Exterior Window Painting

In order to stand up to the steady abuse from being used and the weather, window painting will require attention to many details and a bit of patience. The details are preparation and repair, choosing a good paint and proper application techniques.

Exterior window painting will be the most time consuming part of any painting project. Easily encompassing up to 50% of the time necessary to paint an entire home, depending on window type or style and condition.

Exterior windows are always exposed to the worst the sun and weather can offer, plus additional wear from opening and closing. An average exterior window will need repainting much sooner than the siding. Giving your windows the best paint job you can will easily pay for itself with easier maintenance and a greater amount of time before the need for a complete repaint.

Exterior Window Types

Windows are manufactured in three basic styles; sash, casement and fixed. There are several variations based on combinations of these three styles. Identify your type before beginning any window painting.

Sash windows open like a guillotine, straight up and down. Also called single and double hung. Single hung has one fixed sash and one that is movable. A variation is sliding windows. These are sashes that move back and forth instead of up and down.

Casement windows open like doors with hinges on the sides. Awning windows are similar with hinges on the top.

Fixed windows do not open and are available in almost any shape and size.

Preparation and Repair

Paying special attention while preparing the surfaces before window painting will provide longer lasting and better-looking results. These basic procedures apply to any style of window.

Clean the Window-The best window painting results start with a clean surface.

Begin with a good washing to remove dirt and dust. Use a scrub brush and mild detergent on persistent deposits. If you use a pressure washer be very careful. The high-pressure water can and will find a way through the window opening. This is the worst way to find out about a leaking window.

Eradicate mold with bleach and water. One part bleach to three parts water should kill any mold. Use a spray bottle for larger areas. The mold will turn white and disappear. Allow the solution to sit on the surface for several minutes before rinsing.

Scrape and Sand the Window and Frame

Scrape away all loose paint and glazing with a sharp stiff putty knife or 5-in-1 multipurpose knife, aka 5-Way. Pay particular attention to the edge next to the glass and the sill. Water has a tendency to enter the glazing and wood at these points. The paint can lose its adhesion and not show signs of peeling or blistering.

Remove all loose glazing with the sharp tip of the 5-Way or use a glazing tool made for this purpose. Be careful while scraping next to the glass. A wrong move can cause a crack in the glass.

All loose or hard caulk needs to be removed as well. The sharp tip of the 5-Way can be used as a digging tool. If the hard caulk is very difficult to remove, dig out a shallow channel for the new caulk. This will increase the thickness of the new caulk and help it adhere.

Sand the entire window frame, sill and window sash after all the loose paint and caulk is removed. Power sanding is the preferred method with hand sanding used in the tight areas and next to the glass. A palm sander works extremely well and is easy to use.

Use 100-grit sand paper or finer for most areas. The idea is to smooth the rough edges and produce a smooth surface. Any roughness on the surface will be highlighted after the window painting.

Common Window Painting Repairs

While scraping you might come across large splits or rotten wood. This is most common on and around the sill. Plus any glazing removed will need to be replaced.

Cracks or splits in good sound wood are a frequent problem needing repair before window painting. Wood windowsills can split in two different ways, many fine cracks or a few large cracks. The repair sequence is similar in both cases.

  • Remove all loose paint with scraping and sanding.
  • Prime the entire area with a quick drying oil base primer.
  • Small multiple cracks can be sealed with a brushable elastomeric sealant. Then finish painted.
  • Large cracks need to be filled with a wood filler, spackling paste or auto body filler. Sand smooth, prime with an oil base primer then finish paint.


Repairing rotten wood is possible if the damage isn’t too extensive. Replacing the wood section is the ideal repair method, but this usually involves a great deal of work and carpentry knowledge. I will explain how to reinforce the area and then patch for painting.

  • Sand or scrape to remove the paint from around the rotting area. Remove enough paint to expose solid wood around the rotted area.
  • Dig out any flaking or crumbling wood.
  • Soak the rotted area with a wood hardener. Hardeners are manufactured in one part or two part epoxy formulations. The epoxy is the best, but more expensive. Allow the area to dry according to the manufactures directions.
  • Fill the area with an auto body filler, Bondo, or a two part epoxy wood filler. The auto body filler works extremely well. Pack the missing wood as tight as possible. Leave the area overfilled. After the filler has dried sand to match the existing profile.


A variation to this method is fixing a broken corner.

  • Lightly sand the broken area and prime with a oil base primer. Allow to dry.
  • Insert flat head nails at several angles. Make sure the nails are under the final surface dimensions. The nails will help hold the auto body filler.
  • Now apply the wood filler. Multiple layers will work better than one thick application. Over fill the area.
  • Sand to match the existing corner profile.


Prime all raw or repaired areas with an oil base primer. If the window was previously painted with an oil base finish and you will be applying a modern acrylic paint, prime the entire window sash and frame.

A quick drying oil base primer is a good choice in most instances. Allow the primer to fully dry before proceeding with applying caulk or glazing putty.

Caulking the Window and Frame

All gaps need to be filled with an elastomeric caulk. These include the trim to the frame, frame to the sill and any other areas where two pieces of wood meet. Do not fill the weep holes or the sash to the frame, unless the window will never be opened.

Reglazing the Window

Replace missing glazing compound after the window has been primed with an oil base primer. The primer will help the glazing putty adhere to the wood.

  • Work the glazing putty in your hands until warm and pliable. The putty will not work if cold. Pre-warm the putty by submerging 1/2 of the can in warm water for several minutes if needed and keep the can in the sun if several windows will be reglazed.
  • Apply more glazing than is needed to the surface with a glazers knife or putty knife.
  • Draw the knife across the glazing with firm pressure. A 45° degree angle is best. Collect the excess putty with your free hand during this process.
  • Smooth any ruff areas with your finger using light pressure.
  • Allow the glazing putty to set-up for 24 hours before painting. Oil base paint can be applied directly to the putty without primer, but it is best to prime before applying water based paints.

Window Painting Techniques and Tips

Use these ideas as a guide and modify or combine according to your own needs and window design. The techniques used for window painting are variations of these two basic designs.

Double Hung Windows

Start with both sashes open and slightly overlapped. Paint the entire outer sash and the exposed areas of the inner sash. Now reverse the positions and paint the remaining areas of the inner sash.

To paint the frame lower both sashes completely and paint the upper portions of the jamb. Allow the paint to dry then raise both sashes and finish the jamb.

Casement Windows

The order for painting casement windows is edges, top and bottom of the sash, sides and then the frame. These windows have edges like a door and these edges show when open. The rule is that the top, bottom and outside edges should be painted with the exterior color.

If possible remove the window sash from the frame and paint on saw horses. This will expose the entire frame and allow a more comfortable window painting experience.

Exterior Window Painting Tips

  • Begin your project as early in the day as possible. Window painting can take several hours depending on the preparation and type of window.
  • If possible remove the sash from the frame. This will make the job of window painting easier.
  • Overlap the primer and paint onto the glass to create a seal. Cut away the excess by carefully running a sharp razor knife close to the wood-glass edge then remove the excess with a single edge razor blade.
  • The best seal is achieved with a small bead of paintable clear caulk after the excess paint is removed.

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