Start before the truck rolls
Most commercial rooftop surveys that go wrong were already going wrong the day before. The crew arrives without the roof warranty, without the single-line diagram, and without the name of the person who holds the roof hatch key. A checklist that begins on the roof is a checklist that starts too late.
Ask the building owner or facility manager for a small, specific package: existing architectural and structural drawings or as-builts, the roofing warranty and the contact for the roofing contractor, the electrical single-line diagram if one exists, twelve months of utility bills, and any tenant restrictions on access hours. Confirm roof access in writing, including who escorts the crew and whether any area is off limits. Our overview of commercial survey requirements explains why each of these documents matters to the engineer who receives the survey.
Roof surface: what the array will sit on
- Roof type and membrane. TPO, PVC, EPDM, modified bitumen, built-up, or metal. Photograph a clear section of the field and a seam or lap so the engineer can identify the system.
- Condition. Ponding, blisters, open seams, patches, soft spots and failed flashing, each located on a roof sketch rather than only photographed.
- Drainage. Drains, scuppers, overflow outlets and the slope direction between them. Array rows and ballast cannot be allowed to dam water.
- Penetrations and curbs. Vents, pipes, hatches, skylights, exhaust fans and curbs, positioned with dimensions from a fixed reference such as a parapet corner.
- Rooftop equipment. HVAC units, ductwork, gas lines, antennas and satellite dishes, plus the service clearance each unit needs around it.
- Parapets and edges. Height on every side, material, and whether there is existing guardrail or an anchor system.
Roof structure: the part imagery cannot see
The structure under a commercial roof is where late surprises live. The checklist should force a measured record rather than a guess. Record the framing type (open-web steel joists, joist girders, wood trusses, glulam, or precast concrete), the joist or truss depth, the spacing center to center, the clear span between supports, and the deck type and gauge. Photograph any stamped or painted joist designation that is still legible, because it lets the engineer look up capacity.
Note where the column lines and heavier girders run. Equipment and ballast concentrations belong near them. Where drawings exist, verify them against what you can see; decades of re-roofing, added rooftop units and tenant changes mean the drawings and the building drift apart. Flag every discrepancy instead of quietly choosing one. The detailed method is covered in our note on roof structural assessment for commercial solar.
Electrical room: where system size is often decided
Walk from the utility meter inward. Photograph the meter and the current transformer cabinet, the service entrance, the main switchboard or switchgear nameplate, the main device, the bus rating and any available fault current label. Capture the service voltage and configuration, the transformer nameplate and owner, and the wall and floor space available for inverters, combiners and disconnects with the working clearances required in front of electrical equipment.
Photograph both potential interconnection approaches, a load-side breaker connection and a supply-side tap, even if one looks obviously better. The engineer decides, and cannot decide from photographs that were never taken. A dedicated note covers the details of electrical service and interconnection survey items, and another covers main switchgear photos and documentation.
Site logistics: access, staging and safety
- Roof access method: interior ladder, hatch, exterior ladder or lift, and who controls it.
- Fire access: roof pathways required by the adopted fire code, hydrants, fire lanes and where they meet the roof access point.
- Crane or lift location, reach to the roof, overhead lines and ground bearing for outriggers.
- Equipment staging areas that do not block tenants, loading docks or truck turning.
- Tenant and operations constraints: shutdown windows for the tie-in, noise limits and escort rules.
- Fall protection: parapet height, guardrails, anchors and skylight screens, so the install crew can plan protection before mobilizing.
Close the visit with a review
Before the crew leaves the roof, someone other than the person who took the photographs should walk the checklist against the captured set. Are the roof dimensions complete? Is every nameplate legible, not just present? Is there a photo of each obstruction and a position for it? Reviewing on site costs minutes. Discovering the same gaps from the office costs a return visit, and on a commercial site that can mean rebooking a lift and an escort.
The best checklists also separate measured facts from assumptions. If the joist depth could not be measured because a ceiling blocked access, the record should say so plainly instead of leaving a blank the engineer might misread as zero concern.
What a finished record looks like
A finished commercial rooftop record gives the engineer a dimensioned roof plan with obstructions, drains and parapets; framing and deck data; legible electrical nameplates; both interconnection options photographed; the proposed equipment location and conduit route; and the access, crane and safety notes. Solar Survey AI performs this as a commercial on-site survey covering roof, structure and electrical room in one visit, with the deliverable 48 hours after the survey. The same record feeds C&I design and engineering, which is PE stamped, so nothing has to be re-measured between survey and plan set.
For a broader residential counterpart, see the site survey checklist built backwards from rework. The commercial version differs mainly in how many parties read the result and how expensive a missing measurement becomes.