The size or dimension of the skylight itself is based upon the outer dimensions of the mounting curb or support structure. When measuring the curb, it is important to ensure that you measure to the outermost part of the curb (also known as out-to-out of curb). It is equally important that the curb itself be square (i.e. equal and parallel sides) and level. To ensure that your curb is square, measure the diagonal distance from each opposing corner. If the dimensions are not equal, than the curb is not square and must be modified prior to installing the skylight. Once you are confident that the curb is square and you have verified that the outer dimensions are correct, you may enter those dimensions into the spaces provided in Step 2 of the Design Your Skylight section.

Note: The mounting curb must be a minimum of 6 inches wide and be constructed to withstand the design loads produced by the weight of the skylight itself and any existing weather conditions (snow / wind). Specific design load support reactions are called out on the detail drawings, which may be downloaded at the completion of each design session. A steel or concrete curb is required for skylights larger than 10 feet in width.

Curb Layout for Pyramid, Ridge, Hipped Ridge and Polygon (similar)

Curb Layout for Ridge Skylight with Jamb Condition
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