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Solar Structural Letters for Texas Installations
The sealed structural review most Texas jurisdictions require before a rooftop solar permit is issued: framing capacity, attachment detail, and wind loading for the site.
What it is
Solar Letters, in plain terms
The sealed structural review most Texas jurisdictions require before a rooftop solar permit is issued: framing capacity, attachment detail, and wind loading for the site.
A solar structural letter is the sealed engineering review a building official asks for before permitting a rooftop photovoltaic array. It answers one question in writing: can this roof structure carry this array, attached this way, under the loads that apply at this address.
The review takes the existing framing as it is. Rafter or truss size, spacing, span, and species, along with the condition of the members, are recorded from the field, together with the array layout, the racking system, the attachment type, and the spacing of the standoffs. Dead load from the array is combined with the wind loading derived for the site under ASCE 7 and the applicable edition of the International Residential Code or International Building Code.
Texas wind speeds are not uniform, and neither are the exposure categories. A design wind speed near the coast, on the Panhandle plains, and in a sheltered suburban infill lot inside Loop 410 produce three different answers for the same array, which is why the letter is written for an address rather than for a product.
Who orders one
The people who need this document
- Solar installers and EPCs assembling a permit package
- Homeowners whose jurisdiction has returned a permit application asking for an engineer's letter
- Commercial owners adding a ballasted or attached array to an existing roof
- Racking and equipment suppliers supporting a dealer network across multiple jurisdictions
The deliverable
What arrives at the end
- A signed and sealed letter stating the framing as found, the array and attachment reviewed, the loads applied, the code edition used, and the structural conclusion.
- Where reinforcement is required, the detail that makes the installation work, rather than a refusal with no path forward.
- A PDF formatted for submission to the authority having jurisdiction, with the address, the scope, and the seal where a plans examiner expects to find them.
What an order asks for
Worth having to hand. Nothing here is unusual, and an order that arrives with it moves without anybody having to telephone back.
- Why do you need this
- What kind of property
- The array layout
- The mounting and attachment details
Where it matters most
Regions where this work carries the most weight
Coverage is statewide. These are the regions whose conditions put this service near the front, and why.
Questions
Common questions
- Does every Texas jurisdiction require a structural letter for solar?
- No, and it is worth checking before ordering one. Requirements vary by authority having jurisdiction and by the size and attachment method of the array. Many cities require a sealed letter for any rooftop array, some require one only above a threshold, and some accept a manufacturer's certification for a listed racking system.
- What information does an engineer need from the installer?
- The address, the array layout and module count, the module weight, the racking system and attachment hardware, the standoff spacing, and framing measurements taken on site: member size, spacing, span, and species where it can be determined. Photographs of the attic framing are worth more than a description of it.
- What happens if the existing framing will not carry the array?
- The letter says so, and where it can be solved it states what would solve it. Sistered members, blocking, or a revised standoff layout resolve most residential cases. A letter that simply declines and stops is a letter the installer cannot use.
- Is a ground mount treated the same way?
- No. A ground mount is a foundation and a frame rather than a review of existing roof framing, so it is a design task with its own soil and wind considerations. It is a different scope with a different deliverable.
Start a job
Tell us what the letter is for and we will tell you yes or no
Send the address, what the document is for, and the date it has to be in hand. Some jobs this firm cannot take, and you will hear that in the first conversation rather than after you have paid and waited.