Refinishing Wood Windows – Making Sure Your Work Lasts

Every year I refinish the insides of many wood windows. The main problems encountered are water from condensation and a wood finish that has turned to powder due to UV exposure. Proper preparation and the choice of wood finish are critical in order to have lasting results.

However, carefully refinishing wood window frames the first time will prevent many problems in the future. Make sure that the window frame is intact and the glazing does not need to be replaced. Then, using the right type of varnish will protect the wood.

Fix the Exterior Frame First

Applying glazing putty to wood windows.
The condition of the exterior glazing, frame and caulking directly affects the interior side. Make sure all of these areas are in good condition. Glazing is the putty that goes between the glass and the frame to hold the glass in place. If it has any cracks or is crumbling, it should be replaced. Now is a good time to replace any glass with pits or cracks.

Look around the outside of your house for any other places where water might be able to enter your windows and erode the finish. If there are holes, caulk them, as needed. This will prevent water from getting under the windows frame and either discoloring or even warping the wood.

Finally make sure the exterior paint or finish is in good condition and doing its job. If needed, repaint the exterior of the window before refinishing the inside. This way the hard work you do inside won’t degrade soon after refinishing your wood windows.

Preparing Wood Windows for Refinishing

What needs to be done depends on what type of finish is on the window now, its condition and what finish you want on the window sashes and frame. If possible remove the sashes from the frame. Before beginning anything clean the glass and protect it from scratches with a layer of safe release blue painters tape, 1-1/2—2 inches wide, up to the wood you will be working on.

Varnish in overall good shape, faded sheen and some light flaking. – This is the easiest to deal with, basically maintenance. First clean the window to remove any dust or residue. A vacuum and duster brush will work. Cleaning can be as simple as fresh water and a clean rag. If needed use a mild dish soap and warm water.

All loose or flaking finish needs to be removed. A light sanding of all surfaces using a medium-fine sanding sponge should remove any flaking finish as well embedded dust. Remove the sanding dust before proceeding.

At this point you can go ahead and apply two coats of varnish, if there isn’t any wood stain used or if it is in perfect shape. Most likely a little stain will be needed. If you know the color go head and brush on some wood stain, allow it to sit on the surface for a few minutes and wipe of the excess with a clean rag. Allow the stain to dry overnight and then apply two coats of a clear finish.

Varnish peeling, water stains and the wood stain in bad shape. – This is more than just maintenance. Refinishing wood windows in bad shape is true refinishing. In this case you have some choices to make.

  • Sand down to raw wood. Doable but depends on the window construction or type.
  • Strip off the current finish. A better choice as it is faster than sanding alone and requires less effort overall.
  • Sand off whatever is loose, prime and paint. This is the option most take. It is fast and cheaper.


All of these choices involve creating dust and possibly exposing yourself to toxic chemicals. The same applies if you want to completely strip off paint and stain and finish your sashes, frame and casing trim. Make sure to test for lead paint and protect all surrounding surfaces.

Tips for Refinishing Wood Windows

  • When you are all done sanding, chemically stripping and sealing do one more thing; Apply a small bead of clear paintable caulking where the glass meats the wood. This will seal the wood from moisture caused by condensation. This is the #1 cause of problems with old wood windows.
  • If you can remove the sashes from the frame do it, as mentioned, and make sure to seal all sides of the sashes.
  • Wax the wood slides after refinishing, the slides are the surfaces the window slides on. Use any paste furniture wax. This will help prevent sticking.

Using the Right Kind of Varnish

Windows face two challenges: rain and shine. Rain can do the most immediate damage by causing water damage. Glazing and caulking should help prevent water from reaching the inside of your house.

However sunshine can also cause varnish to cloud up and begin to peel, as well. Marine or spar varnish works to prevent that and can hold up to both sunshine and moisture. As a result, it is commonly used for doors but can be used for any wood that might encounter weather. A couple coats will protect the wood from the elements and make sure that it looks beautiful.

Refinishing wood windows presents many challenges that are special to the fact that your windows are exposed to sun and water. Properly sealing the joints where glass and wood meet and corners will help to prevent water damage. You also want to be sure you use a varnish that won’t be damaged by sunlight. By focusing on proper sealing and the right varnish, your work will last much longer.

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  1. michael

    What should I use on the sides where the window slides up and down to reduce friction

  2. Vicky

    Hi I have windows in really bad state, they have flaky patchy stain. I have sanded one down and re-stained but it’s awful and patchy. Please could anyone recommend a chemical stripper to get all the stain off and start from scratch? Any advice welcome. Thanks

    • Paint stripper will work to a point but lifting all stain from the wood won’t happen with a paint stripper alone. Use a strong solvent based stripper first then rinse the wood surface with paint thinner or stronger solvent. After this dries sand the surface to remove whatever is left.

      Experiment a little before committing to the entire window. Best to screw up a small area than the entire project.

  3. Kim

    I need a bit of professional advice here 🙂 I have a set of 100 year old windows that will be used for both interior and exterior event decorations. I have stripped them all down, removed the old glazing and installed new points where needed. Now I’m at a loss finding a product to reglaze with that can be stained not painted. Is the modern reglazing product stainable and I’m just missing something in all of the you tube videos etc? Or is there a product I should be using instead? Thanks so much for all of your help!!!

    • I’m not aware of a stainable window glazing putty but it can be tinted to match the surrounding wood. For oil base window glaze mix in, or knead, small amounts of oil base paint. You will need to mix in some whiting from time to time to get back the putty consistency.

  4. Susan M Schottin

    Then after tinting and applying the glazing, can Helmsman Urethane be brushed on it, and should the urethane cover a sixteenth inch beyond the glazing onto the glass? How many coats? I want to stain and poly both sides of the window (I have metal storms.)

    • Yes, the glazing goes onto the glass, at an angle to shed water. You will need to play with the technique a bit to get the hang of it. Yes, Helmsman can be brushed on the glazing after it dries a bit (day or two).

      2 coats of varnish should be applied with 24 hours or so dry time between coats. The second coat can be applied sooner if you have good warm conditions that cause the varnish to set up faster.

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