate and finish coat. Sometimes I can do it in two coats, depending on the texture. The ingredients for pseudo-plaster are: USG Green taping compount (scratch coat), USG Blue (easy sand) compound for the intermediate and fininsh coats, Masons Sand and Silica Sand. 

BASE COAT: 2 parts USG green taping compound and 1 part masons sand. Proportions are aprox. Mix to a trowel-able consistency and apply with a drywall knife. I prefer the 6" knife along edges and the 9" or 12" knife in the field. A drywall hawk holds the mix. Here, the masons sand sets the depth of the application. Apply at a30-40 degree angle and clean off at a low pitch angle. Let dry. You will see heavy streaks in the base coat. Don't worry. I always use USG green bucket taping compound because it acts like a glue. After the coat has dried, "knock down" any high spots.

INTERMEDIATE COAT: 2 parts USG Blue (lite) taping compound and 1 part Silica sand. Apply as before. This time, go over the applied coat with a damp (almost dry) sponge and smooth out trowel marks. You need to clean the sponge often, because it tends to pull off the applied material. If sponging poses a problem, don't do it. Let the coat dry. By now there should be relatively few streaks in the applied coat. At this point you can do a light sanding. Sanding causes the silica to drop to the floor as the coat smoothes out. Don't sand too much.

FINAL COAT: 3 parts USG Blue (lite) and one part silica sand. Peanut butter consistency. Apply this in a very thin coat of 1/16" or less. Allow it to partially dry before you texture with a sponge. For a semi-smooth to an almost completely smooth finish, allow the coat to dry. Then sand out the silica until you have achieved the smoothness desired.

My process requires a strong wrist and some practice. Do this on scrap drywall. The total thickness of the 3 coats should not exceed 1/4". It helps to have a few bottles of beer on hand :)

Mel Fros

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One more thing (post #215436, reply #6 of 7)

One more thing. You will need to apply a mesh-type tape to areas where repair and existing surfaces interface. Generally I do this after the scratch coat has been applied. In some cases, for intances where I need a perfect match of texture, the final coat is applied over the whole ceiling or wall. With skill and spit you can make a repair that is virtually indistinguishable from the existing texture...but it takes skill, patience, and years of practice. Don't let that stop you from trying, for even if the textures don't match, you can always follow up with another coat. As I said, keep bottles of beer handy :)

Mel Fros

More show-and-tell photos (post #215436, reply #7 of 7)

The first photo shows drywall being used to fill in around a newly-framed door. Notice that plaster lath is visible in some spots. Not to worry. You can create a rock-hard filler materials by combining USG (green) taping compound, masons sand and thinset (used in laying tiles). Thinset acts like a glue and provides the apropriate elasticity needed to do a nice job. Lightly sponge the existing lath and plaster before applying this base coat. 

The next photo shows a thin layer of self-adhering mesh applied over the repair area and the existing plaster. This will be followed by an intermediate and a final coat of pseudo-plaster.

The third photo shows a challenging repair area. The existing plaster ceiling interfaces with a new (drywall) wall. The curvature has to match the rest of the room. I use a large plastic sheet to make a template of the curve. I will use this template to guide the laying of scratch, intermediate, and finish coats. In this particular case I opt to use wide metal corner bead (typically used for true plaster applications), to bridge the gap between wall and ceiling. My first scratch coat is a mixture of USG green, thinset, masons sand and water. The consistency of the mix is "stiff". After the scratch coat dries, the entire wall and the entire ceiling (previously primed) are covered with 24" wide rolls of self-adhereing mesh. Now the intermediate coat is applied. I use 12" and 6" mesh as I apply further intermediate coats of pseudo-plaster until the curve is "just so". Then the final coat is applied across the whole field. Admittedly, this is not a task for a rookie: it requires a good eye, patience, good sponging techniques, and steady hands. 

For the DIY-er I suggest you practice on scrap sheets of drywall. Focus you attention of making a beautiful repair job. so that interfacing planes are the same (no bulges, no depressions). Then focus on texture (swirl etc).

Mel Fros

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