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Install a window

  • Difficulty: hammer hammer
    Close Difficulty
    Beginner Do-It-Yourselfer - Easy
    Intermediate Do-It-Yourselfer - Moderate
    Experienced Do-It-Yourselfer - Difficult
    Professional - Expert
  • Completion Time : 3 Hours

Installing a window is actually a fairly simple project. Although the fit may vary according to the manufacturer, the installation process is basically the same.

There are basically two types of windows: windows with a nailing fin and windows without a nailing fin.

This project outlines the installation of a nail fin window, which means you’ll need to install flashing to ensure the opening is watertight. Installing a nail fin window is more involved than installing a window without a nailing fin.

Finless windows include exterior decorative moulding, which fills the gap between the window and exterior cladding.


Tools and materials required


  • Stapler
  • Mitre Box
  • All-Purpose Knife
  • Caulking Gun
  • Hammer
  • Carpenter’s Level
  • Drill
  • Punch


  • Wood shims
  • Finishing nails
  • Galvanized framing nails
  • Trim and moulding
  • Fibreglass wool
  • Drip cap
  • Self-adhesive waterproofing membrane/Primer aerosol
  • Self-adhesive flashing
  • Silicone-based caulking
  • 2 ½" or 3 ½" No.8 Galvanized screws

Before Assembly


For both renovation projects and new construction, correct measurements are essential.

For new construction:
Measure the window opening at three different places for width, height and depth, and keep the smallest measurement for each; the window will adjust in the opening.

For interior or exterior renovation:
For an interior renovation project, remove mouldings to expose wall studs. Take three measurements of the interior width, and three of the interior height. To measure depth, remove fiberglass insulating wool and measure between the drywall and exterior frame. For exterior renovation projects, measurements are taken from cladding to cladding, either vinyl or brick. You need to take three measurements each for the height and width, and retain the smallest.


The window casing is not always big enough to fill the total thickness of the wall. You must therefore measure for interior and exterior additions, commonly referred to as face flange, to obtain a good finish on both sides of the wall. Once the window is in place, it will be possible to determine what is required.

Face flange on the exterior will be covered with J moulding if the exterior cladding is vinyl, and with brick moulding for brick cladding.

In the interests of insulation, a window should always be installed on the warm side of the wall. There is less risk of condensation on the inside of the wall because the glass is swept dry by the warm air in the room.

This project outlines the installation of a nail fin window, which means you’ll need to install flashing to ensure the opening is watertight.

Finless windows include exterior decorative moulding to fill the gap between the window and exterior cladding. Before installing the window, the existing frame must be watertight with the wall structure. It’s not necessary to remove the exterior cladding. Make sure, however, that the opening is free and clear. Simply add an adhesive flashing on the sill and bottom of the studs and insert the window from the inside of the house. Adjust with shims, then screw securely. Insulate the interior and exterior perimeter and run a bead of caulk.


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climatisation, ossature-du-sous-sol, beton-jointement, beton-escaliers, beton-surface, chauffage, longueur, capacite-liquide, ventilation, volume, poids

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