Installing a window

Windows are normally delivered with precise installation instructions from the manufacturer. It's important to remember that, no matter how much you pay for windows, installation is crucial. Poor installation will reduce energy efficiency, air and water tightness, resistance to weather and will likely interfere with the operation of opening and closing mechanisms.

The frame of the house is typically made of 2 in. × 6 in. studs, covered on the outside with sheathing that provide stiffening for the frame. In turn, the panels are covered with an air barrier that is cut around door and window openings.
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1. Protection against air infiltration
2. Place and secure the window
3. Fasten the window
4. Install the dripcap
5. Insulate the window
6. Cut the shims
7. Nail the brick mould
8. Install the interior mouldings
To install a replacement window, you simply take out the old sashes, keep the existing frame and molding and put in the new window.

Safety precautions
Glass breakage may occur; always wear safety glasses and gloves. Dispose of waste in a safe place. A clean working area may prevent serious damage or injury.

Take out the old window
  • If your window is fitted with a storm window, remove it first.
  • Using a 1” wood chisel and hammer, carefully remove interior mouldings, starting with the longer ones. Some cutting may be required. Keep mouldings for later use.
  • Lift out and remove sash or glass. For hung windows, some cutting may be required.

Clean and prepare the opening
  • Clean the opening of any debris. Cover any holes made by the weight pulleys, etc. Remove any old screen hook eyes or other screws or fasteners.
  • Caulk inside edge of blindstop on top and both sides.
  • Caulk the inside edge of the stool.

1. Protection against air infiltration

To ensure a protection against infiltrations, a flexible water-repellent flashing should be installed on the outside, around the window opening.

2. Place and secure the window

Place the window in its opening and secure it in place using at lease two cedar shims. Use a hammer to install shims around the entire perimeter of the window, every 12 in. Insert single shims under the window to level it. Use a carpenter's level to make sure the window is plumb and level.

3. Fasten the window

Screw the window casing to the frame of the house using long galvanized screws. Drive the screws through the window casing, through the shims and into the framing.
Do not overdrive the screws.

4. Install the dripcap

Install the drip at the top of the window so no water can get behind the window and into the framing.
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