How to measure a roof in Canada: satellite imagery, feet and squares
A step-by-step way to measure a roof in Canada from satellite imagery, in feet and squares: area, pitch factor, lineal feet, waste and bundles, with a worked example.
To measure a roof in Canada, trace the roof outline on satellite imagery (or your own drone or phone photo), multiply the plan area by the pitch factor, divide by 100 to get squares, then add waste and lineal feet for the edges. The method is the same in Ontario as in Alberta; what changes in Canada is the imagery season, the mix of feet and metres on the paperwork, and the eave protection your province's code asks for.
What you need before you measure a roof in Canada
- A civic address that lands on the right house. Rural routes, concession roads and new subdivisions in the Prairies or the Atlantic provinces are where a pin drops a few lots off. Check the street view or the lot shape before you trace.
- The pitch, or a way to get it. A pitch gauge on site, the plans, or the free pitch finder from the address.
- One unit system for the whole job. For many residential crews in Canada that's feet, squares and lineal feet, with pitch as rise over 12.
Check the imagery for a Canadian winter
Satellite imagery is one day's snapshot. If that day was in January in Winnipeg or Québec City, the roof may be white from eave to ridge: snow hides valleys, softens hips, buries vents and fills low-slope sections, and low winter sun throws shadows that swallow a north-facing rake.
Trace what you can see clearly. Flag what you can't, and confirm it at the walk-around or with your own drone or phone photo once the roof is clear.
Trace the roof and set the pitch
- Trace the outline at the drip edge, overhangs included. You're measuring the roof, not the house footprint.
- Split it into facets at every hip, valley and ridge, and give each facet its own pitch if they differ.
- Label every edge: eave, rake, ridge, hip, valley, step flashing, wall. Edge lengths drive starter, drip edge, ridge cap and eave protection, so an unlabelled edge is a missing line on the order.
- Read the true area: plan area × pitch factor. The factor is a ratio, the same in feet or metres.
| Pitch | Degrees | Pitch factor |
|---|---|---|
| 4/12 | 18.4° | 1.054 |
| 6/12 | 26.6° | 1.118 |
| 8/12 | 33.7° | 1.202 |
| 12/12 | 45° | 1.414 |
For the full table and how to find pitch on site, see how to calculate roof pitch.
Worked example: a Canadian hip-roof bungalow in feet and squares
Take a hip-roof bungalow in Ottawa. Measured at the drip edge, the roof is 48 ft × 30 ft, with an even 6/12 pitch on all four sides.
Area
- Plan area: 48 × 30 = 1,440 ft²
- True area: 1,440 × 1.118 = 1,610 ft²
- Squares: 1,610 ÷ 100 = 16.1 squares
Lineal feet
- Eaves: a hip roof has eaves all the way round, 2 × (48 + 30) = 156 lin ft. That's your starter and eave drip edge, with no rakes.
- Ridge: 48 − 30 = 18 lin ft.
- Hips: each hip covers 15 ft of run in both directions, so its plan length is 15 × 1.414 = 21.2 ft. The rise is 15 × 6/12 = 7.5 ft. True hip length: √(21.2² + 7.5²) = 22.5 ft. Four hips = 90 lin ft.
- Hip and ridge cap: 18 + 90 = 108 lin ft.
Waste and bundles
- Waste: say 12% for a plain hip roof (set your own number by roof type). 1,610 × 1.12 = 1,803 ft², or 18.0 squares.
- Bundles: IKO's Canadian data sheets for laminated lines such as Dynasty and Cambridge list 33.3 ft² per bundle, three bundles per 100 ft². 1,803 ÷ 33.3 = 54.1, so order 55 bundles. Check the wrapper or data sheet for the product you're buying; heavier shakes-look lines cover less per bundle.
Eave protection
- 156 lin ft of eave × one course roughly 3 ft wide = about 470 ft² of membrane for a single course. Whether one course is enough depends on the overhang and on your province's code (next section).
If you want to check the arithmetic, the roof square footage calculator and the shingle calculator run the same steps.
Eave protection and the Canadian code
The National Building Code of Canada (Sentence 9.26.5.1) calls for eave protection on shingle roofs. As the APCHQ guide summarizes it, the membrane runs at least 900 mm (about 3 ft) up the slope from the edge of the roof and at least 300 mm (about 1 ft) past the inner face of the exterior wall. There are exemptions, including unheated garages, carports and porches, eaves where the distance from the roof edge to the inner face of the wall exceeds 900 mm measured along the slope, roofs at 1 in 1.5 (8/12) or steeper, and regions with 3,500 or fewer degree-days.
On a wide overhang, the 300 mm-past-the-wall rule is what forces a second course. Measure the overhang along the slope, not flat.
Provinces adopt their own edition: the Ontario Building Code, the BC Building Code, Alberta's edition, Québec's Code de construction. Check the edition that applies to the job before you order. The ice and water shield calculator does the course count from eave length and overhang.
Where you trip
Measuring the house, not the roof. A footprint from a survey or a tax roll stops at the walls. The roof runs to the drip edge. On a 156 ft perimeter, an 18 in overhang adds about 240 ft² of plan area.
Using plan area for the order. Plan area × pitch factor, every time. At 6/12 the gap is 12%.
Rounding early. Round squares and bundles once, at the end.
Forgetting the edges. Area gets the shingles right; lineal feet get starter, drip edge, cap and membrane right. An unlabelled valley is a missing roll.
Converting twice. Plans in Canada often come in metric. Convert once at the start (1 m² = 10.764 ft², 1 square = 9.290 m²) and don't convert the order back.
How RoofStruct fits a Canadian job
RoofStruct is free, unlimited self-serve measuring and PDF reports, no card. Address search takes Canadian addresses, you trace on satellite imagery or your own drone or phone photo in minutes, and Settings › Localization › Measurement Units switches between Imperial (ft, ft²) and Metric (m, m²) per user, carried into exports. Pitch Notation reads rise over 12, degrees or percent. The app runs in English and Canadian French; the PDF report itself is in English. On Pro, estimates can go out in Canadian dollars, priced per square or per m². If you'd rather not trace it yourself, done-for-you reports exist too.
More on the software side: roof measurement software for Canadian contractors.
FAQ
Do roofers in Canada measure in feet or metres?
Many residential crews in Canada measure in feet and order by the square, because shingles are sold that way. Plans, commercial specs and some permit forms come in metric, so convert once and stay in one system.
How do I turn square feet into squares?
Divide the true area (plan area × pitch factor) by 100. A 1,610 ft² roof is 16.1 squares before waste.
Can I measure a roof from satellite imagery in a Canadian winter?
You can measure what the imagery shows clearly. Snow hides valleys, vents and low-slope sections, so flag those edges and confirm them on site or from your own photo once the roof is clear.
Does eave protection change the measurement?
It changes the order, not the area. Measure the eave length and the overhang along the slope, then apply the edition of the building code your province uses.
Sources
Checked Oct 2026: