Buildings & Structural

Structural Letter for Rooftop Solar

A stamped engineer letter confirming your roof framing can carry solar panels, required by many permit offices and installers. Typical US fees run $150 to $800, and most projects take 2 days to 2 weeks. Our drawings, calculations and reports are sealed by a Professional Engineer (PE) licensed in the state where your project is located, ready for permit submission.

Typical US fee$150 to $800

Typical timeline2 days to 2 weeks

Permit drawingsSealed by a PE

What the work involves

Many building departments require a structural letter or calculations showing the roof can carry the added dead load and wind uplift of a solar array. The engineer reviews rafter size, spacing, span and condition, and the racking attachment layout, then issues a stamped letter or specifies reinforcement such as sistered rafters. Installers often order these in bulk, but homeowners sometimes need one directly for a DIY or older-roof installation.

When you need it

Permit office requires a stamped solar structural letter
Older home or unusual roof framing
Heavy snow or high wind region
Ground-mounted array that needs footing design
Installer flags rafters as undersized

What you receive

Stamped structural letter
Attachment and uplift calculations
Rafter reinforcement detail if needed
Ground mount footing design

What drives the cost

Estimate. Fixr lists simple structural letters at $100 to $200 and HomeAdvisor general structural reports at $350 to $800; solar letters fall in this range, with ground mounts or reinforcement costing more.

Related calculators

Roof Pitch CalculatorConvert roof pitch (rise per 12 in of run) to angle and percent, and calculate rafter length and the pitch multiplier.Flat Roof Snow Load Calculator (ASCE 7)Calculate the ASCE 7 flat roof snow load pf = 0.7·Ce·Ct·Is·pg and the minimum roof snow load from ground snow load.Wind Velocity Pressure Calculator (ASCE 7)Calculate ASCE 7 velocity pressure qz from basic wind speed and exposure factors, with a simple windward wall pressure estimate.

Frequently asked questions

How much does structural Letter for Rooftop Solar cost?

Across the US, structural Letter for Rooftop Solar usually costs $150 to $800. Estimate. Fixr lists simple structural letters at $100 to $200 and HomeAdvisor general structural reports at $350 to $800; solar letters fall in this range, with ground mounts or reinforcement costing more.

How long does structural Letter for Rooftop Solar take?

Plan on 2 days to 2 weeks from signed proposal to stamped deliverables, longer if a site visit, soil testing or a permit review cycle is involved.

Do I need a licensed PE for structural Letter for Rooftop Solar?

In most US jurisdictions, yes. When the work needs a permit, the plans, calculations or report usually must be sealed by a Professional Engineer licensed in the state where the project is located. Every deliverable we issue for permit is sealed that way.

Will I also need a structural engineer?

Sometimes. Depending on the site, structural Letter for Rooftop Solar can also involve a structural engineer, solar installer or electrician. We tell you up front which other professionals your project needs and coordinate with them so the drawings agree.

Who do you provide structural Letter for Rooftop Solar for?

Most of our clients for this service are homeowners and contractors. Describe your project and one of our engineers will reply with scope, fee and schedule.

Why does my solar permit need an engineer?

Panels add weight and create wind uplift on the roof. Jurisdictions want confirmation that the framing and attachments can resist those loads.

Can the engineer do it remotely?

Many letters are prepared from installer photos and attic measurements. Older or damaged framing may require a site visit.

What if my rafters are too small?

The engineer can specify reinforcement such as sistering rafters or adding supports, or recommend a different attachment layout. Reinforcement is usually modest work done from the attic before panels go on.

Is the electrical design included?

No. Electrical design is handled by the installer or an electrical engineer, separate from the structural letter.