Document review, no site visit
Solar Structural Letters in Texas, Sealed by a Licensed PE
The stamped letter your plan reviewer asks for before a rooftop array goes on: existing framing capacity, wind uplift at the actual site, and attachment spacing that resists it.
Opening soon
Sealed Engineering is not yet accepting orders. Firm registration is pending with the Texas Board of Professional Engineers and Land Surveyors, and no engineering services are being offered or performed under this brand until it is granted. Founding customers on the waitlist are contacted first when ordering opens.
What a solar structural letter actually says
A solar structural letter is a short engineering opinion, sealed and signed, addressed to the authority having jurisdiction. It answers three questions and stops there.
First, whether the existing roof framing can carry the array. A residential PV array adds roughly three to five pounds per square foot of dead load, distributed through the standoffs into the rafters or truss top chords. That is a modest number, which is exactly why the answer is usually yes, and exactly why the letter still has to be written by somebody who checked rather than assumed. A 2x4 truss at 24 inches on center spanning 24 feet with an existing tile roof is a different conversation than a 2x6 rafter at 16 inches under composition shingle.
Second, whether the attachments resist wind uplift at that specific address. Uplift is where roof mounted PV is actually governed, and it is not a national number. ASCE 7 assigns a basic wind speed by location, and Texas spans a very wide range of them. An array in Amarillo and the same array in Corpus Christi are two different uplift problems with two different attachment spacings.
Third, whether the specific attachment being used develops the capacity the calculation demands. Lag screw diameter, embedment depth into the framing member, the species and grade of that member, and the spacing along and across the array all appear in the check. This is the part that most often changes a design: the framing passes and the attachment spacing has to tighten.
Why Texas is not one wind zone
Texas is the reason a national template letter is a liability. The basic wind speed under ASCE 7 for a Risk Category II residence runs from the low hundreds across most of the interior up past 140 miles per hour on the coast, and the exposure category shifts it again depending on whether the house sits inside a suburban tract or alone on open ranch land.
The fourteen seaward counties and part of Harris County carry a second layer on top of that, the Texas Department of Insurance windstorm requirements, which is a separate certification path and not something a structural letter satisfies on its own. If the array is going on a roof in that region, the windstorm question needs answering alongside the structural one.
- Panhandle and West Texas: high basic wind speed, frequently open exposure, and the attachment spacing tightens for it.
- Central and North Texas: moderate wind, but older housing stock with cut or modified framing that has to be looked at rather than assumed.
- Coastal counties: highest wind speeds in the state plus a separate TDI windstorm certification path.
When the answer is not a clean yes
Sometimes the framing does not carry the array as designed. That is a real outcome and it is not a failed order. What comes back in that case is the reason and the remedy: sister the rafters over a defined span, reduce the array footprint on the affected plane, move to a different attachment with greater withdrawal capacity, or tighten spacing.
An engineer seals what the evidence supports. That is the entire value of the seal, and it is why nobody here will tell you in advance what the letter will conclude.
What arrives
- A sealed and signed letter on engineering letterhead, dated, addressed to the permit office.
- The governing code edition and the ASCE 7 basic wind speed used for the site address.
- The framing members reviewed, with span, spacing, species, and grade as provided.
- Attachment type, fastener size, embedment, and the maximum spacing the calculation supports.
- Any conditions or reinforcement the conclusion depends on, stated plainly.
- Digital PDF with the seal applied, suitable for direct upload to the permit portal.
Built as a document review, so nothing waits on a site visit or a homeowner's schedule.
What has to exist first
An engineer seals what the evidence supports, so this list is the work rather than the paperwork around it. Anything missing is named rather than assumed.
- Site address, so the wind speed and exposure are the real ones.
- Roof framing information: member size, spacing, span, and species or grade if known.
- Photos of the attic or framing, including any cut, notched, or modified members.
- Array layout drawing showing module positions on each roof plane.
- Module and racking cut sheets, including the attachment or standoff being used.
- Roof covering type and approximate age.
Solar Structural Letters: common questions
Does every solar permit in Texas need a structural letter?
No. It depends entirely on the authority having jurisdiction. Some Texas cities accept a manufacturer's certification for standard framing, some require a sealed letter on every rooftop array, and some only ask when the framing is trusses of unknown origin or the roof covering is tile. Check the plan review checklist for the specific city or county before ordering.
Do you need to visit the roof?
No. A solar structural letter is written from documents: the framing information, attic photos, the array layout, and the equipment cut sheets. That is why it is the fastest deliverable in the catalog. If the framing cannot be established from what is submitted, the letter cannot be sealed on assumption, and the missing item is named rather than guessed.
What if the array is on a tile or metal roof?
Both are handled, and both change the analysis. Tile adds significant existing dead load, which is the case where framing capacity is genuinely in question rather than a formality. Metal roofs usually move the question from lag screws into clamp or seam attachment, where the capacity comes from the manufacturer's tested values rather than from wood withdrawal.
Can one letter cover a whole batch of installs?
Not as a single document. Each address has its own wind speed, exposure, framing, and array layout, and a letter that covered several would be sealing an opinion about houses nobody examined. Volume is handled by making each letter fast and the intake repeatable, not by generalizing the seal.
Is a structural letter the same as a windstorm certificate?
No. A structural letter addresses whether the roof framing and attachments handle the array. A WPI-8 windstorm certificate is a Texas Department of Insurance compliance document for construction in the fourteen seaward counties and part of Harris County, and it is required for windstorm insurance eligibility rather than for structural permitting. A coastal solar project often needs both.
Where this is ordered most in Texas
Wind speed, soil, and the permit office all change by market, and so does what this document has to address. These pages are written for the market rather than templated across it.
Often needed alongside this
- Documents or site visitStructural Letters for PermitsPlan review asked for a sealed letter and the project stopped. This is the deliverable that restarts it: a specific structural question answered, sealed, and addressed to the reviewer who asked.What it contains
- Site visit requiredWPI-8 Windstorm CertificationsThe Texas Department of Insurance certificate of compliance that windstorm coverage depends on, obtained through the licensed engineer path rather than the TDI inspector queue.What it contains
- Documents or site visitBeam and Header Sizing LettersTaking a wall out, or opening one up. The beam gets sized against the real loads, the bearing gets checked, and the load path gets followed all the way down instead of stopping at the ceiling.What it contains
Need a solar structural letter?
Start with the property address and we will tell you exactly what else is needed.
Opening soon. Founding customers get first turnaround slots.