How to install a Velux

A roof window is commonly referred to as "Velux" here in Belgium, indicating how popular this brand is. If you want to find out how to install a Velux in your roof, read on.



The story begins with the plan to have some daylight in my study. Researching the website of Velux revealed an astonishing selection of models and sizes. In the end, I opted for a big 78cmx140cm centre-pivot window.



The website conveniently lists all of the installation accesories available:
- The flashings kit to ensure rain ends up on the roof and not in your room
- The underfelt collar that sits beneath your roofing material
- The insulation frame that ensures no cold bridges can exist
- The vapour barrier that shields the inside finish of your room from moisture in and below the isolation.
- The finishing kit.



Installation went smoothly thanks to the clear pictures in the manuals. The fact that I could download the manuals from the website meant that I could plan ahead. What was a bit of a bummer is that Velux does not let you order their installation products and windows online. You can only order curtains online. This meant for me that I had to go to a shop, try to explain to the employee in a DIY shop what product numbers I needed and had to go into an argument with this "professional" on why I wanted to order "unnecessary parts" like the underfelt collar and isolation frame.



The steps I took where:
- make a small hole of 50cmx50cm so I could access the roof from inside the room
- determine the final location of the window based on where the structural supports of the roof are
- take away the roofing material, underfelt and isolation from the outside
- attach the supporting bar using a spirit level
- mark the lower 2 corners of the window on the supporting bar.
- using a straight edge and a triangle, find the top 2 corners of the window.



Here comes a little trick: if you only want to have to cut the finish on the inside of your room in the perfect place, you can transfer the measurements made on the outside to the inside of the Gyproc by turning a screw to go through the Gyproc.
You can then draw lines between the 4 scvrews on the inside of your room and make a perfect cut without having to retouch later on.



When you have removed the inside finish of the room (Gyproc, in my case) you can remove the rest of the wood and reinforce the roof in places where you removed structural elements.



Once the hole is made, all of the accesories and the window itself can be installed by the book, there really is nothing to it. Especially the inside finishing kit is marvelous: no "wet" finishing, sanding or painting is required. You just saw the finishing kit along the indicated lines (sawing lines will not be visible after installation), screw the parts together and snap into place on the window.

All in all happy with my window, installed in 1 day with professional result.