Do I need a structural letter for solar panels?

The review needs more than a panel count. I look for the module and rail layout, attachment spacing, ballast weights, inverter and equipment locations, roof zones, existing framing, roof age or condition, and proposed installation method so the responsible engineer can identify the loads and connections that require review.

• Current roof plan, framing plan, and equipment layout
• Panel, rail, attachment, ballast, and manufacturer data
• Roof sheathing, joists or rafters, beams, trusses, and support lines
• Existing rooftop equipment, penetrations, repairs, and access conditions

Solar arrays can add dead load and create uplift, sliding, attachment, concentrated, maintenance, or equipment forces. The engineer traces those forces through fasteners or ballast, roof sheathing and framing, connections, and foundations or other supports while accounting for the actual roof geometry and design criteria.

• Dead load, uplift, lateral, seismic, and attachment forces as applicable
• Local sheathing and member capacity at attachment points
• Load distribution, transfers, blocking, and connection details
• Roof condition and water-intrusion risks outside the structural calculation

A letter should distinguish observation from analysis, identify records relied upon, state exclusions, and avoid conclusions broader than the reviewed system. Electrical interconnection, fire, roofing, utility, and authority requirements may need separate review; the letter cannot promise an agency decision.

• Date, address, system description, and documents reviewed
• Analysis methods, assumptions, field observations, and unresolved limitations
• Defined conclusion tied to the reviewed array and supporting structure
• Separate responsibility for electrical, roofing, fire, utility, and permit decisions