How To: Paint a Wood Window Sash

Old WindowAfter all the hard work is done restoring a wood window there is one final step, painting your window sash. Painting a window is by far the most important part of the process because it protects all the work underneath. It keeps sun, rain, dirt, insects, air and anything else from harming your window.

Without paint, glazing putty is no good after only a couple months, the sun’s UV rays begin breaking down the wood fibers of the window immediately, water will cause corrosion of your glazing points.

Without paint your window will fail quickly. But you already know that you have to paint your windows, right? Maybe so, but there is a very specific way that historic windows should be painted to both protect their parts AND ensure smooth operation.

Here are my 5 rules for how to paint a wood window sash.

1. Don’t Paint the Sides

The sides of the sash that slide up and down in the jambs should be left bare. No primer and no paint. This may sound odd, but it has been in practice for well over 200 years.These areas are not seen or readily exposed to the elements so there is no cosmetic reason to paint them, but there is a more practical reason NOT to paint them. By leaving these areas bare you allow both rails (horizontal parts of the sash frame) and both stiles (vertical parts of the sash frame) to expel moisture.

How to paint wood window

Unpainted sides and bottom on old window sash

With these sections bare the entire sash is able to dry out if it should happen to get wet. Bare wood breathes much, much better than primed and painted wood.

In addition, these parts of the sash slide against the window jamb and if they are coated with paint (especially latex paint) they will stick and be extremely difficult to open and close. Leave it bare.

2. Don’t Paint the Bottom or Top

For the same reasons as above the top of the upper sash and bottom of the lower sash should not be primed or painted either. These parts are not visible when the window is closed and therefore not exposed to the elements. Again, this will aid in the window’s ability to dry out. Not much else to say about this so let’s move on.

3. Use Oil-based Primer

For the best performance use an exterior oil-based primer. I prefer Kilz Complete in my shop because it is hides very well, goes on easily and sands down nicely. The sash should be primed and lightly sanded with 220-grit paper to smooth out the surface before installing the glazing putty.

Use a brush and work the primer into the wood. Spraying on primer is fine, but be sure to work it in with a brush as you spray. Brushing ensures a better bond between the wood and primer than spraying alone.

4. Apply 2 Coats of Quality Paint

Whether you decide to go with oil-based paint or water-based doesn’t matter to me. The point is the get at least two coats of paint on the inside and outside. Don’t skimp on this paint either. Use a top-notch enamel paint. I prefer Sherwin-Williams Porch & Floor because it is an easy to work with water-based paint and since it is formulated for floors it gets very hard, very quickly.

The technique for painting your window sash is difficult to describe in a blog post so I’ve put together a short video to show you how it should be done.

Check out the video below and don’t forget that you can get more videos like this by subscribing to our YouTube channel.

5. Finishing Up

Once the windows are painted let them sit aside and cure for at least a few days. This may sound pretty elementary and I’m sure you would never try to put windows with wet paint back in, right? It’s not about the windows being dry. It’s about the paint having time to cure.

Water-based and oil-based paints can take up to 30 days to fully cure. Until that time the paint is more prone to being damaged by scuffs, knicks, and water. Don’t try to wipe down new latex paint or clean it until that 30 days has passed. Otherwise you run the risk of messing up your paint job.

Once the paint is cured enjoy the finished product by opening those windows as much as you’d like. You deserve it!

If you have more questions about the rest of the process of restoring a wood window visit my resource page How To: Repair Old Windows

 

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by Scott Sidler

I'm a historic preservationist and author. I help old house lovers understand & restore their homes so they can enjoy the history and character that surrounds them more everyday! When not working, writing or teaching about old houses I spend most of my time fixing up my own 1929 bungalow with my wife Delores and son Charley.

http://www.austinhomerestorations.com

22 comments

  1. dee on said:

    Best thing I ever did for my 1926 windows was to get storm windows. Also these old windows if kept rot-free are MUCH superior and more economical to repair that so-called double-glazed windows. Double-glazed windows are horrifically expensive and have a 100% failure rate.

  2. Jon H on said:

    How do you handle sash tracks that have been painted? Do you strip them to help with ease of raising/lowering? How about any other lubricants or waxes in the tracks? Thanks!

    • We scrape all the old paint from the jambs the prime with oil-based primer and repaint if requested. Usually I prefer to leave the jambs just primed so they don’t bind.

  3. I think folks need to hear how critical prepping the wood for repainting is to the renewed life of the window. If the old, dry paint is not completely removed, the new paint will not stick well and fail soon. Stripping paint with chemicals or steam drives moisture into the wood. It takes extra days to neutralize and dry this wet wood. Infrared heat Speedheater works by softening the paint with low heat so the paint scrapes off easily. The bare wood is ready immediately for priming and painting.

  4. tricia on said:

    Scott – great article – I am undertaking the task of redoing 1935 double hung windows & some perhaps 1960/70 wood ones on the top floor. I’m in a historic district but the house was vinyl sided before I bought it and the windows wrapped with vinyl/the old windows were left in except for a side porch window. I’ll have to paint these in place/not removing them but I am at a loss on a few things. It appears I should abandon my plan to use Zinsser 1-2-3 primer & instead use oil primer. Not cool. But I will do it if that is necessary/I am presently removing years of old glazing compound/botched paint jobs and repairing wood. There are storms on the windows as well that I have removed screen and glass wise but the alum frames aren’t coming off – in some cases, the siding overlaps them – sigh. My question is should I paint the windows (sashes) to match the horrid vinyl wrap around them or should I contrast slightly? Any help or thoughts appreciated. I wish I could afford to have this done but really don’t have the money at this time to have a pro do it & I can’t let the windows deteriorate any further. They seriously need reglazing and paint. Thank you!!

  5. Dave on said:

    Great turorial Scott. I am in the process of restoring a large bay window and have removed the center picture frame for reglazing. It is now stripped down to bare wood and I have a question about painting the interior-facing side. Should it be completely top coated prior to installing glass or will the putty that oozes out of the rabbited area interfere with the painted surface? I’d hate to wait 30 days for the interior side to dry before tackling the glass installation.

    • You’ll wanna seat the glass and wait a few days till the putty is skinned over to paint the interior. Lap the paint onto the glass about 1/16″ on the inside as well as the outside to keep the putty from failing prematurely.

  6. Dave on said:

    What are your thoughts on a push-out casement window? Should the sides, top, and bottom edges be painted or left bare? My originals were painted, but they were also damaged slightly by rot on the bottom corners.

    • We usually prime and paint all sides of casement windows since that was typically the practice for decades. I’m still doing some testing to determine what is best, but for now I haven’t had many issues with this technique.

  7. Joan on said:

    I am redoing the wood storm windows for my 1923 Craftsman bungalow. I stripped the paint, removed 90% of the glaze but decided to hand off for the rest of the removal and the reglaze. They didn’t prime before they reglazed with DAP33 compound. I am sick. The company is a reputable glass dealer in town. What do I do? I already have paid out dearly for them to do the work. Thank you.

    • Joan, though I don’t use DAP 33 I do know that the manufacturer requires wood sash to be primed with an oil-based primer prior to glazing. I would contact the company and have them redo the work correctly as per the manufacturer’s recommendations. They should have known how to properly apply the glazing putty if they took on the job.

      • Joan on said:

        Thanks Scott. I had called them before contacting you but was told they have always done it this way and have never had a problem. I also contacted their competition and was told the same thing. They don’t prime or linseed oil because of the dry time. It is a minor part of the business for both of them. They will not redo them. Lesson learned. Don’t assume that because they are the “professionals” that they are going by the book.

  8. Josh on said:

    I recently bought a craftsman house built in 1908 that has all the original windows. so I have lots of glazing to do. I want to restore this house to its original beauty and was curious about staining the interior of the sash instead of painting. I can not seem to find any information on painting the the outside but not the inside.

    • Josh, we do a lot of windows that are stained on the inside but painted on the exterior. If you are planning to fully restore the windows I recommend that instead of priming the glazing rabbets you either use shellac or Boiled Linseed Oil before glazing. That way you don’t get any primer runs onto the inside of the sash. Once it’s glazed you can prime the outside and stain and poly the inside. Also, use a spar urethane for the interior which will hold up to the UV and moisture better than regular polyurethane.

  9. katherine tarbox on said:

    Well, I’ve just managed to get my 100-year old casement window open, but I can’t get it open enough to expose the horizontal piece on the top sash (the one just under the lock) in order to scrape, prime, and paint. It looks pretty bad–peeling and flaking,etc. What can I do? thanks!

  10. Noble Larson on said:

    Scott,
    I found your video about painting sashes very helpful. One question: the video covers the exterior (i.e. glazed) side. In particular, you emphasize (as other sources do) “lapping” a thin fillet of paint from the glazing onto the window glass, to provide a seal. Makes lots of sense for the exterior. How about the interior side? There’s no glazing, and certainly fewer issues of water pentration. Is it necessary or recommended to lap paint between the wood muntin and the glass. (I’m talking old-style single glaze sashes.) Or is it ok to scrape off any paint on the interior side of the glass back to the muntin?
    Thanks!

    • Noble, yes you should still lap the paint onto the glass ever so slightly on the interior. There is a small bed of glazing putty there and to protect the sash from condensation in the winter the paint should go onto the glass about 1/16″ or so.

  11. Courtney on said:

    i just want to clarify, you prime with oil primer, and it’s okay to paint over that with latex paint? I’ve always heard the oil primer would “reject” the acrylic latex, and not create a bond.

    • Courtney, latex over oil-primer is not only ok to do but it is considered an industry “best practice” for painting wood.

  12. craig glaspell on said:

    Paint vs Stain/Varnish/Lacquer…is this just personal preference, or is it advised to paint double hung windows? my 1923 craftsman has all natural wood windows and doors, but the only PAINTED windows in the house are the double hung? I didn’t know if this was previous owners idea, or is there some reason for this?

    • On the interior, paint or varnish is just personal preference of the original owner. Might be fun to do a little digging and see if the double-hungs were originally varnished too.

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