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How to install a casement window

A Bunnings team member installing waterproof flashing onto the bottom of the casement window frame

Overview

Casement windows are a great way to bring light and air into a room. We show you how to install one into a wall opening. You will also learn how to install a waterproof flashing barrier under the frame and a simple way to level the frame up using masonite packers.

Steps

1Install waterproof flashing onto the bottom of the casement window frame

Staple a strip of waterproof flashing onto the rear of the window frame so it can fold underneath and cover the base. Be sure to leave yourself plenty of overhang on either side. Staple that overhang tightly into position onto the sides of the window frame. This holds the flashing in place but leaves it loose at the front of the frame.
A Bunnings team member installing waterproof flashing onto the bottom of the casement window frame

2Mark up and drill pilot holes for the casement window frame

Mark up and drill pilot holes near the top and bottom of the sides of the window frame. The holes should be about 40-50mm back from the window jamb and 75-100mm from the top and bottom of the frame. The width of the hole should match the width of the shank of the screw.
Drilling pilot holes into the window frame

3Level the casement window

Place the window into the wall opening. If it is a heavy window, get someone to help you with this step. Use your spirit level to check that the window is level. If the window is not sitting exactly plumb, level it up with masonite packers. Then use your ruler to make sure the frame is sitting flush with the internal walls.
Using the spirit level to check the window is level

4Install the casement window

When you are sure the frame is sitting in the proper position, drive screws through the pilot holes and into the frame of the house. To give your job the best finish, countersink your screws so they sit below the surface of the timber. That way you can cover them with putty before you paint.
Drilling screws into the pilot holes to install the casement window
Health & Safety

Asbestos, lead-based paints and copper chromium arsenic (CCA) treated timber are health hazards you need to look out for when renovating older homes. These substances can easily be disturbed when renovating and exposure to them can cause a range of life-threatening diseases and conditions including cancer. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer or visit our Health & Safety page.

When following our advice in our D.I.Y. videos, make sure you use all equipment, including PPE, safely by following the manufacturer’s instructions. Check that the equipment is suitable for the task and that PPE fits properly. If you are unsure, hire an expert to do the job or talk to a Bunnings Team Member.