Mastering Roof Inspections: Roof Penetrations, Part 5

by Kenton Shepard and Nick Gromicko, CMI®



The purpose of the series “Mastering Roof Inspections” is to teach home inspectors, as well as insurance and roofing professionals, how to recognize proper and improper conditions while inspecting steep-slope, residential roofs. This series covers roof framing, roofing materials, the attic, and the conditions that affect the roofing materials and components, including wind and hail.  



You’ll see skylight flashing installed using a number of methods, depending on the age of the type of skylight, the type of roof-covering material, and who installed it.


Self-flashed skylights come from the factory with flanges that fit against the roof. The flashing kits that come with them are relatively simple to install.


Curb-mounted skylights are mounted on a curb built from 2x4 or 2x6 on edge, as you see here.

Flashing kits are available for standard-sized curbs or flashing, and may be hand-fabricated, as this was.

Looking at a few key points will tell you about the quality of the installation. Above the skylight, shingles or slate should stop an inch or so short of the skylight itself to create a melt-water channel.

At the two uphill corners, the flashing should extend past the corner at least 1/8-inch. The type of flashing used on the sidewall and downhill sides of the skylight will depend on the type of roof-covering material installed.

As always, you'll be watching for and commenting on any broken skylights.


Various types of mechanical equipment installed on roofs have fasteners that penetrate the roof-covering material. Some examples are:


braces for chimneys,


air-conditioning equipment,


photovoltaic panels,


solar thermal panels for hot water,

satellite dishes,

and attachments for patio covers.

Basically, anything that penetrates the roofing is a potential entry point for moisture and should be looked at closely, both on the roof and from inside the attic, when possible.

Penetrations should be well-flashed and/or sealed.  Again, anytime a sealant is used, it will eventually dry, shrink, crack and may leak, so each penetration is another potential area of leakage.


Learn how to master a roof inspection from beginning to end by reading the entire InterNACHI series: Mastering Roof Inspections.

 Take InterNACHI’s free, online 
Roofing Inspection Course
Mastering Roof Inspections
Roofing Underlayment Types
Inspecting Underlayment on Roofs
Fall-Arrest Systems
Roofing (consumer-targeted)
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