Curb Mounted vs Deck Mounted

Curb Mounted Skylights

roof slope 0-60

Required for roof slopes less than 14° or 3:12.

curb installation

Curb mounted skylights are the most common skylight type.  This design requires a box structure for the unit to sit on.  Generally this box is comprised of 2×6, or larger, construction lumber set on edge and attached to the roof deck. The box is then ‘flashed in’ with the roofing material for waterproofing.

The skylight is designed to sit over the curb like a lid on a shoe box.  One of the benefits of this design is the ability to replace older skylights without having to re-flash the skylight at the same time.  This can greatly reduce the amount of labor required.  Another benefit is the ease to manufacture custom sizes.   When replacing a skylight becomes a necessity but the flashing is still functioning properly, this is the skylight of choice.  The downside is the higher profile created by the curb and the decreased energy efficiency as most existing curbs are not insulated beyond the 1 ½” thickness of the curb itself.

Deck Mounted Skylights

roof slope 14-60

Suitable for roof slopes equal or greater than 14° or 3:12.

deck install

Deck mounted skylights are a more recent design that lowers the profile of the unit and increases the energy efficiency by ‘hugging’ the roof.  In this design, the curb is the skylight itself.  Higher quality manufacturers, such as Velux, have perfected the art over the last several decades by producing integral flashing kits for various sizes and roofing types.

The lower profile provides a better visual appeal, inside and out, and the increased energy efficiency provides a more comfortable living space and peace of mind. Deck mounted skylights are the choice for new construction or for installing new skylights to existing homes.

2 thoughts on “Curb Mounted vs Deck Mounted”

  1. While it is possible to get a self flashing dome skylight, it is usually a simple job to build a curb and replace the original skylight with a Velux FCM 3030.


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