How to replace glass windows?

Are you planning on replacing the window glass yourself? Whether you’re replacing a wooden window or one with a plastic frame, follow our simple step by step instructions to make a success of this DIY project.

Requirements for a diy window replacement:

The material for making a diy window replacement

In this DIY blog, we’ll take a new barn door without a window as our example so we don’t need to remove the glass slats. We’ll be using budget plexiglass (extruded) to replace the window glass, and we can cut it to the exact size you need for free. If you want to cut the plexiglass yourself, then we recommend choosing clear cast acrylic sheet 20 mm thick. If you would like more privacy, opt for frosted acrylic sheet.

The difference between extruded and moulded acrylic lies in the production process. Extruded or cheap acrylic sheet is rolled to the desired thickness after casting. The process creates tension on the sheet and makes it more liable to break. This means it’s harder to machine than the moulded version. Cheap acrylic sheet is the economical choice if you need glass for applications that are not heavily used, such as a barn door window in our example.

1: Remove the glass battens

To decide on the size of the window acrylic that you need to order, first remove the glass battens from the window that you want to replace. You need to measure the rebate size or the space in the frame without the glass battens. Remove the glass battens using a chisel or a screwdriver to prise them out.

2: Measure the window

Measure the window and subtract 2 mm all round. This is to allow for the plexiglass expanding as the temperature rises.

Replace a window glass measure rebate size

3: Apply glass tape

Apply glass tape around the frame, 2 mm away from the edge. Then stick glazing tape on the back of the glass battens, once again 2 mm from the edge.

Window replacement placing the glass band

Window replacement placing glass band on the glass battens

4: Position the window

Fill in the rebate with filler plates approximately 3 mm thick, also known as glass cubes. Next position the plexiglass window in the frame.

Replace a window glass attach acrylic sheet

5: Attach the window battens

Next, it’s time to attach the glass battens. Use a drilling machine for this task.

Replace window drilling glass battens

Window replacement attaching glass battens

6: Finishing the window

Give your plexiglass window a neat, secure finish with glazing glue. Do this at both the front and the back of the window. Make sure that the glue is also applied between the windowpane and the glass battens. Clean your window using warm water and a few drops of Burnus plastic cleaner and voila: your diy window replacement is complete!

Shed window replacement result
DIY window replacement result

Replace a half-moon window

Do you have a small circular window that you want to replace with plastic? Now you can order custom perspex shapes in a range of thicknesses from our webshop. The options vary from replacement glass for a hexagon window to custom round window glass. Select your diameter on the product page for the type of acrylic sheet you require and we’ll laser cut the shape to size for you.

Order plexiglass for your diy window replacement

Are you intending on replacing a window yourself soon? When you order window perspex from us, we’ll saw the customized sheet for you free of charge and we’ll send your order as soon as possible.

Looking for more DIY inspiration?

View our blog for more fun and easy DIY projects. If you need any more information about replacing a window or about our products, please feel free to contact us.