What Skylight to Use on a Flat Roof


Flat roofs require numerous specialized considerations – they need protection from strong winds and updrafts, you can’t use standard weight distribution techniques, they need special drainage systems. While flat roofs also require special consideration when it comes to skylights, the skylight industry has taken this into consideration. Numerous types of skylights exist for use on flat roofs, though all of them exhibit certain key design aspects, such as curbs, that help protect your home or building.

Flat Roof Needs

  • Common wisdom holds that a surface must exhibit pitch in order to drain naturally. In this instance, pitch refers to slope; sloped roofs shed water easily because water follows the flow of gravity down the roof. Water can easily build on flat surfaces. On a flat roof, therefore, skylights require special protection to ensure that gathering water can’t leak into your home around the skylight. Skylights also require protection against water collecting on the surface of the skylight, potentially causing erosion.


  • Skylights for flat roofs possess curbs. The curb on a flat roof skylight prevents water from leaking through the skylight into your home. These curbs contain cant strips, or pieces of material used to round out the 90-degree angle at which the skylight and roof intersect. The cant strip helps deflect water away from the juncture of the roof and skylight. Skylight curbs should stand taller than the highest possible level of water accumulation on a roof, according to Carson Dunlop, author of “Principles of Home Inspection.” Dunlop suggests a standard curb height of at least 8 inches for optimal protection. Never install a skylight without a curb on a flat roof.


  • Manufacturers generally design skylights for flat roofs so that water quickly runs off and away from the surface of the material. These designs include domes and architectural forms. Domes constitute any rounded skylights, and vary in shape from slight elliptical curves to circular bubbles. Architectural generically describes any non-rounded, non-flat skylight structure. These range in complexity from simple, small, pitched pieces to large, ornate units like pyramids and boxes with vents and turrets. A pitched skylight is a flat piece of material set at a steep angle, so that water runs straight off of it.

Finding a Flat Roof Skylight

  • A number of manufacturers design skylights specifically for use on flat roofs. You can purchase these skylights directly from the manufacturer or through authorized online or brick and mortar vendors. Before purchasing a skylight for you flat roof, consult a builder on which design works best for your home – this may come down to something as simple as aesthetic considerations, though may also include considerations such as skylight weight, size, shape and structure. For skylight options in your area, contact a local contractor or hardware store, or conduct an online search.

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