How to Install an Egress Window

When renovating your basement to use as an office, bedroom or other living space, you are required by law to install an egress window to act as an escape route in case of an emergency. Here are the steps you can take to install an egress window yourself.


  1. 1
    Find out how large your egress window needs to be. Requirements vary based on where you live, so look up local codes on the subject. It will likely need to be about 6 square feet (1.8 meters), and the bottom of the window opening will need to be no more than 44 inches (1.1 meters) off the floor.
  2. 2
    Measure and mark your cut on the inside wall of your basement with a grease pencil.
  3. 3
    Build a temporary support frame inside the basement. You need to do this if you are cutting into a wall that is perpendicular to the floor joists above.
    • Make a 9-foot-wide (2.7 m) frame out of 2-by-4's, erected about 3 feet (0.9 m) from the where the window will be installed. Erect and secure vertical 2-by-4s inside the frame directly underneath the joists.
  4. 4
    Hang plastic sheeting along the frame to contain dust.
  5. 5
    Drill a pilot hole in the center of the bottom cutting line. Use a drill bit that is long enough to go through the wall. Make sure the drill is perfectly level when it penetrates the wall.
  6. 6
    Dig a hole under the area where you are adding the window. It needs to be at least 6 inches (15 cm) deeper than the bottom of where the window will be. The hole should be about 4 sq feet (1.2 sq m).
  7. 7
    Measure and mark the cut on the outside. Use the pilot hole as a reference point.
  8. 8
    Cut the hole for the window with an electric 14-inch (35.5 cm) concrete saw. Cut only about 1/4 inch (cm) your first time around the lines. Then, after you have established a straight groove for the blade to cut through, make deeper cuts, until you have cut halfway through the wall.
    • You can rent a concrete saw. Renting a diamond blade is also recommended.
    • You can use a 12-inch (30 cm) blade if your wall is only 8 inches (20 cm) thick.
    • Wear hearing and eye protection, a dust mask, and gloves when operating the saw.
    • Plug the saw into a GFCI outlet.
  9. 9
    Repeat the sawing process on the outside wall.
  10. 10
    Tap the blocks where the hole will be with a large hammer to remove them. Start at the top-center.
  11. 11
    Chisel the sides of the hole to smooth them enough to fit the rough window frame.
  12. 12
    Fill the bottom block cores with concrete.
    • Avoid using too much concrete by stuffing newspaper into the cores beforehand.
    • Cover the wet concrete with plastic sheeting.
  13. 13
    Install the rough frame. Saw pressure-treated 2-by-10s to fit the perimeter of your hole.
    • Partially drive 3-inch (7.6 cm) deck screws into the bottom 2-by-10, which will be stuck into the wet cement to hold the sill in place.
    • Screw the top of the rough frame into the floor joists.
    • Use concrete screws to secure the sides of the rough frame to the block wall.
  14. 14
    Apply an exterior caulk around the rough frame and concrete walls.
  15. 15
    Remove the temporary support frame.
  16. 16
    Install window and box. Most windows will come with installation instructions, but it is likely that you will need to:
    • Caulk around the edges of the box.
    • Unfold the metal fins of your untrimmed window and nail them into the box.
    • Apply mortar to the area between the box and the wall.


  • Before beginning the project, inspect for ductwork, wiring and buried utilities that might be in the area where you're working.
  • If your basement wall is solid concrete, as opposed to concrete block, it is recommended that you hire a professional to cut the hole.

Things You'll Need

  • Tape measure
  • Grease pencil
  • 2-by-4s
  • Plastic sheeting
  • Concrete demolition saw
  • Hammer
  • Caulk gun
  • Chisel
  • Extension cord
  • Safety goggles
  • Dust mask
  • Hearing protection
  • Spade
  • Concrete
  • Pressure-treated 2-by-10s

Article Info

Categories: Doors and Windows