Should skylights be sealed off during a Calgary reroof?

Skylights should not be sealed off during a reroof; they stay in place and the work happens around them. The real question is whether the existing skylight curb, flashing and interior seal are in good enough shape to last another 15 to 25 years alongside the new shingles, or whether this is the right moment to address them.

What actually happens at a skylight during a reroof

The roofer removes the shingles around the skylight, inspects the curb (the raised frame the skylight sits on) and the step and counter-flashing that directs water away from the unit. Old flashing is almost always replaced rather than reused; reusing it on a new roof is one of the more common shortcuts that leads to a leak within a year or two. If the curb itself is rotted or the skylight unit is cracked, fogged between the panes, or more than 20 years old, replacing the whole unit at the same time as the reroof saves a second mobilisation cost later.

Sealing a skylight shut with roofing material is not a standard practice and would likely trap moisture, void any remaining skylight warranty, and create a future leak point as the sealant ages.

One permit note worth knowing: the City of Calgary says replacing a skylight with one of the same size does not need a permit, but installing a larger or smaller unit requires both a development permit and a building permit. If you are thinking about resizing while the roofers are there, confirm with the City before the work starts.

On the reroof itself, a like-for-like shingle replacement with no structural change does not need a City of Calgary building permit, so the skylight work is typically folded into the same job without triggering a separate application, as long as the opening size stays the same.

Calgary's roughly 128 freeze-thaw cycles a year make skylight flashing a genuine weak point. Water gets under a poorly lapped counter-flashing, freezes, and opens the gap a little wider each winter. Ask each roofer to walk you through exactly how they will flash the curb: step flashing woven with the shingles on the sides, counter-flashing lapped over the top, and a saddle or cricket on the uphill side if the skylight is wide enough to collect debris and snow.

A written quote should spell out whether new flashing is included, what happens if the curb needs repair or replacement (usually priced per unit as a discovered condition), and whether the skylight unit itself is in or out of scope. That way there are no surprises when the old shingles come off.

If you want a few local Calgary roofers to look at the skylight alongside the reroof and give you written quotes, the request form on this site puts the job in front of them.