Do-It-Yourself Egress Window

Dig a large hole in front of the wall where you'll install the egress window. Make the hole extend 3 feet from the wall at least 5 feet wide and between 5 and 6 feet deep. Try to keep the hole's bottom and sides as straight as possible.

Spray the foundation wall with water from a pressure washer to remove as much dirt as possible. Mark the egress window's required rough opening dimensions on the wall with a piece of chalk. Use the sill plate (the horizontal board running above the foundation wall) as the rough opening's upper edge.

Cut along the chalk lines with a partner saw and 14-inch diamond blade. Make this initial cut approximately 1/4 inch deep. Follow the chalk lines as closely as possible. Make a second pass over the chalk lines, this time cutting 1 inch deep in cement block walls and 3 inches deep in solid cement walls.

Drill through the opening's two bottom corners with a 1/4-inch masonry bit and a hammer drill. Go inside and mark the rough opening's dimensions with a piece of chalk, using the pilot holes as a guide. Cut along these chalk lines using the 14-inch diamond blade the same way you cut along the exterior chalk lines.

Use a 5-pound sledgehammer to knock the wall out of the rough opening's outline. The wall should break away cleanly along the cut lines. Chisel away any rough spots with a 1/2-inch chisel and a hammer.

Build a square out of pressure-treated 1-by-10-inch boards that will fit tight in the opening. Apply a bead of construction adhesive around the square's outer surfaces and install it in the opening. Push the square into the opening until the outer edge is flush with the wall's outer surface.

Nail the square to the sill plate with 2-inch nails. Hammer 2½-inch masonry nails through the square and into the wall with a power-loaded driving tool.

Return outside. Fold the egress window's nailing fin out so that when you insert the window into the rough opening the fin will press against the square's edges. Apply a bead of construction adhesive around the square's edges where the fin will press.

Insert the window into the opening. Have a friend on the inside hold a level against the window and adjust it so it is centered and plumb in the opening. Have the friend hold the window in place while you hammer galvanized nails through the nailing fin and into the square.

Spray expanding foam into any gaps around the egress window's perimeter from the inside. Install trim on the inside and outside to finish the window.