How to Fit a Velux

Updated April 17, 2017

Velux is a term that can be used to refer to energy-efficient roof windows that are manufactured and marketed by Velux, a company that develops products that allow and control daylight and fresh air in buildings. Velux roof windows are designed to add natural light and air to a home or business. The windows may also minimise noise transmittance and heat loss.

Inspect your roof top to find a suitable location that can fit the dimensions of the Velux window you have with the least amount of removal needed from the existing roof structure. Position the Velux window so that the surrounding roof support structure (purlins, rafters, and struts) will not be weakened after fitting the window.

Prepare the Velux window opening. Remove enough tiles or slates from the roof area you identified. Cut away one of the battens from under a tile/slate with a jigsaw and slide the tile out, and do the same for other tiles until enough tiles are removed. Use a jigsaw to cut away the necessary roof timbers to the correct Velux window dimensions as shown in the Velux installation instructions that come with the Velux package. Do not cut the Velux window opening wider than the Velux width plus two inches. You may need to cut an opening in between rafters, just big enough for you to stand and work in, if you have a ceiling in between the roof where you want to fit the Velux.

Strengthen the roof timbers that remain after creating the Velux opening. Make a new framework around the Velux window opening by adding additional timbers around the opening.

Install the Velux window. Remove the Velux opening sash (opening section) of the Velux window and fit the Velux window using its pre-fitted straps and the fixing brackets supplied with the Velux window package. Mold roof flashing to tile shape and apply on the window opening. The roof flashing keep the joints between the Velux window frame and the roof watertight.

Re-install the roof tiles/slates into position. Position roof tiles/slates up to the sides of the installed Velux frame. Cut the tiles/slates with an angle grinder to shape them into the Velux window frame. Mark the tiles that need to be cut into position, move them to the ground, cut them from the ground and then fit them into position against the Velux window frame. Wear safety goggles when using the angle grinder.

Replace the Velux opening sash. Follow Velux opening sash fitting instructions and reinstall the opening sash on the Velux window to finish fitting your Velux window.


Always observe your local area building regulations and planning permission before fitting a Velux. Contact the building control department of your local council or appropriate government representatives to obtain clearance.


Due to the safety risks involved with working on a roof, do not perform the task by yourself if you are not a professional. Seek the services of a licensed roofer to fit your Velux window safely.

Things You'll Need

  • Jigsaw
  • Safety goggles
  • Angle grinder
  • Hammer
  • Saw
  • Ladder
  • Measuring Tape
  • Nails
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About the Author

David Kiarie has been an independent writer and communications practitioner since 2007. Based in Africa, he has written works that have been published in various platforms, including "Prime Scope Magazine." Kiarie particularly enjoys writing about Africa, including African travel and art. He has a Bachelor of Arts in language and communication and literature from the University of Nairobi.