Do I Need a Permit for a Skylight Installation?
Usually yes — installing a skylight cuts roof rafters or trusses, creating a structural opening that needs engineering and inspection. The rare exception: replacing an existing skylight in the same opening (like-for-like). New skylights trigger structural review (the header carrying the cut rafters), energy code (glazing performance), and the flashing details that determine whether the skylight leaks.
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Structural requirements
Cutting rafters interrupts the roof load path — headers carry the cut rafters to the adjacent full rafters (doubled/trimmed). The opening's size determines the header: small curb-mounted skylights (2x2 feet) need modest headers; large skylights need engineered beams. Truss roofs: never field-cut trusses — the truss manufacturer or an engineer must redesign the affected trusses. The skylight curb itself needs structural attachment for wind uplift (skylights are wind-borne-debris and pressure-rated components in hurricane regions).
Energy and glazing
Skylight glazing must meet energy code (U-factor and SHGC — skylights face the harshest solar exposure; low-E and tinted options control the heat gain), safety glazing (tempered or laminated — required over living spaces), and fall protection where required (large skylights need screens or rated assemblies). Tubular skylights (sun tunnels) have lighter requirements — smaller openings, simpler flashing.
Flashing: the leak determinant
Step flashing integrated with the roofing, the curb height (4+ inches above the roof surface typical), and cricket/saddle flashing on the upslope side of wide skylights — these details, not the skylight unit, determine waterproofing. Most skylight leaks are flashing failures. Budget $1,500-$4,000+ per installed skylight; the permit and structural review are a few hundred dollars.
The bottom line
Permit new skylights — engineer the rafter headers (never cut trusses in the field), meet energy and safety-glazing codes, and detail step flashing meticulously.
Torch Engineering PLLC · (480) 490-0064 · info@torchengineering.com — PE stamping backed by Apex Grid Engineering.