Gilles' Outlet

August 22, 2006

Skim Coating a ceiling

Filed under: House Remodelling — Gilles @ 5:23 pm

In a previous entry, I explained how I removed the popcorn ceiling. A more detailled inspection revealed that it was not as flat as I first thought. Not too bad, but not as flat. Well, since I am detail oriented, I decided to bite the bullet and skim coat my ceiling before painting it.
I started by washing the ceiling with a slightly wet sponge. The goal is to remove dust and other material which can prevent the coat to stick to the wallboard, not to saturate the board with water. It should be wet anough so it captures dust and it should dry almost immediately after you remove the sponge. I thinned some all purpose joint compound so it had the consistency of mayonaise and can eb easily levelled with a knife for a great finish. Using a 10” taping knife, I spread the "mud" on the ceiling.

I made sure to always apply the mud in the same direction (for me, it was parallel to the window), avoid coming back to an area after levelling it with the knife. As the mud dries, touching it with a tool makes it look worse than it was and increases the sanding time. Also, keep in mind that tool marks are inevitable: do not try to hard to remove them. They’ll go away during sanding. The picture below clearly shows the uncoated region (yellowish) and the coated region (greyish):

Once you have finished coating the ceiling, let it dry for at least 24 hours. Take a pole sander and erase all tool marks. Inspect the whole area and patch things you did not quite nail in the first place then sand again the repaired areas.

When you are all done and the ceiling is flat, you can go ahead and apply two coats of sealer / primer and then paint. Two coats of primer greatly reduce the porosity of the surface and allow for a clean paint finish.

Alert readers have certainly noticed that I applied only one layer of mud on the ceiling. My ceiling needed coating but it was not hat bad so I got away with one layer applied with care. Usually, skim coating is done in two layers: one "vertical" layer, one day to dry, one "horizontal" layer to fill in low areas left during the first pass and one sanding pass.

 I have a few spots to fix and some sanding to do. Hopefully I’ll be able to paint in the next weeks.



  1. Thank you for your insight via experience—I now have a better idea of what I should do to repair my bathroom ceiling. Kids failed to turn on the fan while showering & the ceiling began to peel. The paint on the exterior wall also began to peel. I think I should skim coat both the ceiling & wall to the exterior of the house and repaint – what do you think?

    Comment by a kay — January 15, 2011 @ 1:37 pm

    • Kay, I am sorry to hear about paint peeling. Skim coating typically involves joint compound which is not adequate for exterior use so I would not skim coat an exteriro wall exposed to the elements.

      Comment by Gilles — April 30, 2011 @ 8:50 am

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