Engineer Letter for Permit: What It Is and When You Need One
A sealed engineering letter is often the fastest way to satisfy a building department. Here are the common types, what a good letter contains, and when the department will want full drawings instead.
- An engineer letter is a short, sealed report that states a professional conclusion about a specific structure or condition.
- Common types include structural adequacy, beam and header, solar roof, foundation certification, damage assessment and floodproofing letters.
- A letter works when the question is narrow. New construction or major changes usually need drawings.
- The engineer needs reliable information to sign: photos, measurements, existing plans and sometimes a site visit.
- Ask the building department what the letter must say before you order it.
What an engineer letter is
An engineer letter is a short report, usually one to five pages, signed and sealed by a licensed Professional Engineer. It answers one specific question for a building department, lender, insurer or buyer. For example: is this existing roof strong enough for solar panels, does this beam carry the new load, or was this foundation built to code?
Because it carries the engineer’s seal, the letter is a professional statement of responsibility. That is why building departments accept it in place of more paperwork, and why an engineer will only sign one after reviewing enough information to stand behind the conclusion.
Common types of engineer letters
- Structural adequacy letter. Confirms an existing structure can carry a proposed load, such as rooftop equipment, a hot tub on a deck or new roofing.
- Solar structural letter. Confirms the roof framing and attachments can support a solar array under the site’s wind and snow loads. See solar structural letters.
- Beam and header letter. Sizes or verifies a beam, header or post, often for a wall opening or remodel. See beam and header calculations.
- Foundation certification. Common for manufactured homes, where lenders and departments ask for a PE to certify the foundation and anchoring. See manufactured home foundations.
- Inspection or observation letter. Documents what an engineer observed, for example framing, footings or repairs. See structural inspection letters.
- Damage assessment letter. Evaluates damage after a storm, fire, vehicle impact or settlement and recommends repairs.
- Floodproofing certification. For non-residential buildings in flood zones, a PE certifies that the dry floodproofing design meets the required elevation. FEMA has a standard Floodproofing Certificate for this.
- Letter of certification for a design. Accompanies stamped drawings to certify the design meets code. A recent shipping container building we engineered in New York needed one alongside the structural set.
What a good engineer letter contains
Building departments reject letters that are vague. A letter that gets accepted the first time usually includes:
- Project address and the client
- The purpose of the letter and the question it answers
- What the engineer reviewed: drawings, photos, measurements, site visit, manufacturer data
- Design criteria: code edition, wind speed, snow load, seismic category or soil values used
- Findings and calculations summary
- A clear conclusion, plus any conditions such as required repairs or connectors
- Limitations of the review
- The engineer’s seal, signature and date
If the department gave you a correction notice or checklist, send it with your request. The letter can then answer each item word for word.
Letter or full drawings?
A letter is enough when the question is narrow and the existing condition is known. Drawings are needed when something new is being built or the change affects how loads travel through the building.
- Usually a letter: solar on an existing roof, verifying an existing beam, certifying a manufactured home foundation, documenting a repair.
- Usually drawings: new additions, new foundations, removing a load-bearing wall, new steel framing, decks and patio covers in most jurisdictions.
- Sometimes both: a sealed drawing set plus a letter of certification, which some towns ask for on unusual structures.
On a recent roof addition in Montana, the client needed three existing beams, posts and pier bases verified for snow load. A sealed verification with calculations covered it; no full plan set was required.
What the engineer needs from you
- The project address, so site loads can be looked up
- Photos of the area in question, with a tape measure visible where possible
- Member sizes, spans and spacing
- Any existing drawings, truss layouts or manufacturer documents
- The plan-check comment or the requirement you are trying to satisfy
Some letters, especially inspection and damage letters, require the engineer to see the condition in person. When a site visit is needed, we tell you up front and arrange it through an engineer licensed in your state.
How long it takes and what affects cost
Many letters are completed within a few business days of receiving complete information. Cost depends on how much analysis is required, whether a site visit is needed, and how many elements are being checked. A single beam letter is far simpler than a whole-roof solar evaluation with several framing conditions.
We quote a fixed fee after seeing your information, so the cost is known before work starts. Send the details through the proposal form.
Need a sealed letter for your permit?
Send photos, measurements and the department's request. We reply with a fixed fee and delivery date, usually the same day.
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Frequently asked questions
Is an engineer letter the same as stamped drawings?
No. A letter answers a specific question about a structure or condition. Stamped drawings show how something is to be built. Both carry the engineer’s seal, and some projects need both.
Can an engineer write a letter without visiting the site?
Often, yes, when the condition can be documented with photos, measurements and existing plans. Inspection, observation and damage letters usually need a site visit.
Will my building department accept a letter from an engineer in another state?
Only if the engineer is licensed in the state where the project is located. Every letter we provide is sealed by a PE licensed in your state.
What if the department asks for changes to the letter?
Send us their comments. We revise and reseal the letter to address each item.
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