The do it yourself resource for homeowners from home improvement professionals.

How to Build a Window Frame

Whether you’re in need of a new window frame for your home, shed, playhouse, or another structure, building your own window frame is relatively easy and only requires a few materials. Here, our window installation experts explain the steps for how to build a window frame:

  1. First, use your measuring tape to measure the rough opening of the window.
  2. For the width, start at the inside of the drywall and measure across to the exterior side of the stud.
  3. Then for the length, measure from the bottom cripple stud to the top cripple stud.
  4. Next, use your table saw to cut two pieces of lumber to your width measurement minus 3/8″ and two pieces of lumber to your length measurement minus 3/8″. (For example: if your width measurement is 20″ and your length measurement is 30″, you’ll want to cut your pieces to 19 5/8″ and 29 5/8″.)
  5. After that, tilt your saw blade to a 45-degree angle and cut each of the corners of your four pieces of wood. (Make sure you cut all of the pieces at an outward angle.)
  6. Dry-fit the pieces of wood together to make your window frame.
  7. If the pieces fit well, you can use wood glue to glue them in place.
  8. To make sure they stay in place as they dry, use clamps to clamp them together.
  9. After the glue dries, remove the clamps.
  10. To make the frame even more sturdy, use your hammer and nails and nail the pieces together at the corners.
  11.  If you want to add a decorative cross of wood molding in the middle of the frame, measure the inside width and length of your window frame.
  12. Then, cut your pieces of molding to fit inside the window.
  13. Next, overlap one over the other and glue into place. You can also cut a piece the width of the molding out of the middle of one piece to make the two pieces sit flush together.
  14. Once the pieces are glued, you can use your hammer and nails to secure them to the window frame.

Tools & Materials

  • Measuring tape
  • Table saw
  • Wood glue
  • Clamps
  • Hammer, nails
  • Molding (optional)

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