Xtralite and Vitral are now a part of VELUX Commercial, and we are delighted to welcome you to our new website. Here, you will find our complete portfolio of daylight solutions and services for industrial, commercial and public buildings.


A hassle-free installation starts with the sub-construction.

The sub-construction raises the modules above the roof surface, protecting the structure against water and drifting snow. The sub-construction provides the supporting base for the modular skylights.
The skylight modules require an accurately dimensioned sub-construction, which can carry the module installation system.
The load-bearing capacity of the sub-construction needs to be calculated for each individual project based on the building design and application.
The sub-construction is not part of the prefabricated modular system, and the VELUX Group does not take responsibility for the sub-construction.

Sub-construction for VELUX Modular Skylights

Sub-construction material


Sub-construption in timber
Wood remains the best choice for creating a light and economical sub-construction with maximum energy performance. Wood is not recommended for larger solutions and Ridgelight installations.


Sub-construption in steel
Steel offers flexibility in combination with great strength. Steel also permits maximum insulation.


Sub-construption in concreate
Concrete provides a strong, but heavy sub-construction, best suited for concrete buildings. Concrete sub-constructions are usually cast on site.

Securing modular skylights to the sub-construction

Using steel profile or flat steel

The top of the sub-construction should be finished with a steel profile or flat steel to provide a strong and level surface as the base of the installation brackets with clamps.

Steel profile on timber
Flat steel on wood
Steel profile on steel
Steel profile on steel
Steel profile on concreate
Flat steel on concrete
Wood profile on timber
Wood profile on wood is not recommended by VELUX Commercial.