Project 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.
Continue to step-by-step instructions
This D.I.Y. Advice is part of a series How To Install a Casement Window

Step by Step Instructions

1 Install waterproof flashing onto the bottom of the casement window frame
2 Mark up and drill pilot holes for the casement window frame
3 Level the casement window
4 Install the casement window
  • Step 1. Install 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.
  • Step 2. Mark 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.
  • Step 3. Level 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.
  • Step 4. Install 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.

Tools and Materials


  • Drill
  • Pencil
  • Ruler
  • Safety glasses
  • Safety gloves
  • Spirit level
  • Staple gun
  • Trimming knife


  • Casement window
  • Masonite packers
  • Plastic flashing

More D.I.Y. Advice

Health & Safety

Please make sure you use all equipment appropriately and safely when following the advice in these D.I.Y. videos. You need to be familiar with how to use equipment safely and follow the instructions that came with the equipment. If you are unsure, you may feel it is safest to consult an expert, such as the manufacturer or an expert Bunnings Team Member.

Grave health hazards are linked to asbestos, which may be in homes built up to 1990. Health hazards may result from exposure to lead-based paints in older materials and copper chromium arsenic (CCA) treated timber. 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. You can also use a simple test kit from Bunnings to indicate the presence of lead-based paint.
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