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Old 06-29-2009, 01:16 AM   #1
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Smoothing Joints Between Sheetrock and Plaster Without Sanding

I recently had a leak in my roof that is going to force me to replace part of my Kitchen ceiling. My house is sixty-eight years old and has the original plaster ceilings. When I square off the section I want to replace, how do I match the depth of the old ceiling to the new sheet rock and does anyone have a way of smoothing the joint compound without sanding. The leak happened in my kitchen and I don't feel like telling my wife that she has to empty all the cabinets and have a major clean-up job after I'm done. Any suggestions out their or am I being overly optimistic that someone has a method to reduce dust that I haven't heard about.


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Old 06-29-2009, 02:29 AM   #2
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The big variable is how thick is the plaster and is the lath?
  • buttonboard ( plasterboard)
  • Wire mesh
  • wood lath
The other variable is how big is the area to be replaced. Is it half of the total area? Is it 10%

And finally is the area to be replaced in the center? against a wall? in the corner?

these are all important questions to get a workable solution.
If possible please post a pic


& Stay Safe
.....Bob Lavery
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Old 06-29-2009, 07:53 AM   #3
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Cut the plaster back to the nearest joists. Install the appropriate size drywall and shim as necessary to match ceiling. Its o.k. if it is a little shallow (1/32"-1/16") as you can fill in with joint compound. Use plaster repair screws ( and re secure the surrounding plaster to the lath. Tape and finish the joints. Its probably going to take three coats to spread the mud out far enough (12" to 16") on this kind of patch job. If you pull your top coat really tight you may be able to avoid sanding but I doubt it. I would recomend putting up 3mil. plastic sheathing in the area to be sanded usin a zipwall type system to control dust. To save money you can make a cheap zipwall system with extending type sanding poles that will work fine for a project of this size. If this is to much for you you can wet sand (literally use a wet sponge to smooth the dry mud out) but this will not produce as smooth a finish. Another option is to use a disc sander attatched to a vacume (available by porter cable) but these are pricey ($500 to $1200). I have also seen small hand sanders (big box stores) that attatch to a shop vac that you use with a sanding screen. I have not tried these myself and the feedback I have gotten back from others who have is it's so so.
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Old 06-29-2009, 09:02 AM   #4
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I just wanted to give an addendum to ARI's link for the washers Excellent product and they are used primarily for securing plaster that has fallen and needs to be snugged up as well. So if you have some plaster around the house that is starting to crack and come loose you can re secure the plaster back to its substrate and then skim over the top. This is so that they spread load the pressure and hold the plaster in place without shattering it into little pieces.

Also, I will ask you do you have a homeowners policy? If this is a significant project and you don't feel that you have the expertise or the tools to accomplish the task then I would contact your insurance company and file a claim. They will then pay you to have the repairs made. You will have to pay your deductible however if you are going to be buying materials and renting equipment and putting up with the headache of making the repairs on evenings, weekends or even taking days off of work it might be well worth the $500 or whatever your deductible may be.

My biggest concern at this point is that you prevent creating a serious health issue in removing the plaster and subsequently at the same time removing the paint. Because of the age of the building, I would be willing to wager significant money that the paint you will have to remove will contain lead especially if any of the paint on your walls was produced before 1978 and some even during.

Before you do any plaster patching, I urge you to rid the rooms of any residual lead. If you try to vacuum up chips or dust, you must use a special HEPA filter-equipped vacuum cleaner. Some rental stores rent these. Change and wash the filter regularly and dispose of the wash water down a toilet. Mop the floors and wash down walls making sure to change the wash water regularly and dispose of the contaminated water down a toilet. Obtain all approved cleaning procedures and from the EPA's website:

I think you can successfully patch the plaster if you have some patience and a fair amount of hand-eye coordination. To obtain professional results you will need to practice and use the correct products. Many old plaster patching jobs fail because people use the wrong materials for the job.

Do not use the common drywall joint compounds you often find in home
centers. These products are only meant to be used with paper-faced drywall. They bond poorly to traditional plaster. Plaster patching must be done with patching plaster and sometimes plaster of Paris for the best results. You can achieve moderate success with setting-type joint compounds and these might be a good product to use to practice your repair techniques.

Setting-type compounds are powders that mix with water. The water starts a chemical reaction that causes invisible crystals to begin growing. These crystals interlock within the coarse open plaster to create a strong bond. The advantage to using this material is that it is often sandable. If you make a finishing mistake, you can sand down any excess material.

Traditional patching plaster and plaster of Paris are not sandable. Before applying any product to the walls, they must be clean and free of any dirt, grime or grease. All loose plaster must be removed and all cracks should be enlarged (called back checking) so that the top of the crack is at least one-quarter inch wide. If at all possible, try to make the bottom of the cracks wider than the top. This will take extra work, but the patching compound will interlock into the old plaster like a dovetail joint once it hardens. Slightly dampen the areas to be patched with water just before applying any patching compound to increase its adhesion as the surrounding dry materials will suck to the moisture from the material you are patching with and causes it to set too quickly resulting in improper curing times.

The trick to patching plaster is to start with small holes that are no bigger than two inches in diameter. If the hole is deeper than one-half inch, then only fill the hole halfway with patching material. The patching material may harden within several hours and then you can mix new material to finish the job.

Use regular drywall finish tools to work with the patching materials. I prefer to use different knives, my favorites being five-inch, ten-inch and twelve-inch flexible broad knives. These tools held at a 30 degree angle to the wall allow you to spread the patching compounds much like you spread icing on a cake.

Both the setting type compounds and the patching plasters can be finished with a sponge as they harden. Professional plasterers will often use a small amount of water on their trowels to make the setting plaster slick as a piece of glass however it takes great skill to perfect this method. You can try to do this as the compounds set, but you have to time it just right and may eliminate your need to sand if you opt to tackle this project yourself.

The best way to practice is to mix some of the patching plaster and use it to fill a small hole that might be hidden behind a piece of furniture once the remodeling is complete. Use your drywall knives to apply the compound and get it as smooth as possible with little or no excess on the wall. Make sure you use a knife whose blade is longer than the hole/ crack is wide. With the blade spanning the hole/ crack, make repeated light strokes over the wet patching compound until no excess material collects on the knife blade. If you press too hard, you might create a slight depression in the patched area.

Use the sponge to wipe any excess patching compound off the adjacent, sound plaster. As the patching compound gets quite hard, gently stroke it with a damp sponge to make it smooth.

Good luck and like I said if you have a homeowners policy you may want to contact your agent but if you don't opt to do so then I hope some of the info I and others such as ARI and PaliBob gave help.

Good luck and be safe
James D. Van Raden
Owner, Paragon Renovations Moorhead, MN/ Fargo, ND
"Committed to providing the finest renovation services available"
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Old 06-29-2009, 11:28 AM   #5
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The leak is above an exterior door that was caused by a gutter that could not handle the recent amount or rain that had come down in the area this year. In fact, I haven't gotten up there to probe yet but some of the wall above the door may have to be repalaced too. I'm going to get up into the ceiling tonight or tomorrow and let you know what I find. My house was built by the original owners (husband and wife) by themselves in December 1941. In fact the building materials were delivered to the site on December 6, 1941 and on December 8, 1941, the husband went down and received a six month deferrment so that he could finish the house for his wife before he fought in WWII. Whenever I do something in the house, it is never constructed as expected. I am reluctent to tell you what I'm going to find when I take down the ceiling. By the way, I estimate that I have to replace a 4 X 12 section
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Old 06-30-2009, 08:01 AM   #6
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Mike ,I am sorry to tell you but if you want to get a smooth finish your going to make a mess no matter what you do ,your even going to get dust just putting in the screws,The best you could do would be to get some plastic and tape the area off before you start to keep the dust and mess to a min.and in a confined area.At least the wife will see you made the effort to not get dust everywhere and that will minimize the butt chewing.The wet sanding works fairly well but most only use it to finish .the sanders to vac hookups work but ya still get dust so just try to keep it in one area and good luck
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Old 06-30-2009, 07:42 PM   #7
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Thanks, the wife really isn't that bad. It's taking all the crap out of the cabinets and cleaning it that I really dislike. Oh well, looks like a great 4th of July weekend


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