Does your building have a skylight? Are you considering adding a skylight? In either case it is important to understand the basic types, installation, and problems that result from improper installation.

Types:
There are two basic types of skylights for residential construction: curb mounted or frame-in-place, also called self flashed. Curb-mounted skylights are typically raised above the deck on a frame and are more suited for low pitch roofs. Frame-in-place skylights are surface mounted directly to the roof deck. Other types of skylights include commercial installations or architectural skylight systems, which are much more involved, less generic in nature, and are designed specifically for the roof assembly and architectural objective.

Installation:
There are several basic components to skylights which are critical in understanding your particular application and avoiding a problematic installation. The components are the base frame, which is usually aluminum; the top sash frame, which is also usually aluminum; the glazing, which is usually glass, acrylic, or polycarbonate; the flashing, which can be metal or self-sealing and flexible; and the gaskets, which are most critical when the skylight is operable. The glazing will likely be flat insulated glass or double dome construction for non-glass to ensure energy efficiency.

Problems:
Obviously water leaks are the most common symptom when problems arise. Therefore, manufactures instructions should always be followed for installation of the skylight and flashing components. Regardless of the type of flashing supplied, always use a peel-and-stick flashing membrane to seal the unit to the deck before the underlayment and shingles are re-applied. One less common problem observed around skylights is condensation and ensuing mold. Unless the unit is supplied with an insulated light shaft/tube, a chase will likely need to be constructed of drywall, which must be properly insulated in the attic to avoid mold growth on the drywall surfaces and ceiling.

If you need help with a skylight installation issue or other roofing problem, our Building Envelope group is ready to assist you. Please contact Steve Towne at stowne@brackenengineering.com.

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