One size matters: the daylight size.

You always order a skylight or flat roof window by daylight size: the clear opening at the top of the curb. The curb is the raised edge on your flat roof on which the skylight rests. The size of the opening in your roof depends on that curb.

Side view: daylight size, roof opening and height

Example: a sloped curb 16/20. It is 16 cm high and the roof opening is 20 cm larger than the daylight size. The daylight size is the opening at the top: the size you order. With a straight curb, the roof opening equals the daylight size.

Top view: how to measure the daylight size

Do you already have a curb? Measure the clear opening at the top, in width and in length. Do not measure the outside of the curb. Only the opening on which the skylight or flat roof window will sit counts.

Which size do you order?

That depends on your situation. Replacing a skylight or flat roof window? Then start from the daylight size of your current curb. Creating a new opening? First choose the daylight size, then adapt the roof opening to it.

You already have a Skylux curb

Measure the clear opening at the top of your curb: width × length. That is your daylight size. This is the size you order, for a skylight and for a flat roof window.

You are creating a new roof opening

First choose your daylight size. Then make the roof opening to size. With a straight curb, it equals the daylight size; with a sloped curb, it is larger.

You have a curb from another brand

No problem. With a renovation frame, you can install a new Skylux skylight or flat roof window on your existing curb. No demolition work required.

How big is the skylight itself?

Around the skylight is an 8 cm flange that rests on the curb. The skylight is therefore 16 cm larger than the daylight size: 8 cm on each side. A skylight with a daylight size of 100 × 100 cm therefore measures 116 × 116 cm.

Roof opening by curb

How large you make the hole in your roof depends on your curb.

Vertical curb

Roof opening = daylight size

A vertical curb runs straight down. As a result, the opening at the top is the same size as the hole in your roof. So the roof opening is equal to the daylight size.

  • 16/00: 16 cm high · roof opening = daylight size
    Suitable only for skylights, not for flat roof windows.
  • 20/00: 20 cm high · roof opening = daylight size
    Suitable for skylights and flat roof windows.

Discover straight curbs

Sloping curb

Roof opening = daylight size + extra

With a sloping curb, the walls slope outward. As a result, the opening at the bottom is larger than the daylight size. So the roof opening is equal to the daylight size + extra.

  • 16/20: 16 cm high · roof opening = daylight size + 20 cm
  • 35/30: 35 cm high · roof opening = daylight size + 30 cm

Discover sloped curbs

The curb code

How to read the code

The curb code shows the height and the roof opening.

  • 20/00: 20 cm high, roof opening = daylight size.
  • 16/00: 16 cm high, roof opening = daylight size. Only for skylights.
  • 16/20: 16 cm high, roof opening = daylight size + 20 cm.

E.g. with a daylight size of 40 × 40 cm, the roof opening with 20/00 or 16/00 is also 40 × 40 cm. With 16/20, it becomes 60 × 60 cm.

All about curbs

Find your size

Explore the range and order directly by daylight size.