How Do You Install a Gliding Window?

Gliding WindowNot many average people know how to install a gliding window. That does not mean that it is impossible to do. It can be done by following installation instructions carefully and with a little knowledge of a drill, a caulking gun, and a tape measure. Installing a gliding window is easy with the proper tools and by closely following this set of instructions.


Before any removal of old windows or installation of new gliding windows it is important to gather the materials and tools that will be needed to complete the job, according to Pella. Having these items on hand will eliminate the need to interrupt the construction process once it has began. The tools that will be needed are:

  • Tape measure
  • Putty knife
  • Square
  • Phillips and Flat screwdrivers
  • Scissors or utility knife
  • Hammer
  • Drill
  • Drill bits-5/32″ and 1/2″
  • Three inch Phillips screwdriver bit
  • Level
  • Sealant gun


Along with the proper tools it is important to gather the materials that will be needed to complete this gliding window installation. The materials can normally be purchased at local hardware or building supply stores. The materials list includes:

  • Insulating low pressure polyurethane foam sealant
  • Exterior grade polyurethane silicone sealant
  • Foam backer rod or sealant backer
  • 12 to 20 cedar shims
  • Window flashing with foam backing
  • Flashing Tape

Prepare Opening Area

When learning how to infall a gliding window¬†the opening needs to be measured in both width and height with a 1/4″ spacing around the entire window. The opening needs to be checked for plumb and level. If these specifications are not met, it is necessary to add blocking to make the framing the correct size, level, and plumb. This blocking should be installed flush with the exterior of the structure.

Apply Flashing Tape

Measure out the width of the window plus an additional foot of tape. For windows that are flush with the exterior, the flashing can be installed onto the surface with six inches of flashing running up each side of the opening.

An inset installation should have a 3/4″ overlap on the exterior of the opening. Measure 5 1/2″ from one end of the tape and cut a 3/4″ slit. Make another cut one inch away from this cut (6 1/2″ from the end of the tape). Repeat this for the other end of the tape. Install tape along the base of the window opening with the cut pieces being centered on the corners of the opening. Press all flashing tape into place firmly.

Apply a second piece of flashing tape to the interior of the opening with a 1/2″ overlay along the bottom and up the sides. Do not allow this flashing to exceed the opening and intrude on the interior.


Remove the sash from around the window. Drill installation screw holes in the frame and the header of the window opening with the 5/32″ drill bit. Do not drill into the sill portion of the window. These holes should be drilled 7/8″ in from the interior of the window and should be spaced 6″ from each end of the opening. They should not exceed 16″ on center. Counter drill with a guide at 1/4″ from the bit end. Install the attachment clips on the sill not more than 16″ apart. Proper measurement of these locations is essential when learning HOW TO INSTAL A GLIDING WINDOW.

Set in Window

Maneuver the window into the opening by tilting the window so that the bottom portion of the window goes into the frame first. Line the window up with the pencil mark and slide the window down until it sets on the sill. Screw in the top pre-drilled holes to hold the window in place. Insert shims around window at each screw installation site with the exception of the sill area.

Drill pilot holes in the shims and fasten the window into the opening. Fasten the sill by installing the screws into the sill clips. Install the protective plastic screw covers into each hole in the head and the foam covers in the jambs. Replace the sash and check the window for proper function.


Install foam sealant to the interior space of the window opening around the window. Apply the silicone sealant to the seams of the entire window perimeter on the exterior of the window.

Following these simple instructions will ensure that the next new window that is installed is done correctly and easily. Having the correct tools and materials makes the project of how to install a gliding window an attainable goal of any DIY enthusiast.