How to Frame a Custom Window

Sizing a Rough Opening for a Window

• 1

  Measure the rough opening size for your window, using a tape measure. Precise measurement is a must to fit the window securely. Oversizing the opening is better than undersizing it. You can always fill the gaps with shims around the window frame.

• 2

  Size the frame opening 2 inches higher and 2 inches wider than the window itself. This extra space will also allow for the window frame to be plumbed and leveled so that it opens and closes correctly.

• 3

  Measure the rough opening for aluminum and vinyl windows with a tape measure. Manufacturers usually undersize these windows. Your measurement for the rough opening must be the identical width and height as the new window.

Framing for the Window Rough Opening

• 4

  Remove the drywall to expose the studs, using a drill and regular saw. Determine the location of the window rough opening and install king studs. A king stud is the additional vertical stud that supports the studs in the original wall, of which that your window will be placed between. Measure and cut two 2-by-4 king studs to size, using a saw. Fit the king studs between the top wall plate and the bottom wall plate, one per side at the exterior edge of the rough opening.

• 5

  Measure the space between your king stud and the original wall studs to install "blocking". The "blocking" adds additional support to the wall. Cut two small two-by-fours, nail horizontally, one on each side, between the two kings studs and the original wall studs.

• 6

  Measure the distance between the bottom window's opening and bottom wall plate. Make the cripple studs by cutting three 2-by-4s. Nail two of the cripple studs to the insides, one per side, parallel to the king studs. Nail the remaining cripple stud into the center of the rough opening to the bottom plate.

• 7

  Create a window sill by cutting a two-by-four to nail on top of the cripple studs. Use a carpenter's level to level the sill. Measure and cut two additional two-by-four pieces to sit next to the king studs, one on each side, on top of the window sill, and below where the header will sit. These are called trimmer studs, and they should be nailed at an angle through the sill.

• 8

  Construct a header by measuring and cutting 2-by-8 lumber to the width of the space between your two king studs. Place this header on top of the trimmer studs and nail through both the king studs.

• 9

  Nail three small wood blocks to sit between the top wall plate and the header. Position one in the center of the header and one on each side of the king studs. Nail them through the wall plate and the studs.

Installing the Window

• 10

  Lift the window into the rough opening from the outside. Hold it there firmly while your assistant helps from the inside. If there are any reinforcing blocks or braces on the window, do not remove them until the window has been nailed securely to the house.

• 11

  Run a 4-foot spirit level across the sill to check for level. Tilt the window away from the opening just enough for the helper inside to apply a bead of waterproof sealant around the rough opening. Press the window into place.

• 12

  Hammer 10d galvanized casing nail through the studs, securing one lower corner of the window to the lower wall plate. Insert flashing over the head casing and slip it under the siding.

• 13

  Level the window with a 4-foot spirit level. Use another nail to secure it in place when the window is even. Apply caulk under the sill.

• 14

  Cut a new piece of drywall to fit inside the space you removed, using a drywall saw. Attach the drywall to the studs by placing nails along every 8 inches on the studs. Apply the mud along the seams of the drywall, using a flat-edged mud trowel. Let the mud dry for 24 hours and then sand it for smoothness. Add a wall primer to this new drywall with a paintbrush; let the primer dry before you paint over this area.

• 15

  Add insulating foam in the gaps between the window frame and the wall. Install moistureproof membrane around the window. Seal with caulk both on the inside and outside around the window frame.