You bought a skylight at Brico Dépôt and the box has been sitting in the garage for two weeks. The hold-up isn’t the weight of the glazing or the installation cost: it’s often the fear of doing it wrong. Preparing the site methodically, identifying the pitfalls before climbing onto the roof, and using the markers provided with the product turn this operation into a project accessible to any organized DIY enthusiast.
Factory Markers and Brico Dépôt Instructions: What’s Really in the Box
Before touching the framework, open the box and lay out each element on the ground. The latest ranges of skylights sold in DIY stores, including Brico Dépôt, include brackets and pre-positioning markers marked at the factory. These marks help to position the frame at the correct height without measuring from the inside with a laser meter.
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The recommended height places the bottom of the window between 90 and 110 cm from the finished floor, depending on the use of the room. The engraved markers on the frame correspond to this range. If you ignore them, you risk installing the window too high (loss of view to the outside when seated) or too low (risk for children, non-compliance).
For a few years now, Brico Dépôt has offered direct downloads of the specific installation instructions for the brand and model on each online product sheet. This PDF document specifies the exact dimensions of the frame to be created, the lateral gaps to respect, and the orientation of the waterproofing flap.
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Download it before purchasing: it will allow you to check that the spacing of your rafters matches, and avoid a return to the store. When looking to install a Brico Dépôt skylight easily, this step of technical reading saves several hours on the day of installation.
Frame and Roof Cutting: Costly Mistakes
The frame is the wooden structure you create in the framework to accommodate the window. It’s also the stage where most mistakes occur.
Check the Structure Before Cutting
You may want to mark and cut quickly. First, take the time to identify the type of framework. A traditional framework with purlins and rafters allows for more freedom than an industrial framework with trusses. On trusses, cutting an element without prior reinforcement weakens the entire structure.
In both cases, the frame must be secured with screwed metal brackets (not just nailed). The brackets can be found in the framework section of Brico Dépôt for a few euros, and they ensure a rigid connection between the wooden pieces.
Cut the Covering Without Breaking Neighboring Tiles
Remove the tiles or slates one by one from top to bottom. Slide a flat tool under each element to detach it from the batten without forcing on the adjacent rows. Keep the elements intact: you will need them to close the edges around the frame.
- Identify the battens to keep and those to cut by marking them with a thick pencil before any cutting.
- Protect the inside of the attic with a tarp stretched under the work area, as debris will inevitably fall.
- Work in dry weather: a damp framework makes supports slippery and wood more difficult to screw cleanly.
Waterproofing and Covering Connection: The Detail Most Guides Overlook
The window is in place, the glazing shines. But the waterproofing is determined in the ten centimeters around the frame, not in the frame itself. It’s the connection between the frame and the covering that determines whether your Velux will last ten years without leaks or if signs of moisture will appear after the first serious storm.
Each skylight comes with a connection kit (called “collerelle” or “EDP/EDW kit” depending on the brand). This kit includes pre-folded lead or aluminum flaps. The installation order is strict: lower flap first, then side flaps, then upper flap. Reversing the sequence creates capillary rises between the layers.
Have you noticed those little adhesive tabs on the flaps? They are not meant for permanent adhesion. They hold the piece in place while you reposition the tiles over it. The final hold depends on the overlap of the tiles over the flap, not on the adhesive.
Summer Comfort and Dimension Choices: A Often Overlooked Parameter
Since the implementation of RE2020, the requirements for summer comfort have changed the game for skylights. A skylight that is too large facing south, without external solar protection, can turn converted attics into saunas as early as June.
This parameter does not only concern new constructions. If you are installing a skylight as part of an extension or a height increase subject to a building permit, the regulatory calculation includes the glazed area on the roof and the solar factor of the glazing. Poor sizing can compromise the RE2020 compliance of the project.
Specifically, two reflexes help limit overheating:
- Choose glazing with enhanced solar control rather than standard double glazing, especially on south and west orientations.
- Plan for the location of an external roller shutter during installation. Brico Dépôt offers autonomous solar kits that do not require any electrical connection.
- Reduce the glazed area if the room is small: a narrower window placed well provides as much light as a large poorly oriented window.
Brightness is not just about the size of the opening. The height of installation, the angle of the slope, and the color of the interior walls play as much of a role as the dimensions of the glazing. It’s better to have a properly sized skylight, installed at the right height with a watertight connection, than an oversized model that requires a blackout blind for six months a year.