DIY Wooden Window Frames

Written by kevin mcdermott
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DIY Wooden Window Frames
A wooden frame will give your windows a finished look. (A shadow of a window cast on a wall in black and white image by David Smith from

Trimming out a window with an interior frame gives it a finished look and also seals off the spaces between the window casing and the wall, helping the insulation work better. There are numerous ways to frame a window, depending on how elaborate you want the design to be and how comfortable you are with more complex woodworking tasks. For beginners, a basic four-corner mitre is usually the best choice.

Skill level:

Things you need

  • Tape measure
  • Level
  • Pencil
  • Wood trim
  • Mitre saw
  • Trim nails
  • Hammer

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  1. 1

    Set a level along the top of the window opening, 1/4 inch up from the edge. Run your pencil along the level to mark a line there. Extend the line 1/4 inch beyond both ends of the opening.

  2. 2

    Measure the line and mark it out on a piece of trim. Lay the trim on a mitre saw with the bottom edge of the trim facing the blade and one of the two marks directly under the blade.

  3. 3

    Swivel the blade so that it points away from the main portion of the trim at an angle of 45 degrees. Cut the trim. Position the other mark under the blade, swivel the blade to 45 degrees in the opposite direction, and cut it again. The resulting piece should be longer across the top edge than the bottom, with angled mitre cuts at both ends.

  4. 4

    Install the board along the top of the window, on your line, with your trim nailer, putting pairs of nails every foot or so. The two ends of the trim should come out over the edges of the window by 1/4 inch at the bottom side of the trim, with the mitre cuts angling out further.

  5. 5

    Measure and cut trim for the other three sides of the window in the same fashion. Nail them all in with your trim nailer. The 45-degree angles of the mitres will form the 90-degree corners of your window frame.

Tips and warnings

  • Wear eye protection when cutting the trim.

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