How to Frame a Curved Window

Order curved window molding from your window's manufacturer. You will need to tell them the window's width from the point where the curve begins. They will also need to know the height from the curve down to where you measured the width.

Position half of the curve above the window. The curve's top end should come up to the window's center and the bottom end should line up with where the window's straight side starts. Drive finishing nails through the molding with a pneumatic nail gun.

Lift the second half of the curve above the window. Press the top end against the first curve's top end. The second curve's bottom end should line up with where the window's straight side starts. Drive finishing nails through the molding.

Measure one of the window's straight sides. Transfer this measurement to a piece of straight molding. Cut the molding to the appropriate length using a miter saw set to a 45-degree cut. Repeat for the window's other straight side.

Hold one piece of molding alongside the window. Press the straight end against the curved molding's bottom end. Drive finishing nails through the molding. Repeat with the second piece of molding on the window's other straight side.

Measure the distance between the two sides' mitered ends. Cut a straight piece of molding to this length, with a 45-degree cut on both ends.

Position the molding beneath the window. The mitered ends should meet the sides' mitered ends to form a 90-degree angle around the window. Secure it in place with finishing nails.