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

How to Replace a Window

At P.J. Fitzpatrick, replacing windows is just one of our many specialties, but sometimes homeowners want to do it themselves. learning how to replace a window takes time, patience, and some builder’s knowledge. If you think you have all three, our step-by-stop guide can help you remove your old single-hung window and install your new one. Here’s how to replace a window:


The first thing you’ll need to do before you even buy your replacement window is take a thorough measurement of your current window.

  1. With your measuring tape, measure the width of your window (from jamb to jamb) in three areas: across the top, across the middle, and across the bottom.
  2. Then, measure the height (from the top of the sill to the bottom of the head jamb) in three places: on the left, in the middle, and on the right.
  3. Take the smallest width measurement and smallest height measurement and use these as your references.

Removing the Window Trim

Use your pry bar (and hammer, if you need it) to gently remove the window trim and jamb extension (the piece of wood that’s been attached to the jamb to make the window fit evenly with the wall).

Removing the Window Sash

Since your new window will sit inside the old frame, the next step is to remove the sash.

  1. Carefully pry off or unscrew the interior wooden stop pieces (you’ll use these later) to remove the lower sash.
  2. Then, take out the parting beads (if they’re there) to remove the upper sash. If the window uses weights (many old homes do), cut the sash cords or chains.
  3. After you remove the inner sash, remove the outer sash the same way, however, don’t remove the parting beads, as you’ll use these later.
  4. Clean the jambs and window sill thoroughly. Scrape off any loose/blistered paint, then fill any holes you see with caulk.

Installing the New Window

Drafty and inefficient windows are often the result of an improper or a rushed installation, so take your time installing your new window.

  1. Start by “dry fitting” the window: before you use any caulk, place the window in the opening to make sure that it will fit. If it does, continue by applying a continuous bead of caulk along the windowsill.
  2. Then, slide your new window into place and use your level to make sure it sits evenly both vertically and horizontally. If it doesn’t, you can use your shim to adjust it.
  3. The window should come with its own screws that you can screw into the pre-drilled holes in the frame to secure the window.
  4. Once your screws are secure, slide the top and bottom sashes up and down to make sure they move smoothly. If they don’t, use the adjustment screws in the side jambs to adjust the window frame.
  5. Then, caulk the inside of your window and reinstall the inside stops.
  6. After that, you can add any insulation, trim molding, jamb extensions, or paint/stain that may be needed.

Tools & Materials

  • Hammer
  • Drill
  • Caulk, Caulk Gun
  • Replacement Window
  • Shims
  • Chisel
  • Screwdriver
  • Pry Bar
  • Measuring Tape

Need help with this project?

We have trained professionals that can help. Contact us today. 1-877-246-4354

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