Asphalt Shingles for Northwestern Ontario: What to Look for in the Spec

Most quotes for a Thunder Bay re-roof list the shingle by name and colour, and that is about it. The brand on the wrapper matters less than what is on the spec sheet behind it. Wind rating, ice-and-water membrane, shingle weight, granule quality, and the warranty tier you actually qualify for are what decide whether your asphalt roof lasts twelve winters or twenty-five. Here is what to look for, and what to push back on.

A quick note up front. Asphalt is still the most common roof in this city, and a well-specced asphalt roof is a sound choice on the right home. The point of this guide is not to talk you out of it. It is to make sure the asphalt roof you buy is built for this climate, not for Southern Ontario.

Architectural vs 3-Tab: Stop Buying 3-Tab Up Here

A 3-tab shingle is a single, thin layer. An architectural shingle (also called laminated or dimensional) is two bonded layers and a thicker profile. For Thunder Bay, the answer is architectural, almost always.

Why:

• Wind resistance. 3-tab shingles top out at lower wind ratings and lift more easily on exposed lots and lakeside homes.
• Lifespan. Architectural lasts noticeably longer in our climate, often by five to ten years.
• Snow and ice tolerance. The thicker, heavier profile handles freeze-thaw cycles and ice forming under the edges better than a thin 3-tab.

The price difference per square is real but not huge once you factor labour, tear-off, and disposal, which are the same either way. If a quote shows 3-tab on a Thunder Bay home, ask why, and ask what architectural would cost. Nine times out of ten, the better roof is worth the upgrade.

Wind Rating: Look for 110 mph or Better

Lake Superior wind is the wear-and-tear nobody factors in when they shop a shingle by price. Off the lake, gusts hit exposed roofs hard, especially on homes in Shuniah, the north shore, and the rural sections of Oliver Paipoonge and Neebing. What lifts a roof is not the average wind, it is the gust at the wrong angle.

Look for shingles rated to at least 110 mph (about 177 km/h). Premium architectural lines go higher. The rating depends on the installation, which is a polite way of saying: the rating only applies if your roofer nails them correctly, in the right pattern, with starter strip at the eaves and rake edges. A good crew will know all of this. A bad one will not.

Ice-and-Water Membrane: Required Here, Not Optional

If your quote does not include ice-and-water membrane at the eaves and valleys, it is not a roof built for Thunder Bay. Period.

Ice-and-water membrane is a self-adhering rubberized layer that goes under the shingles. It seals around the fasteners. When an ice dam forms and meltwater backs up under the shingles (which it will, eventually, on any home), the membrane stops the water from reaching the decking. Without it, that water goes into your plywood, insulation, and ceilings.

What to look for in the spec:

• Coverage at the eaves. The standard is to run membrane up the roof past the wall line. Ask how far. Three feet up from the eave is a typical minimum.
• Valleys. Full coverage through every valley.
• Penetrations. Around chimneys and roof penetrations is standard practice on a real install.

We treat this as baseline, not an upgrade. More on the mechanism in our ice dam prevention guide.

Underlayment: Synthetic, Not Felt

Old-school felt paper still shows up on cheap quotes. Synthetic underlayment is the right call. It is tougher, lighter, does not tear under foot traffic on the install, and handles moisture better. The cost difference is small. If a quote specifies 15-pound or 30-pound felt as the field underlayment, ask about synthetic.

Shingle Weight and Granule Retention

Heavier shingles, within reason, tend to hold up better. Weight per square (100 square feet) is one rough proxy for durability, though it is not the only one. Two shingles at the same weight can perform differently based on granule quality.

Granules are the coloured ceramic chips that protect the asphalt from UV. Lose the granules, lose the roof. Look for shingles with high granule retention ratings and a manufacturer with a long track record. Cheap shingles shed granules fast in the freeze-thaw cycles up here, which is why you see the dark, bare patches on aging roofs by year ten. A quality architectural shingle will hold its granules for the full lifespan.

The Warranty Tier (and the Trap)

Most major manufacturers offer tiered warranties. The headline number (like “50-year”) gets you in the door, but the actual coverage depends on:

• Whether the installer is certified by that manufacturer
• Whether the full system was installed (their starter, ridge cap, underlayment, ventilation)
• Whether the warranty is registered after install
• How the proration works as the roof ages

A non-certified installer using a single-product approach often qualifies your roof for the basic limited warranty only, which is much shorter than the headline. Ask which warranty tier you actually qualify for given the installer, and get that in writing. We get deeper into this in our warranty guide.

Why the Cheap Spec Costs More

Here is what we see often on a Thunder Bay home that was re-roofed cheap eight to twelve years ago: 3-tab shingles, felt paper underlayment, minimal or no ice-and-water membrane, ventilation untouched. The roof looked fine for a few years, then ice dams started, then granule loss, then leaks at the eaves. The owner is now paying for a full replacement of a roof that should still have a decade of life.

A proper spec on the same home would have cost a few thousand more on day one. It would still be doing its job.

What a Good Spec Looks Like

A solid asphalt roof for Thunder Bay, in plain terms:

• Architectural shingles, 110+ mph wind rating, from a known manufacturer
• Ice-and-water membrane at all eaves (well past the wall line) and through every valley
• Synthetic underlayment across the full deck
• Manufacturer’s matching starter strip at eaves and rakes
• Matching ridge cap (not field shingles cut into caps)
• Corrected attic ventilation, balanced soffit intake and ridge exhaust
• New flashing at chimneys, vents, and walls
• Documented manufacturer warranty at the proper tier, plus a written workmanship warranty

That is the build sheet we use on every shingle install. You can see it in detail on our shingle roofing service page.

When to Talk Metal Instead

If you are weighing asphalt against metal, the spec changes the math. A premium asphalt roof installed properly will last twenty years up here, give or take. A metal roof lasts forty to seventy. The comparison is laid out honestly in our metal vs asphalt guide, and the roof cost calculator gives you a quick ballpark for both.

A well-specced asphalt roof is still the most common choice in this city, and for many homes it is the right one. Just buy it knowing what should be on the spec, not just what is in the brochure. If you want a quote that lays out every layer, call Sleeping Giant Roofing at (807) 501-9192 or book a free estimate.