How You Can Install Your Own Window Frames: A Step-By-Step Guide

Key Considerations Before Starting Your DIY Window Frame Installation

It’s out with the old and in with the new! Whether you're replacing your window frames because they are old, deteriorating, or in desperate need of an update, we’re here to help.

In this article, you’ll learn how to install wooden or aluminium window frames, and the importance of proper installation. Ensuring your frames fit correctly and securely, are weather-tight, and function properly.

Installing Your Window Frames

Installing window frames is a relatively easy task, provided you are removing the existing window frames and replacing them with the exact same size.

Before you begin, you need to know the frame size needed. To do this, carefully measure the existing brickwork opening (hole in the wall) from the outside. Make sure not to measure the existing window frame as it will be smaller than the brick opening.

If the bricks housing the window are plastered over the frame, chip away some of the plaster to expose the bricks to measure accurately. Then, accurately measure the height and width in at least three places and use the shortest measurements.

Tools Needed

Once you’ve accurately measured the brickwork opening, it’s time to start the installation process. This will involve gathering all the necessary tools and materials to get the job done.

1. Safety gear (including gloves, safety glasses and hearing protection).

2. Spirit level to ensure that the window frame is installed straight and that it is level with the wall.

3. Drill and drill bits to drill holes for screws, anchors, or fasteners.

4. Screws, anchors, or fasteners.

5. Screwdriver set (including a Starpoint (Philips), Flathead and different-sized screwdrivers).

6. Hammer to tap shims and adjust during installation.

7. Shims to ensure that the window frames are level.

8. Saw to cut along the window (you can use a milling machine or a reciprocating saw for this).

9. Crowbar to wedge the old window out of the opening.

10. Tape measure to accurately measure the window opening and the frame.

11. Caulking gun to apply sealant or caulk around the window frames for weatherproofing.

Removing The Old Window Frames

For safety and security reasons, ensure that you purchase the new window frames beforehand and check the size before removing the existing frames.

To remove the old window frame, start by putting on your safety gear and enlist the help of someone if the window frame is heavy.

Next, remove any locks, handles, and hinges by unscrewing and completely detaching the opening sashes at the hinges, if applicable.

Scrape out the old putty that holds the glass and remove the small metal glazing nails. Use a chisel or similar tool to chop out the hard putty taking care not to break the glass.

Remove the glass from the frame and put it aside. With the glass and opening sashes removed, carefully remove the old window frame from the brickwork opening. If nails are securing it in place, remove the frame by cutting it out of position. Cut through the transoms and mullions and remove them completely. Then cut through the side jambs at an angle, about one-third of the way up from the window sill, taking care not to damage the internal plaster.

Next, insert a crowbar behind the cut jambs and lever the window frame away from the wall. To reduce damage, place a piece of flat wood between the plaster/brick and the crowbar. This will help to protect the wall surface when pressure is applied.

If your window frames are wooden, get a sufficient grip on the jambs and use your hands to completely pull out the old wooden frame. Remove the head and the window sill in a similar manner, i.e. cutting through and levering away. There may still be horns in the bricks on each side of the opening, just pull them out (they should pull out easily). The resulting holes will need to be filled with mortar mix and cannot be used again.

Finally, check the opening for any remaining nails and traces of old mortar and remove this to leave a clean, clear opening.

Installing Aluminium Window Frames

Start by accurately measuring the window opening and ensuring that it is square and level. Next, clean the opening, making sure to remove dirt, debris and old sealant. Wait for it to dry and make sure the surface is smooth before applying a layer of sealant or caulk to the inside edges of the window opening. Then carefully position the aluminium window into the opening, ensuring that it is level and square. Finally, secure the window in place using screws, anchors or relevant fasteners.

Installing Wooden Window Frames

With the opening prepared, lift the window frame into position from the outside. Leave a gap of about 3mm, top to bottom and side to side between the brick opening and the frame. These gaps are crucial as they allow the frame to be aligned correctly and set squarely.

When setting the window frame into the opening, make sure that the drip groove on the underside of the window sill is clear of the outside wall. Then use wedges to push the frame up against the lintel</a. above. Check that it is level using your spirit level and adjust the wedges if necessary.

The next step is to align the jambs. They need to be perfectly vertical, so use the spirit level on both the outside and inside faces of the window to check if they are vertical. Use wedges to hold the frame in place. Then check that you’ve positioned the window frame correctly by measuring the frame diagonals, keeping in mind that the measurements need to be exactly the same.

Adjust the thickness of the wedges as required to ensure accurate square positioning. Finally, unlatch the opening sashes to make sure that they open easily and secure the frame to the brick using frame fixers, taking care not to distort the frame. Once the frame is securely fitted, use silicone to waterproof it and treat it with a sealer to ensure that no warping occurs.

Browse our other blogs for more useful tips and tricks on doors, windows, and general home improvement and as always, we recommend you speak to a professional if you’re unsure about anything regarding your project.