How to Install Vinyl Replacement Windows

• Buy a replacement vinyl window that fits your current window's smallest height and width measurements.
• Carefully save your inside and parting stops as you remove your old window. These can be reused with your new window.
• Install your new window by screwing it into place inside of the window opening. Apply insulation and caulk to ensure your new window is totally secure.

Removing the Old Window

Measure the width and height of the window opening. Measure the top, the middle, and the bottom of the old window for width. Measure the right side, the left side, and the middle of the old window for height. Measure your window from jamb to jamb. Triple check the measurements to ensure that you purchase the correct size window. When purchasing your new vinyl replacement windows, always use the smallest height and width measurements you recorded. Otherwise, your window will be too large.

Purchase a replacement window that fits the hole left by the old window. Replacement vinyl windows will have their dimensions clearly marked on the packaging. Purchase a window at a local home-improvement store, and make sure that it has 2 layers of glass for added insulation. In many cases, your opening will fit a classic replacement window size perfectly, making things simple. For a correct fit, the replacement window should be approximately ⁄4 inch (0.64 cm) narrower than the opening width and height. If your window measurements are in between sizes, round the measurement down. If your windows are an unusual size and a corresponding size of replacement window is not in stock at the home-improvement store, ask about custom ordering the vinyl windows.

Remove the inside trim, moldings, and stops with a broad chisel. Slip the broad chisel just outside the edge of the currently installed window. Wiggle the chisel back and forth to loosen the paint and caulking between the window frame and the sashing. When one panel loosens up, gently pull it away from the frame. Once you’ve removed the trim and molding, don’t throw it away. Save these items for later use. In all likelihood, your window will have 3 stops: one at the top, one on the left, and one on the right side of your frame. Not all windows have stops. If yours do not, don’t worry. In this case, you only need to remove the trim and moldings.

Remove old cords and weights from the bottom sash if necessary. Weights and balances are used on some older models of aluminum or vinyl windows, but not on most modern windows (quickly scan your window frame, as they'll be noticeable and dangling on the left and right sides). Carefully remove these items from the frame, using a pair of scissors to cut the cords if needed. You can throw old weights and cords away, since your new window will come equipped with these items.

Pry out the parting stops at the top and sides of a double sash window. Parting stops keep the sashes separate, but they're only relevant for double sash windows. Using your broad chisel again, pry the parting stops away just like you removed the first set of stops. Once you've pulled the stops out, set them aside. You'll reinstall them once the replacement window is in place. Be careful not to jam your chisel into the window frame, since you’ll install the replacement window in the same location.

Remove the top and bottom sashes once the stops are out. The sashes should no longer be held in place against the window frame. Lift out the top sash first by pulling the bottom lip forward and out, away from the lower sash. Remove the bottom sash by pulling its upper lip upwards and outwards, straight towards your body. Set both sashes aside. Dispose of the old sashes once you’ve removed them from the wall.

Remove the securing staples that hold the aluminum tracks in place. If the existing window is fitted with aluminum tracks, use a pair of pliers to pull out the staples holding the tracks in place. Once the staples are out, lift out both the window sashes and the aluminum track. If the tracks are held in place with screws, remove the screws using a Philips-head screwdriver, then pull out the tracks.

Preparing the Window Opening

Scrape any loose paint or stain off of the window jambs. There may be paint remnants and loose caulk or expanding foam stuck to the window jambs. Run a paint scraper along the interior and exterior surfaces of the window jamb. Keep the scraper at a 30° angle and apply firm pressure to scrape the jambs clean.

Make sure that your replacement window fits in the frame. Close and lock the window sashes on the replacement window. Set the new window in the opening to verify that your earlier measurements were correct and the window fits snugly in the opening. Then, remove the new window from the opening in your wall.

Apply caulk to the inside and outside edges of the stool. The stool is a flat board jutting out from the wall at the bottom of your window. Visit your local hardware store and purchase 1 tube of professional-grade exterior paintable caulk. Run a thin, even bead of caulk along the edges of the stool where it meets the window apron (the vertical board located just below the stool) and the window sill. Also apply caulk to the outside blind-stops and along the top of the opening's header. Caulk will keep the stool of the window from being damaged by water drops. It will also prevent drafts from entering your home.

Positioning the New Window

Set the replacement window into the frame opening. Set the bottom of the window in first and lift the rest of the window up into place. To secure the window, butt the exterior window frame up against the opening blind stops. Do this from the interior wall side, and take care not to push the window clear out the other side of the wall. Make sure that the sashes are still locked when you set the window in place.

Use a level tool to ensure that the window is level. The replacement window may not sit flat in the window hole once you’ve set it in place. To determine if it’s level, set a level on the top of the lower sash and look to see if the indicator bubble floats to the center of the tube. Even if the window looks level, it may be off-kilter to a very slight degree. If you don’t have a level, purchase one at a local hardware store. The tool resembles a metal bar that’s roughly 18 inches (46 cm) long.

Insert shims beneath the window until it sits flat and opens smoothly. Shims are nearly flat pieces of wood that slightly raise the level of one side of the window. If the installed window doesn’t cleanly open and close or if it’s not level, place 1 shim at a time beneath the low side to raise it up. To secure the frame, place shims at the middle of the frame and at the middle of the top and bottom sashes as well (until you get a level read). Once the shims are in place and the window is square and opens and closes smoothly, snap off the shim stems.

Install shims behind screw holes. This will prevent the frame from becoming warped when you tighten the screws through the window and into the frame. Place shims directly behind the jamb where each screw will be inserted. When you insert the screws, they’ll pass directly through the shims. If the ends of the shims stick out once you’ve screwed the window into place, snap them off.

Securing the Window in Place

Use screws to secure the window to the opening in your wall. Most replacement vinyl windows are screwed in place. Take your replacement screws and install them through the screw holes in the window sashing. Align the screws with the pre-existing holes in the wooden window frame. Tighten the screws with a screwdriver until they’re firmly in place. The replacement window should have come with screws for installation when you purchased it. So, you won’t need to purchase these screws separately.

Install insulation around the window between the frame and opening. Use low-pressure expanding foam made from polyurethane. Shake the can and attach the narrow tube as directed. Stick the point of the tube in the gaps around your installed window, and squeeze the trigger until the gap is filled with foam. Be careful if you’re using traditional expanding foam for the insulation, as installing too much insulation on top and bottom may cause window to bow. Insulation will block drafts and keep the window from letting hot or cold air you’re your home.

Reinstall the stops, trim, and molding that you removed earlier. Depending on the style of replacement vinyl windows that you purchased, these items may need to be screwed into place, or they may be held in place by pressure. If they need to be screwed in place, the screws will be included in the replacement window packaging. Work gently with the stops, since they’re relatively delicate and can break easily. If you do accidentally snap a stop, don't stress. Find the right stop by bringing your window's measurements to a home improvement store.