How to Add a Bay Window

If you need more light in your living room, consider adding a bay window. Bay windows can also make a small room appear larger. Most homeowners can handle adding a small bay window on their own. Because the window protrudes from the home's exterior, it must be adequately supported and sealed off to prevent leaks.

Things You'll Need

• Pry bar
• Hammer
• Tape measure
• Pencil
• Bay window and frame
• Support braces
• Cripple studs
• Level
• Cable clamp
• Wood screws
• Screwdriver
• 2x4 boards
• Plywood
• Fiberglass insulation
• Saw
• Roofing paper
• Staple gun
• Roof shingles
• Roofer's nails

Instructions

1. Remove the existing window and frame from the wall. Take out the sash stops on the sides and top of the window. You may have to use a pry bar and hammer to pry off the sash tracks.

2. Measure your new bay window. Mark these dimensions on the home's exterior. If you need to expand the window opening, cut through the old wall studs. Use lengths of 2x4 to frame the new opening.

3. Nail the windowsill plate in place. Cut several pieces of 2x4 to use as cripple studs to support the windowsill. The studs should be long enough to run from the windowsill down to the floor. Attach one cripple stud on each edge of the windowsill. The number of cripple studs required for the middle supports depends on how wide the bay window is. A small window may be fine with only one cripple stud in the middle, but a larger window may need several.

4. Install the bay window's support brackets onto the windowsill, over the cripple studs. Windows up to five feet wide can be supported by only two brackets. Larger windows may need three or four to support the entire weight. Slide the bay window onto the support brackets and push it into the house through the window opening.

5. Check the window frame to see if it is level. If it is uneven, use shims to raise up the lower side until it matches the high side. Secure the bay window frame temporarily by using a cable clamp on the outside and screws on the inside. Snap the window panes into the frame and re-check to make sure it is still level. Permanently attach the window frame to the home with wood screws once you are satisfied that it is in the right position.

6. Use sections of 2x4 to frame the roof cap. Attach it to the home above the bay window. You can fill the interior of the roof cap with fiberglass insulation to keep heat from leaking out of the home. Attach plywood panels to the rafters to conceal the interior.

7. Attach wood trim and a metal drip cap to the outer roof edge. Staple roofing paper on top of the plywood panels. Use roofer's nails to attach shingles to the roof cap. Lay the shingles in rows, with each row overlapping the previous row to keep water from seeping in. Use step flashing at the connection point between the roof cap and the house.

Tips & Warnings

• Consider the direction of the sun when deciding where to add a bay window to your room. Windows facing south will get the most sunlight.