Skim Coat

How To Prepare A Rough Plaster Surface For Wallpaper: Liner Or Skim Coat

Want to know if you can skim coat! - let´s call on the years of experience of Edwin Brown, a man who really knows his surfaces. 

"Have you ever been stopped in your wallpapering plans by a heavily textured wall that would benefit from a good skim coating?

The question naturally arises: How can I smooth out this old wall so my paper will look nice after it goes on?

Your local wallpaper hanger will tell you that he can glue a "liner" over the rough surface to smooth things out a bit before he puts on the paper.

The paperhangers I know are not always keen on this option. While it will earn them extra money, it still does not give the ideal smooth surface to paper over. This is especially true for papers with delicate designs and lots of "open space" in the pattern.

So, what do you do?

One of the guys I know who hangs paper for a living will skim coat the rough areas with drywall joint compound. He sands out the defects and puts on a good primer, then does the paper.

But Michael really doesn't like skim coating. Not that he can't do it okay. He would just rather be doing something else. He often calls me to skim coat for him. Something that I don't mind doing at all, fortunately for both of us.

But, at the same time, this is a do-able project for the do it yourself homeowner.

Skim Coat Guide

Here are some guidelines to make it easier for you if you decide to go this route.

The first key point is, you need a sound clean surface. This means you must remove all loose or scaling material, and any thing - dirt, grease, etc. - that might interfere with good adhesion of your skim coat.

If the scaling material is due to water damage, you want to be sure the water intrusion is no longer a problem.

After you have scraped off the loose stuff, and maybe wire brushed the area, you should wipe down the affected area with a damp sponge to get rid of any remaining dust.

Let this dry, then paint on an quick drying oil based stain killer, like Zinser, Z-Prime or Kilz.

For dirt and grease, soap and water or a TSP (trisodium phosphate) solution will take it off. Just be sure to clean rinse well afterwards to remove all residues.

Now you are ready for the skim coat

The simplest choice of mud would be an all-purpose joint compound. This will stick well to a prepared surface and is easy to handle (and sand later). You will be applying several coats.

A systematic approach works best. The method I like is to start at the top of the wall and work across and down. I start with all horizontal strokes for the first complete coat.

After this dries, usually within 24 hours or less, I go over it again, this time with vertical strokes, filling in the ripples created by the first coat.

It usually takes two vertical coats at least to get the smoothness I want.

You may have to do some sanding between coats, just to get rid of lines formed by the edge of your mud knife. And the final sanding should be done carefully.

The abrasive coated sanding sponges work really well on dried mud. A medium grit and a light touch - that's your ticket."

For a more complete discussion of doing a skim coat, check out: Skim Coat Solutions

About the Author
Edwin Brown is a licensed and bonded plaster repair and renovation specialist with 35+ years experience. He works on the west coast of the USA.


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