Window Sash Replacement Is a Cheaper Way to Fix Broken Windows

Double Hung Windows with Sash

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It is that dreaded 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 rain, snow, and insects. But instead of investing in an expensive complete window replacement you can buy a cheaper item called a window sash replacement kit.

This kit allows you to bypass the more labor-intensive job of completely replacing broken or poorly performing windows by switching out only the moving section called the window sash. Key architectural elements such as the trim, casing, and window frame remain in place, with only the top or bottom sashes being replaced.

Total Window Replacement: Necessary or Not?

New replacement windows for your entire house is a stunningly expensive project. Even do-it-yourself window replacement, which is less expensive, can be a daunting prospect for most homeowners. As a result, this is almost always a job that a window company must do for you.

If that isn't bad enough, expensive whole-house window replacement translates to even higher proportional costs for single window replacement. Window companies must raise prices on a single-window basis in order to financially justify such a small job.

Total window replacement is unnecessary in most instances of broken window glass. You might have to take on a full replacement if the overall frame is rotted out, insect-ridden, or is otherwise compromised. By retaining the framing, you also get to keep the exterior window casing, another major job. Unfortunately, compromised window framing often means that the exterior wall itself, along with siding, studs, and insulation, has gone bad. ​

Window Sash Replacement Basics

  • Sash replacement kits are usually tied to your brand of window. Major window companies such as Andersen, Pella, Jeld-Wen, Marvin, and others have window sash replacement programs.
  • Replacement 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 replacements usually are not found in stock at home centers. These are special-order items from the manufacturer.
  • In some cases, purchasing a new-construction window at your local home center, removing the sash, and using it as a replacement may be less expensive than ordering a sash replacement kit. This is possible only when your existing window is an exact, one-for-one match with the new-construction window.

How to Remove the Old Window Sash

There are two chief ways of removing the sash depending on whether you have an older or a newer window. For older wood windows, sash removal can be tricky since you will need to deal with a mechanism called a balancing weight. For newer vinyl or fiberglass windows, sash removal is relatively easy since there is less deconstruction and there will be a spring balance, not a weighted balance.

  • 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. Gently pry off the stop with a flat screwdriver or a small prybar. After 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. Should you try to retrieve this weight or snip the rope and let it fall into the cavity? In most cases, it is easier to cut the rope and sacrifice the sash weight. 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. If you are buying salvaged sashes from an architectural salvage store, the balancing weights are typically not included.
  • Newer vinyl, fiberglass, or metal windows will have a spring-based balance mechanism. With one hand, depress the outermost flexible track. With the other hand, gently pull inward on the top of the sash. With half of the sash out, the other half will pivot out.

Measuring for a New Window Sash

Every window sash replacement kit is brand-specific and contains different parts and accessories. The basic process of measuring for sash replacement on all brands can be summed up as:

  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.