Engineer Letter vs. Sealed Drawings — Which Does Your Permit Need?

A building department plan-review comment comes back: “Submit engineer-sealed documentation.” The question becomes — is that a letter, a set of drawings, or both? The answer depends on the phase of the project and what the jurisdiction is actually asking to review.

Engineer letter: retrospective certification

An engineer letter is generally issued after the work is in place. It documents the engineer’s professional opinion, based on inspection and available records, that the existing work meets the applicable code. Typical uses:

• Missed-inspection closeouts (see our guide).
• Foundation certifications for home sales or loan closings (see the Texas foundation article).
• Manufactured home to real property conversions (see the mobile home article).
• Post-storm repair permit closeouts (see the storm closeout article).
• Structural opinion letters requested by lenders, buyers, or insurers.

The letter is a narrative deliverable with photographs, references to the applicable code, and a sealed professional opinion. It is typically 2–10 pages.

Sealed drawings: prospective design

Engineer-sealed drawings are issued before construction. They are the design itself — framing plans, foundation details, connection schedules, load calculations attached as an appendix. They are what the contractor builds from and what the inspector inspects against. Typical uses:

• New construction of anything beyond the IRC prescriptive path.
• Additions, second-story conversions, and major renovations.
• Commercial, multi-family, and any structure outside IRC scope.
• Projects in seismic or high-wind zones that exceed prescriptive limits.
• Foundation designs on expansive soil, fill, or high-water-table conditions.

Sealed drawings are a design deliverable: floor plan, foundation plan, framing plan, details, calculations. They can run from a few pages to dozens depending on scope.

When both are needed

The most common crossover scenario: a project was built without engineering, the inspector has flagged structural concerns, and the path to approval is (a) retroactive drawings documenting the as-built and (b) a letter certifying that the as-built matches the drawings and meets code. We see this mostly with owner-built structures, contractor-built projects that skipped engineering to save a few hundred dollars, and inherited situations where the prior owner never completed the paperwork.

What we charge and how fast

Letters: typically flat-rate by letter type, issued in 24–48 hours from the site visit.

Drawings: hourly or by-project, typically 1–3 weeks depending on complexity.

Package (drawings + letter): scoped together, usually at a discount vs. booking separately.

If you are staring at a plan-review comment and not sure whether you need a letter or drawings, email our intake team with the comment and a few photos. We will tell you which one fits and quote it on the spot.