The do it yourself resource for homeowners from home improvement professionals.

How to Replace Old Windows

If your existing window frame has no rot you should be able to install a replacement window. As long as the frame is square, you can follow these instructions to learn how to replace old windows. Anyone comfortable using a power drill and caulking gun can successfully complete this project. New windows along with a little expanding foam insulation will make your home in the Delaware Valley feel much cozier.

Tools Needed How to Replace Old Windows

Enlist a helper when lifting a window into place. Bigger, heavier windows typically require an extra set of hands.

  • Tape Measure
  • Hammer
  • Flat Pry Bar
  • Paint Scraper
  • Utility Knife
  • Putty Knife
  • Caulk Gun
  • Power Drill
  • Shims

Steps for How to Replace Old Windows

  1. Measure the window’s width from jamb to jamb at the top, middle, and bottom.
    1. Use the shortest measurement.
  2. Measure the height from sill top to the head jamb at the right, middle, and left.
    1. Use the shortest measurement.
  3. Confirm that the window frame is sufficiently square.
    1. Take two diagonal measurements.
    2. If they do not differ by more that 1/4 inch, you can continue.
  4. Buy replacement windows using the shortest width and height dimensions.
  5. Pry off interior window stops.
    1. Take care to preserve them if you want to use them again.
  6. Remove parting beads and take out the upper sash.
  7. If jamb liners are present, take them off with pry bar.
  8. With paint scraper and putty knife, clean off debris.
  9. Fix holes with exterior-grade wood putty.
  10. If old sash weights are present, pull them out.
  11. Dig out any old fiberglass insulation.
  12. Drill 3/8-inch holes into sill and head jamb.
  13. Use holes to insert expanding foam insulation into interior spaces until it comes out of the holes.
  14. Allow foam to harden and scrape off excess.
  15. Run two beads of caulk on the windowsill and up around the edges where the window will sit.
  16. From the interior, set the new window on the sill and tip it into the space.
  17. Make sure that the window is pressed firmly into position.
  18. Secure it with a single screw on the side jamb.
  19. Add shims around the window as you adjust its fit.
  20. Confirm that the window operates smoothly.
  21. Place shims behind predrilled screw holes and install all screws.
  22. Trim off excess shims with utility knife.
  23. Caulk around window edges inside and out.

Energy Efficient Window Replacement

PJ Fitzpatrick can replace framing when do-it-yourselfers encounter rotted window frames. We can fix structural issues before installing modern, energy efficient replacement windows. Contact us about a window replacement estimate today.

Need help with this project?

We have trained professionals that can help.

Contact us today. 1-877-246-4354 Get Estimate

P.J. Fitzpatrick, Inc.

21 Industrial Blvd
New Castle, DE 19720

1-877-246-4354

  • NJ Lic. #13VH10727200
  • DE Lic. #2009603070
  • PA Lic. #PA011323
  • MD Lic. #105494

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