How to Take Out Your Old Windows and Install New Ones

Stephen Doudna II, the DYI Guy shows how to remove the old windows from a really old house, measure for new replacement windows and install them, step-by-step. He makes this DIY project easier than you think!

How to Remove and Install Replacement Windows (DIY Guide)

Hey guys, in today’s video I’m going to show you how to take out your old windows and replace them with new energy-efficient windows.

Window Terminology Basics

Before getting started, it’s important to understand a few key parts of a window:

Window trim – Holds the sash in place

Lower sash / upper sash – The moving parts of the window

Window stool – The flat interior ledge

Window sill – Slopes outward to shed water

To measure your window, measure from the sill to the top jamb. Check both sides to account for any unevenness.

Checking If the Window Is Square

Use a speed square at the corners to check alignment. Even older homes can be surprisingly close to square.

Removing the Old Window

To remove the old window, you’ll need to cut through years of paint and caulk using a multi-tool or utility knife.

Carefully work along the trim and edges until you can pry the stops loose.

Remove the sash and any internal components, taking your time to avoid damaging the frame.

Measuring for the New Window

Your replacement window will slide in from the inside and rest against the exterior stops.

Measure width and height carefully. Manufacturers will typically deduct about 1/4 inch total to allow proper fit.

Installing the New Window

Before installation, dry fit the window to confirm sizing.

Apply a bead of silicone caulk around the frame and corners.

Add flashing tape along the bottom to prevent moisture intrusion.

Insert the window bottom-first, then tilt it into place against the stops.

Secure the window with screws through the pre-drilled holes, using shims where needed to ensure level and square placement.

Sealing and Insulating

Fill any gaps with low-expansion window and door foam to avoid warping the frame.

Once dry, trim excess foam and reinstall interior trim pieces.

Final Steps

Caulk the exterior edges of the window to seal against weather.

Fill nail holes, touch up paint, and your installation is complete.

FAQ: Window Replacement Basics

How long does it take to replace a window?

Most standard windows take 30 minutes to 1 hour to replace once prepped.

Do I need to remove the entire frame?

Not always. Many replacements fit inside the existing frame if it’s still in good condition.

How tight should the new window fit?

You should have about 1/8 inch of space around the frame for proper adjustment and insulation.

What type of foam should I use?

Use low-expansion window and door foam to prevent bowing or binding the frame.

What is the most important part of installation?

Proper sealing and flashing are critical to prevent water damage and air leaks.

If you are researching the installation process, pair this page with a quick DIY window installation guide and what affects replacement window timing. It also helps to review different window types before choosing a product.