Solar structural review explained

Before a plan reviewer signs off on rooftop solar, someone has to confirm the roof can actually hold it. Structural review is the part of permitting that looks past the wiring and asks a simpler question: will the array stay attached, and will the framing carry the load, for the life of the system? Here's what reviewers check and when an engineer has to be involved.

Dead load: the weight question

A solar array adds distributed dead load to the roof — the modules, the racking, and the fasteners. For a typical residential system this is a modest few pounds per square foot spread across the array area, but the reviewer still verifies it against the roof's structural capacity.

Two things matter here:

• Distributed load across the whole array, which most conventional roofs handle easily
• Point loads at each attachment, where the array's weight and wind forces concentrate on individual rafters or trusses

Older, undersized, or damaged framing can fail the distributed-load check, which is why the reviewer wants to know the existing framing size and spacing.

Attachment: keeping the array on the roof

The bigger structural concern is usually not weight — it's uplift. Wind flowing over a roof creates suction that tries to peel the array off. Reviewers check that attachments resist it by confirming:

• Attachment spacing — how far apart the roof anchors are placed
• Fastener type and embedment — lag screws or structural fasteners landing in the framing, not just the sheathing
• Flashing and load path — each anchor transferring force into a rafter or truss

The racking manufacturer publishes span and spacing tables for given wind and snow conditions. Staying inside those tables is what makes a standard install approvable with prescriptive details.

Wind and snow: the environmental loads

Structural requirements scale with where you build. A reviewer applies your location's:

• Design wind speed, which drives uplift and the required attachment density
• Ground snow load, which adds to the gravity load in cold climates
• Exposure and roof zone, since edges and corners see higher wind forces than the field of the roof

The same array can be prescriptive in a mild climate and require engineering in a high-wind or heavy-snow region.

When a PE stamp is required

Many standard rooftop systems clear structural review using the racking manufacturer's prescriptive details — no engineer needed. But a licensed structural engineer's (PE) stamp is commonly required when:

• The framing is undersized, spaced wide, or altered
• The system is heavy or uses ballasted racking
• It's a ground mount or a non-standard structure
• The install falls outside the racking tables for wind or snow
• The AHJ requires a stamp as local policy

When in doubt, confirm with your AHJ — some jurisdictions require a stamp on every project regardless.

What to have on your drawings

A complete structural submittal shows the existing framing (size, species, spacing), the attachment layout and detail, the racking product and its load tables, and the calculated loads for your site. Missing framing information is one of the most common completeness corrections, alongside the electrical items covered in why solar permits get rejected.

Structural review is a design aid conversation, not a guarantee — a licensed structural engineer must review and stamp anything outside standard prescriptive limits, and your AHJ has the final say on when that's required. Get the framing and attachment details on paper early, and the structural side of your permit clears cleanly.

Educational reference, reviewed 2026-07. A design aid, not a substitute for a licensed electrician or PE. Confirm the enforced NEC edition and local amendments with your AHJ.