Should my new Calgary roof get synthetic underlayment?

Synthetic underlayment is worth the upgrade on a Calgary roof, and most roofers here will quote it as their standard product. The cost difference over felt is modest, typically a few hundred dollars on a full replacement, and the performance gap in this climate is real.

Why Synthetic Makes Sense Here

Calgary's roughly 128 freeze-thaw cycles a year, combined with chinook winds that can lift and crease shingles, put underlayment under constant stress. Synthetic underlayment is lighter, tears far less during installation, and holds up better when shingles are temporarily lifted by wind. Felt, especially the lighter No. 15 grade, absorbs moisture, wrinkles when wet, and can dry out and become brittle in Calgary's low humidity. Synthetic products resist both problems.

That said, underlayment is only part of the water-management picture. The National Building Code (2023 Alberta Edition) requires eave protection on shingle, shake and tile roofs: a self-sealing modified bitumen membrane (ice-and-water shield) or an approved alternative, running at least 900 mm up the slope and to a line at least 300 mm inside the inner face of the exterior wall. In Calgary, with its degree-day count, the mild-climate exemption does not apply, so this strip is mandatory. Synthetic underlayment runs above that eave protection layer, covering the rest of the deck.

The City of Calgary also recommends continuous ice-and-water shield over the entire roof deck to combat ice dams, which is a step beyond the code minimum. On a house with a history of ice damming or poor attic ventilation, that full-coverage approach is worth discussing with your roofer.

A permit is not needed for a like-for-like shingle replacement in Calgary, so the underlayment choice does not change the permit picture. If you are switching materials entirely, confirm with the City of Calgary before signing.

When you are comparing quotes, ask each roofer to specify the underlayment product by type and weight, not just "synthetic." Ask whether ice-and-water shield is included at the eaves only or over the full deck, and what the per-sheet price is for any decking replacement discovered once the old roof comes off. A quote that bundles everything into one line without specifying materials is harder to compare fairly.

If hail is part of the reason you are replacing the roof, ask your insurer before you sign anything. They may have requirements or preferences about the shingle class, and some offer meaningful premium reductions for Class 4 impact-resistant products. Your insurer is the right first call, because what they cover and what discount they offer should shape the product conversation with your roofer. Once you know where you stand on coverage, the request form on this site reaches local Calgary roofers who can put the underlayment spec in writing.