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How To Install a Window Sash Replacement Kit

Tom Silva teaches three apprentices from our Generation NEXT program how to install a window sash replacement kit.

If your house has double-hung windows equipped with sashes that are in desperate need of replacing, you have three options: install a window sash replacement kit, install a frame and sash unit (also called a “boxed” unit), or replace the entire window with a new one (this is the most costly and invasive).

In this video, Tom Silva teaches three apprentices from our Generation NEXT program how to install a window sash replacement kit. Of the three options, it is the simplest and least expensive. The kit consists of two jamb liners as well as a top and bottom sash.

Steps for Installing a Window Sash Replacement Kit

This approach requires that the existing window frame (jambs and sill) be in good condition.

1. Measure the existing frame

  • Starting at the inside edge of the window side jamb, measure straight across to the opposite jamb. This number is your width.
  • Next, measure from the sill (where the exterior of bottom sash contacts the sill) up to the head jamb. This number is your height.
  • To ensure that you order the correct window sash replacement kit, refer to the manufacturer’s instructions on how to order based on these measurements.

2. Remove the old sashes

  • Start by prying off (or unscrewing) the window stops on the left and right side of the window sash. The window stops may be caulked to the trim, so it is best to score the joint first with a utility knife or putty knife. When prying the stops off, use care not to break them so that they can be reused.
  • Next, pull out the lower sash and disconnect the cord or chain. Cut the cord or chain and let the weight fall into the pocket behind the trim.
  • Now remove the parting bead, which is the small piece of trim that sits in a recessed groove (called a dado) in the sides and head jambs. The parting bead will likely need to be removed in pieces; that’s okay as they can be discarded.
  • Remove the upper sash and disconnect the cord or chain. Cut the cord or chain and let the weight fall into the pocket behind the trim.
  • Remove the pulleys, which are typically screwed into the side jambs with slotted screws. If the screws are heavily painted over, align the slotted screwdriver over the screw and tap lightly to chip away the paint. Discard the pulleys.

Note: it’s ideal to remove the weights and fill the weight cavity with insulation such as low-expanding spray foam. Depending upon the age and condition of your windows, this may be easier to do by removing the window trim which sits directly over this cavity.

3. Inspect the existing frame

  • Ensure that the existing frame is in good condition. Repair or replace any rotted sections.
  • Then check the frame to ensure that the sill and head jambs are level, and that the side jambs are plumb.

4. Install the jamb liners

  • Following the manufacturer’s placement recommendations, install the liner clips. One is typically required about 4-inch down from the head jamb and 4-inch up from the sill, then a number of them in between depending upon the height of your window jamb. In this video, Tom Silva installs five clips on each side.
  • Install the clips by registering them against the exterior window trim, then pulling them back about an 1/8-inch.
  • Drill a starter hole, then nail in place using 1 to 1-1/4-inch galvanized roofing nails. Don’t drive the nails in very tight; just bottom them out so that the brackets can be tapped forward or backward if necessary. Ensure that the brackets are installed level so that the tabs register in the jamb liners properly.
  • Snap the jamb liner in place on each side, ensuring that the weather stripping sits over the exterior trim. Make sure that the jamb liner fully engages with each tab of each bracket.

5. Install the sashes

  • Starting with the top sash, tilt it into the opening engaging the lower pin into the metal cam in the liner.
  • Then slowly lower the other side until its pin meets the metal cam on the other side.
  • Now, slowly lift the sash and depress the jamb liner on both sides as you go to ease the sash into position.
  • Once it snaps into place, push the window up. Repeat the process for the lower sash.
  • Lock the window.

6. Replace the window stop

  • Nail the side and head stops, registering them against the jamb liners. If necessary, rip them to fit on a table saw.