VELUX Installation Tips

Before removing VELUX packaging, always check your order to make sure you received the correct products.




Desired area for window

First mark the area where you wish to place the window. Start with a 50cm x 50cm hole in order to access the roof.

 Window area

Remove roof tiles

After making the initial access hole can you then place the removed tiles inside. Make sure you remove the correct amount of tiles necessary for the size of your window.

 Roof tile removal

Now creating the correct size for window

Using 4 Long nails or screws (From outside) you can determine the correct position for your window. Now you can from the inside mark the correct size in order to saw the hole were your window will be placed.


 position roof window

Removing Sash

Once window is removed from packaging, the sash must be removed from the frame. To do this, rotate the sash 165°. Press the locking mechanism on each hinge, for example with a screwdriver. When hinges are disconnected, place sash on a clean and even surface with the top end on the ground.


 Removing Sash

Installing Battens

Before you can set the frame into the roof, you must first install two battens. Place the lower batten at 8cm from the upper side of the roof tiles. For the placement of the upper batten measure the height of the external frame size and add 45mm to measurement.


 Installing battens

Installing insulation collar BDX

For good insulation we recommend the BDX, it is important that you add approx. 2-3cm at each side of the external frame size. Before installing the window frame, position the insulation collar on the mounted battens, in order to fill the space between frame and roof opening. The BDX insulating collar is a perfect solution for insulation between the window frame and the roof. (BDX insulating collar comes with the underfelt collar BFX).


 Installing BDX

Installation of VELUX Window frame

Slide the mounting brackets into the prepared mounting groove of the frame and screw it down. Then place the frame with four mounting brackets on the two battens. The brackets must be fitted to the frame prior to positioning of the window in the roof. See also the supplied installation instructions.


 installing Wwindow frame

Underfelt collar BFX

Fix the underfelt collar to the frame on all sides, shape it around the battens and fix it to the counter battens. Position the drainage gutter above the upper batten, so that any water from the underfelt runs into the gutter.


 underfelt collar BFX

Flashings and Covers

Fit flashing and covers in the sequence as indicated in the instruction manual for the window and the flashing respectively. The individual parts have a number on the back that in most cases also indicates the installation sequence. Note that there are left and right parts.


 Flashing and covers

Replacing Sash


Before replacing sash, we advise you to use a cloth, or piece of cardboard to protect the window frame. Place sash in at a 180° tilted angle through the opening, and secure the bottom of the frame with the barrel bolt. Gently place the sash hinge arms back into the frame counter hinges. When the window is closed, the locking pins on the hinge arms will engage automatically.
 Replacing Sash

Vapour barrier collar BBX

The easiest solution to restore the air tightness, and to protect your roof from condensation.

Fit the BBX foil into the window frame rebate. Then apply, by means of the supplied tape, the foil to the inside of the roof construction of your ceiling.


The VELUX BBX Vapour Barrier is not strictly necessary for the installation of your roof window. However, VELUX do recommend the installation of the vapour barrier, to prevent condensation and moisture damage in your roof construction.


If you’ve purchased a VELUX LSB interior ceiling finish, then you will automatically find the VELUX BBX vapour barrier included in the LSB packaging.

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