One of the most important steps when installing a skylight is to also install metal flashing. This flashing is a thin sheet of material that is bent in a way that it wraps around the contour of the hole the skylight will be installed in. There is generally an L-shape to the flashing to form a better seal. Many homeowners make the mistake of skipping this step and installing a skylight without this important piece of protection. Why is flashing important?
Protects Underlying Frame
The flashing is used to protect the underlying wood frame from dampness. When it rains the water can run along the seam of the skylight and find a small area where it can leak into the interior. The flashing provides a barrier in between the wood frame of the ceiling and the skylight. It is installed with about 6 inches extended to keep water from flowing into the roof.
Seals around Fasteners
Another problem area when installing a skylight is the fasteners that are used. When driven into the wood roofing, fasteners create a hole that water can seep through. Some newer flashings that use a tar-like material actually seal around the fastener. This creates a watertight bond, and a stable place to start your nail or screw.