Is your roof ready for solar panels?

How old can the roof be?

Panels are meant to stay up for a couple of decades or more, so the roof beneath them should have at least that much life left. Taking an array off to re-roof means paying twice for labour: once to remove and refit the panels, again for the roofers. Asphalt shingles, metal, tile and membrane roofs all age at different rates, and your roofer or inspector can estimate what remains on yours.

If the roof is near the end of its life, replace it first or time the two jobs together. Some installers coordinate with a roofing contractor so the new surface and the racking go on in one project. Ask the installer to confirm in writing who is responsible if the roof leaks at a mounting point, a topic covered in roof leaks and flashing around solar panels.

Is the roof structure strong enough?

Modern panels and racking add a modest load per square metre, but roofs in Canada also carry snow, and the design snow load varies a lot between regions. The rafters or trusses, the sheathing and the attachment points all need to be sound. Rot, sagging, or past damage will show up at the survey.

Older homes and roofs altered by renovations are the ones most likely to need a structural opinion. Where there is any doubt, the installer or a structural engineer can review the framing before anything is bolted down. Local building rules decide when that review is required, so ask your municipality or the installer about the permit process. The Alberta permit guide gives an example of how that works in one province.

Which roof direction and tilt work best?

In Canada a south-facing roof gets the most yearly energy, while east and west faces still produce well and often fit household use patterns better. North-facing slopes are usually poor candidates. Tilt matters less than people expect: a typical roof pitch is close enough to the ideal that the gain from changing it is small. A full comparison is in the best solar panel direction in Canada.

Flat roofs are a separate case. Racking can set the panels at a chosen angle, held down by weight or by fixings through the membrane, and the roof still needs to bear that load. How much sun your location gets through the year is explained in peak sun hours across Canada.

How much shade and space do you need?

Trees, chimneys, dormers and neighbouring buildings cast shade that moves across the roof through the day and the seasons. Even a small shadow on one panel can reduce output from a whole string unless the design uses panel-level electronics. A good survey checks shade at several times of year, not just on the day of the visit.

Space is the other limit. Panels are roughly two square metres each, and codes normally require clear pathways, setbacks from edges and access for firefighters and maintenance. The usable area is therefore smaller than the full roof. To see how many panels a home may need, read how many solar panels power a house, and use the installer checklist to confirm the quote reflects a real survey.

What else should you check before booking a survey?

Think about snow behaviour: snow can slide off smooth panels in a rush, so entrances and walkways below the array deserve attention, and the snow removal guide covers safe habits. Check your home insurance conditions, as set out in insurance after a solar install. If a ground-mounted array would suit your property better than a weak roof, that is an option worth pricing.

Finally, take photos of the roof, the attic or framing and the electrical panel. They help an installer give a more accurate first quote.

Quick answers