Skylight Installation with your roofing project

What is skylight installation?

Fitting a skylight means cutting an opening through the roof deck, framing it, setting the unit, and - the part that decides whether it ever leaks - installing the manufacturer's step-flashing kit woven into the surrounding courses of roof covering. That last step is why a roof replacement is overwhelmingly the right moment: the covering is already off, the flashing can be integrated properly rather than retro-fitted around existing material, and one crew owns the whole detail.

How skylight installation actually works

1. 1

   Position it from inside, not from the roof

   Where the light lands in the room depends on the rafter bay available, the shaft angle through the attic, and the roof orientation. The position is settled from below, then transferred up.

   Watch forA location chosen purely for the roofer's convenience between rafters. It is the one decision you live with permanently, and moving a skylight after the fact means patching a roof.

2. 2

   Opening and framing

   The deck is cut and the opening framed with headers so the cut rafters are supported. Where the ceiling is below an attic, a light shaft is built and insulated between the roof opening and the ceiling opening.

   Watch forRafters cut without headers. This is structural work, not carpentry-by-eye, and an unheadered opening transfers load into the surrounding rafters that they were not sized for.

3. 3

   Setting the unit and installing the flashing kit

   The skylight is set on the deck or on a built curb, then flashed with the manufacturer's kit for that model and that roof covering - a head flashing, sill, and step pieces that interleave with each shingle course as the roof is laid up around it.

   Watch forA generic flashing detail or a bed of sealant instead of the model-specific kit. Skylights have a reputation for leaking that is very largely a reputation for being badly flashed, and using the wrong kit usually voids the manufacturer warranty as well.

4. 4

   Sealing and finishing the interior

   The shaft is insulated and air-sealed to the same standard as the rest of the ceiling plane, then finished. Poor air sealing here condenses moisture around the opening in winter, which then gets reported as a leak.

   Watch forCondensation around the frame blamed on the unit. If it appears in cold weather and not in rain, the problem is warm humid air reaching a cold surface - an insulation and sealing issue, not a roofing one.

What does skylight installation cost?

Adding a skylight during a roof replacement is far cheaper than as a standalone job, because access, staging and the surrounding roof work are already in hand. Unit price varies widely by size, glazing and whether it opens. See the skylight cost guide for ranges.

See the full skylight installation cost guide - by material, size and region →

If the number is the problem, here are the ways people pay for it →