Window Sash Replacement Basics

Double Hung Windows with Sash

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It is that moment when a rake is swung or a ball is thrown in the wrong direction. Glass shatters and now you have a broken window that lets in the rain, snow, or insects. Does a broken window mean entirely installing a new window—including the high price?

Fixing the Window Sash

Not necessarily. Instead of investing in a complete window replacement, you can buy and install a far less expensive window sash replacement kit.

Key architectural elements such as the trim, casing, and window frame remain in place, with only the top or bottom sashes being replaced. With this kit, you'll bypass the labor-intensive job of completely replacing the broken or poorly performing window by fixing only the part that needs fixing: the window sash.

Window Sash Replacement Basics

Replacement window sashes usually come as part of a multi-part kit. Kits usually comprise a top or bottom sash (or both), compression jamb liners for both sides of the window, a sill dam, and a head parting stop.

Window sash replacement kits are usually tied to a specific window brand. Major window companies such as Andersen, Pella, Jeld-Wen, Marvin, and others have window sash replacement programs.

Individual sash replacements are not found in-stock at home centers, though you may be able to special-order them through the home center.

When Total Window Replacement Is Needed

Installing new replacement windows for your entire house is a stunningly expensive project. Even do-it-yourself window replacement—which trades much of the expense for homeowner labor—can be a daunting prospect. As a result, window replacement is usually a job best left in the hands of a window company.

Total window replacement is unnecessary in most instances of broken window glass. If the problem is only that of broken glass—and the damage is localized—you can replace the window sash only.

In some cases, you'll need to replace the whole window or have a window company or contractor to come in to make extensive repairs. This is usually when the damage extends beyond the window or when the sash is a type that is meant to be fixed in place (not merely a window sash that is stuck in place due to paint or expansion). If you're doing any type of major construction around or including the window, it makes more sense to buy a new window.

When to Replace the Whole Window

Overall frame is rotted out

Insects have damaged the window

Studs, wallboard, or siding that connect to the window area are damaged

Insulation that surrounds the window is gone or compromised

Window sash is fixed in place, not removable

During major remodeling

Where to Find Window Sash Replacements

  • Marvin: Marvin's Ultimate Tilt Pac Double Hung Sash Replacement System Window is available in sizes up to 10 feet high and 5 feet wide.
  • Jeld-Wen: Jeld-Wen has a sash replacement kit for its wood-clad Siteline windows.
  • Andersen: Though not affiliated with Andersen, WindowParts.com is a large supplier of individual Andersen window parts, including sashes.
  • All Brands: In some cases, purchasing an in-stock new-construction window at your local home center is your best source of a replacement sash. The new window becomes a parts window. You can do this only when your existing window is a perfect, one-for-one match with the new-construction window.

How to Measure For a New Window Sash

  1. Remove extraneous items such as screens, storm windows, and shutters.
  2. Remove the old sash and weights.
  3. Measure the height and width of the window opening with a tape measure. Measure at three places on both the side and top, choosing the smallest of the three measurements for the side and the top. Do not choose any of the larger figures because the new sash will not fit the opening.
  4. Order your new sash accordingly. 

How to Remove the Old Window Sash

For older wood windows, sash removal can be tricky since you will need to deal with the balancing weight mechanism. For newer vinyl or fiberglass windows, sash removal is easier since they will have a spring balance, not a weighted balance.

Windows With a Balancing Weight

  1. Older wood windows will usually have a stop, a thin vertical strip of wood that prevents the window sash from coming out. Score the edges of the stop with a utility knife to cut any paint that connects the stop to the wall.
  2. Gently pry off the stop with a flat screwdriver or a small prybar.
  3. After the sash removal, you are left with the balancing weight: a heavy lead or iron cylinder enclosed in a hidden cavity and attached to the movable sash with a rope. In most cases, it is easiest to cut the rope and sacrifice the sash weight, letting it fall into the cavity.
  4. Lift the sash out and place it away from the work area.

The sash replacement kit will have a balancing mechanism with a coil spring block and tackle that replaces the weighted system. This new mechanism will keep your replacement sash in place and properly moving up and down.

Warning

If you are buying salvaged sashes from an architectural salvage store, the balancing weights are typically not included. In this case, be sure to preserve your window's balancing weight.

Windows With a Spring Balance

Newer vinyl, fiberglass, or aluminum windows will have a spring-based balance mechanism.

  1. With one hand, depress the outermost flexible track.
  2. With the other hand, gently pull inward on the top of the sash.
  3. With half of the sash out, the other half will pivot out.
  4. Lift the window sash out and place it safely away from the work area.