ROOFING101.
What's actually up there, how long it lasts, and when it's done.
- GUIDES
- 4
- GLOSSARY TERMS
- 27
A roof isn't the shingles. The shingles are the part you see, and they're the last line of a system that runs from the decking nailed to your rafters, through the underlayment and flashing, to the vents that let your attic breathe. Most roof failures start in the parts you can't see.
Calgary is harder on that system than most of North America. Hail, chinook freeze-thaw swings, UV at altitude and heavy wet spring snow all work on it at once. Start here if you want to understand what you own before anyone quotes you on it.
- What are the layers of a roof and what does each one do?
- How long should my roof last in Calgary?
- Should I repair it or replace it?
- How is a flat roof different from a sloped one?
READ THEM IN THIS ORDER.
- 01How a roof works, layer by layerA sloped roof is a stack of layers, each with one job: the wood deck carries the load and holds the nails, underlayment and ice and water shield back up the shingles, flashing seals the joints, the shingles shed water, and vents keep air moving underneath. Most leaks start at the joints and edges, not in the open field of shingles.
- 02How long does a roof last in Calgary?By published estimates an asphalt shingle roof lasts roughly 20 to 30 years and metal 40 or more. In Calgary, hail, strong sun, chinook temperature swings and attic ventilation decide how much of that you actually get, and one bad hailstorm can end a roof at any age.
- 03Repair or replace your roof? A decision frameworkRepair the roof if the problem is in one place and the rest is healthy; replace it if the same failure shows up across several slopes, the shingles are brittle, the deck is damaged, or there are already two layers. If hail caused it, it's an insurance question first, because shingle warranties exclude hail.
THE BASICS
Plain-language primers. Assume nothing.
How a roof works, layer by layer
A sloped roof is a stack of layers, each with one job: the wood deck carries the load and holds the nails, underlayment and ice and water shield back up the shingles, flashing seals the joints, the shingles shed water, and vents keep air moving underneath. Most leaks start at the joints and edges, not in the open field of shingles.
How long does a roof last in Calgary?
By published estimates an asphalt shingle roof lasts roughly 20 to 30 years and metal 40 or more. In Calgary, hail, strong sun, chinook temperature swings and attic ventilation decide how much of that you actually get, and one bad hailstorm can end a roof at any age.
Flat and low-slope roofs, explained
A flat or low-slope roof (anything under a 3-in-12 pitch) can't rely on shingles. It needs a continuous waterproof membrane with sealed seams, such as TPO, EPDM or modified bitumen, and drainage that clears standing water within 48 hours; seams, drains and flashing are the weak points, so check them every spring and fall.
DEEP DIVES
For when you're mid-decision, mid-claim or mid-argument.
THE ROOFING 101 GLOSSARY.
- Attic
- The space between the top-floor ceiling and the underside of the roof. In most houses it's meant to stay cold and ventilated in winter, close to the outdoor temperature.
- Built-up roofing
- A flat-roof system made of alternating layers of asphalt and reinforcing felts built up on the roof, often surfaced with gravel. Often shortened to BUR.
- Cricket
- A small raised ridge built on a roof to divert water around a chimney, rooftop equipment or another obstacle.
- Decking
- Another name for the roof deck, the panels or boards the roofing is nailed to. Damaged decking is usually found only after tear-off.
- Discontinued shingle
- A shingle line or colour the manufacturer no longer makes. It can be hard to match in a repair, and shingle warranties commonly exclude colour or shade variation.
- Eave
- The lower edge of a roof that overhangs the wall. It's where water leaves the roof, the eavestrough hangs and ice dams tend to form.
- EPDM
- Ethylene propylene diene monomer, a synthetic rubber single-ply membrane for flat and low-slope roofs.
- Hip
- The sloped ridge where two roof planes meet at an outside corner, running from the ridge down to the eaves. Like edges and ridges, hips are more exposed to wind lifting shingles.
- Limited lifetime warranty
- A manufacturer warranty that covers manufacturing defects, with full coverage for an initial period and prorated coverage after that. It isn't a guarantee of how long the roof will last, and it excludes weather like hail.
- Low-slope roof
- A roof with very little pitch. Shingle makers set a minimum slope and extra underlayment rules for these roofs, and flatter roofs need membrane roofing instead of shingles.
- Modified bitumen
- A flat-roof membrane of asphalt modified with SBS or APP polymers, supplied in rolls and built up in layers.
- OSB
- Oriented strand board, the chip-looking panels of wood strands pressed with resin that are often used for roof decking. Wet OSB swells and softens, and nails stop gripping it.
