Everything you need to know about replacing roof windows


Thinking about replacing your roof window but don’t know where to start?

Don’t worry – we’ve put together this guide to everything you need to know when it comes to replacing your roof windows.

Do I need to replace my roof window?

If properly maintained, roof windows can last anywhere between 20-40 years.

Although there are a couple of signs that your roof window might need replacing, including damage and wear to the window or frame.

If your window is starting to let water or moisture in (which might look like mist caught in between the layers) it could start to cause structural damage to your home and will need replacing.

You don’t need to wait until the end of a roof windows life to replace it though. For those who want the benefits of a newer window, including better energy efficiency, go ahead!

Should you replace roof window

How easy it to replace my roof window?

A lot has changed over the years, but window sizes haven’t.

Roof window replacement is a straightforward process. Simply choose a window that matches the current size of the one you have, and you’re set! It’s so easy to do and doesn’t make any structural changes to your roof or opening.

Windows can be replaced within 4 hours, making them great projects for both beginner and advanced DIY-ers. But, don’t worry – you can hire a professional if you prefer.

You don’t need to worry about planning permission for Velux windows or replacement roof windows. As the original windows will be compliant with roof regulations.

What is the cost of replacement windows?

The cost of replacement windows depends on the size and type of window that you want.

Typically, the cost for the window, flashing and installation can vary between £700-1000, but if you’re installing the window yourself it’ll be slightly cheaper.

Replacing a roof window

How do I replace my roof window?

Want to replace your roof window yourself? Follow these simple steps for a quick and easy installation.

Step 1: Remove the opening sash from your window. How this works depends on the model of your window, but is typically done by opening the window and pushing in the pins on the hinges.

Step 2: Remove the tiling/slates from around the roof window. Make sure that you are careful to save the tiles, as they’ll be put back on the roof when the new window is installed.

Step 3: Remove the flashing and the frame. Once the old window is gone, it’s time to install the new one.

Step 4: Following the instructions, remove the opening sash from your new window. Once removed, install and secure the new frame into the opening in your roof.

Step 5: Fit the flashing. Because flashing is the important tool that protects and weatherproofs your window, it’s important to take the time to get this step right

Step 6: Return the tiles/slates to the roof. Because you’ve used the same opening, the tiles should fit the same as before without having to be cut down or resized.

Step 7: Fit the opening sash back to the frame and enjoy your new window!


The process of replacing a roof window is a lot easier than you might think.