How to Install Basement Windows

Installing basement windows yourself will save you hundreds of dollars and add light and warmth to your basement and help to keep it dry. Although it is not a complicated process, to install basement windows, you will need some knowledge of masonry tools and power equipment. Consider the following steps when installing basement windows.


  1. 1
    Decide where the window will be and mark out the outline of the window with masking tape
  2. 2
    Build a temporary wall 3 inches (7.62 cm) back from where the window will be to support the ceiling as you cut out the window opening.
  3. 3
    Staple plastic sheeting so that it hangs from the support wall to contain the dust, sealing off the area between the ceiling joists.
  4. 4
    Drill pilot holes all the way through the basement wall at each corner of the window outline and at the center point of the top and bottom lines.
  5. 5
    Measure the dimensions of your proposed window opening and go outside to the exterior wall of the basement.
  6. 6
    Level the bottom of the window opening from the center pilot hole on both sides, measure out the dimensions of the window outline, and mark it with masking tape.
  7. 7
    Drill level holes through the wall at the corners using the pilot holes as a guide.
  8. 8
    Using a 14 inch (35.5cm) concrete saw with a diamond blade, cut a 1/2 inch (1.27 cm) groove into the inside basement wall at the center bottom mark and continue around the outline ending where you began.
  9. 9
    Finish cutting the window from the outside basement wall by following the marked, leveled outline and making the same cuts as you did on the inside basement wall.
  10. 10
    Use a small sledgehammer to break the wall blocks out of the outline so that an opening is created.
  11. 11
    Smooth the sides of the opening by chipping away any rough spots with a brick chisel.
  12. 12
    Fill the exposed wall blocks with concrete, stuffing newspapers into them to keep the concrete from falling down through them, and cover it with plastic sheeting.
  13. 13
    Screw 3 inch (7.62 cm) deck screws partially through the bottom wooden sill of your window and push them down into the concrete.
  14. 14
    Hoist the header frame into place and screw it to the ceiling joists.
  15. 15
    Cut the sides to fit the opening between the bottom sill and the header, bang them into place, plumb the sides with your level and screw them at an angle to the sill and the header.
  16. 16
    Anchor the sides of the frame to the basement wall with concrete screws.
  17. 17
    Seal any gaps between the window frame and the basement wall with exterior caulk.
  18. 18
    Remove the temporary wall with its hung plastic sheeting.
  19. 19
    Center the window in the opening and temporarily tack shims into place to steady it.
  20. 20
    Check the window to be sure it is level and screw it through the nailing fin to the frame.
  21. 21
    Apply exterior caulk generously around the window edges between the window and the frame.
  22. 22
    Create a bevel under the window by wetting the ledge, adding mortar and forming the bevel with a small trowel.
  23. 23
    Allow the new window to set and dry thoroughly, a process that can take two or three days depending on the dampness of your basement.


  • If you are installing a replacement window in an existing window frame, consider a replacement window kit.
  • Tack the window pieces in place before screwing them in all the way. This will make any adjusting you might need to do easier.


  • Always be sure that your body is stable and balanced when sawing to avoid serious injury.
  • Always wear safety equipment such as a respirator and safety goggles.

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Categories: Doors and Windows