Roof and structural assessment

This is the step that most quotes bury and most homeowners discover late. In Ottawa a solar array is not simply screwed to a roof. The City states that the design of solar collector systems and the on-site field review of their installation must be undertaken by a professional engineer licensed in the Province of Ontario (City of Ottawa, Solar collector systems). Getting that done first, and reading what it says, is the cheapest risk reduction available on the whole project.

What the engineer is actually checking. Whether the existing rafters or trusses, and their connections, can carry the additional dead load of panels and racking on top of the snow and wind loads the roof already has to take. Where the racking attachments land relative to structural members. Whether the attachment detail will keep water out for twenty-five years. And, for the permit exemption route, whether the existing roof is in good structural condition. A roof with sagging sheathing, past water damage or undersized members can still take an array, but it needs reinforcement, and that is much cheaper to know before the deposit than after.

Step one: the documents. The engineer wants the roof framing, either from original drawings or from measurements taken in the attic: member size, species and grade if determinable, spacing, span and the truss configuration. For a permit submission the City wants two complete plan sets, roof layouts, cross-sections with dimensions, anchorage details, and confirmation that all existing structural members and connections affected by the installation have been reviewed and that the panels and racking meet the Ontario Building Code.

Step two: the attic and roof inspection. Someone goes into the attic and onto the roof. They are looking for the framing reality rather than the drawing, for water staining that indicates a leak history, for inadequate ventilation, and for the condition of the sheathing. Attic ventilation matters more than people expect: an array shades and slightly insulates the roof deck beneath it, and a poorly ventilated attic with an array over it is a different moisture problem from the same attic without one.

Step three: shingle age, which is a business decision rather than an engineering one. Asphalt shingles in Ottawa's climate typically give fifteen to twenty-five years. A solar array is a twenty-five year asset. If the shingles have more than roughly seven or eight years behind them, reroofing before installation is usually the right call, because removing an array, reroofing and reinstalling it commonly costs $3,000 to $7,000 in labour alone and may not be covered by anybody's warranty. A contractor who does not raise this is either not looking or not telling you.

Step four: shading and orientation modelling. Due south at a tilt somewhere near the latitude is the reference case. East and west elevations produce meaningfully less annually, though a west-facing array shifts its output later into the afternoon, which matters more under some rate structures than others. Shading is assessed with a fisheye-style survey or modelling software rather than by eye, because a chimney or a neighbour's silver maple that looks harmless in April is a different object in September when the sun is lower.

How long it takes. The site visit is usually two to three hours. The stamped report and drawings commonly take one to three weeks depending on the engineer's queue, and that queue is the most common reason a spring installation slips into summer. Book it early.

What it costs in Ottawa in 2026. Indicative. A structural review and stamped letter for a straightforward flush-mounted residential array commonly runs $800 to $2,500. Full design drawings for a building permit submission are usually $1,500 to $4,000. If reinforcement is needed, that is a separate carpentry cost and it varies enormously with access. Some installers fold the engineering into a package price, which is fine as long as you can see what it is and who the engineer is.

What makes an Ottawa roof different. Snow load is the honest centre of it. Panels change how snow behaves on a slope: instead of sliding off progressively, snow can hang up at the array's lower edge, build a drift, and then release as a slab. That matters for what is below, for the gutters, and for ice damming at the eaves. The freeze-thaw cycling here is also hard on roof penetrations, so the flashing detail at each attachment is a durability question rather than a cosmetic one. And much of the city sits on sensitive marine clay that moves seasonally, which shows up in older houses as framing that is no longer quite where the drawings say it is. That is one more argument for measuring rather than assuming.

Who should do the work, and which credential. A professional engineer licensed in Ontario, which you can verify in Professional Engineers Ontario's public directory before you pay anyone. Ask for the engineer's name and licence, not the installer's assurance that an engineer is involved. The field review is a separate deliverable from the design and the City names both, so confirm the fee covers a return visit during installation rather than a drawing alone.

What to ask before you hire. Who is the engineer, by name and licence. Does the fee include the on-site field review as well as the design. Are we taking the permit route or the exemption route, and what does the exemption require in writing. How old are my shingles, and what is your recommendation. Is reinforcement needed, and if so what does it cost. What shading survey method are you using. What annual production figure does the model give, and what snow loss did you assume. Who is liable if the roof leaks at a penetration in year four.