Insights & Updates

It’s one of the most common questions we hear from homeowners, commercial developers, contractors, and even attorneys: “Do I actually need a structural engineer for this project?”

The short answer: if your project touches a load-bearing element, changes how loads move through a building, involves a permit in most jurisdictions, or could create liability if something goes wrong — yes, you need a licensed structural engineer. A contractor, architect, or handyman cannot legally provide a stamped structural design in most situations.

The longer answer is what this guide is for. Below, we walk through the 10 situations where a structural engineer is required, explain the difference between commercial and residential projects, cover what local building codes typically mandate, and show you what to expect when you hire one.

10 Situations That Require a Structural Engineer

Here are the most common scenarios where a licensed Professional Engineer (PE) is either legally required or strongly recommended:

1. Removing or modifying a load-bearing wall. This is the single most common trigger. Even if the wall “looks” non-structural, an engineer has to verify what’s above it — joists, trusses, roof load — before anything is cut.
2. Adding a second story, dormer, or vertical addition. The existing foundation and framing have to be analyzed to confirm they can carry the new load. This is almost always a PE-required scope.
3. Building a new ground-up structure. Commercial and residential new construction almost universally require stamped structural drawings for the permit.
4. Foundation repair or underpinning. Any work that affects the building’s foundation — helical piers, push piers, crack repair with epoxy injection, wall stabilization — requires engineering oversight.
5. Installing rooftop solar panels. Most jurisdictions now require a structural engineer’s letter (a “PE letter”) confirming the roof can carry the added dead load and wind uplift. (See our PE letter guide for solar installers.)
6. Commercial tenant build-outs that alter structure. Even interior-only tenant improvements can require engineering if they affect load paths, add HVAC equipment, or punch through floors.
7. Post-event damage assessment. After a fire, storm, impact, flood, or earthquake, you need a forensic engineer to evaluate whether the building is safe to occupy.
8. Construction defect or litigation support. Insurance claims, lawsuits, and disputes involving structural issues require a licensed engineer — often as an expert witness.
9. Property condition assessments (PCAs) for commercial real estate. Lenders and buyers routinely require an engineer-signed PCA before closing on a commercial property.
10. Anywhere the building department says so. When in doubt, call your local permitting office. If they ask for “stamped drawings” or “PE calculations,” that’s your cue.

Commercial vs. Residential: Different Requirements

The threshold for when a structural engineer is required differs sharply between commercial and residential projects — and most property owners underestimate this.

Commercial projects almost universally require a PE for anything that touches structure. The International Building Code (IBC), which most U.S. jurisdictions adopt, explicitly calls for “engineered design” on commercial occupancies. If your project requires a commercial permit, budget for structural engineering from the start.

Residential projects fall under the International Residential Code (IRC), which allows prescriptive design (following code tables without engineering calculations) for simple single-family work. But the IRC has strict limits. The moment you exceed those limits — longer spans, heavier loads, irregular geometry, mixed materials, or any “engineered system” — you fall outside prescriptive design and need a PE.

In practice, most residential renovations that involve removing walls, adding stories, or modifying foundations end up requiring an engineer even if the homeowner didn’t expect it.

When Local Building Codes Mandate a PE

Beyond the IBC and IRC, state and local jurisdictions add their own amendments. A few examples from our Southeast markets:

• Georgia amendments to the IBC are enforced at the state level. Atlanta and most metro counties require stamped drawings for any structural modification to a commercial building, and for residential work that exceeds IRC prescriptive limits.
• Florida Building Code (FBC) is among the strictest in the country due to hurricane risk. In the High-Velocity Hurricane Zone (HVHZ — Miami-Dade and Broward counties), almost any structural work requires PE involvement, including simple projects that would not require engineering in other states.
• North Carolina has specific wind load and seismic requirements that often trigger engineered design.
• Tennessee follows the IBC/IRC with state modifications, and cities like Nashville typically require stamped drawings for any structural alteration.

The rule of thumb: if the permit application has a box for “engineer of record” or asks for “stamped drawings,” you need a PE.

The Cost of Skipping a Structural Engineer

We get called in a lot after the fact — after a wall came down that shouldn’t have, after a solar array cracked the roof deck, after a tenant build-out created a sag in the floor above. The cost of fixing a structural mistake is always higher than the cost of engineering it correctly the first time. We’ve seen:

• Failed inspections that shut down a project for weeks
• Permit revocations forcing rework on completed construction
• Insurance denials when damage was traced to unengineered modifications
• Litigation when a defective condition caused injury or property damage
• Full structural rehabilitation projects that only became necessary because an earlier renovation was done without engineering

A structural engineer’s fee on a renovation project is typically 1–5% of construction cost. The fix for an unengineered mistake often runs 20–50%+ of the original project.

What to Expect When You Hire a Structural Engineer

A competent structural engineering engagement usually follows this sequence:

1. Initial consultation. You describe the project, share any drawings or photos, and the engineer identifies scope and licensing requirements.
2. Site visit. The engineer inspects the existing structure — measuring, photographing, and documenting conditions.
3. Analysis. Loads are calculated, existing members are evaluated, and new designs are drafted if needed.
4. Sealed drawings. The final deliverable is a set of drawings and/or calculations stamped with the engineer’s PE seal. This is what the building department will accept.
5. Construction administration. Optional but recommended — the engineer responds to RFIs during construction and performs field observations to confirm work matches the design intent.

Timelines vary. A PE letter for solar can turn around in a few business days. A full commercial structural design may take weeks to months depending on complexity.

How to Choose the Right Structural Engineering Firm

A few things to verify before you hire:

• PE licensure in your state. Engineering is state-licensed. A PE stamp is only valid in the state where the engineer is licensed. For multi-state projects, make sure the firm carries the right licenses — Strut E&I is licensed in 28+ states.
• Relevant specialty. Structural, civil, and mechanical engineering are different disciplines. For building structure work, you want a structural PE.
• Insurance. Professional liability (errors & omissions) insurance should be in place. For significant projects, ask for a certificate.
• Local code experience. Prior work in your jurisdiction means fewer back-and-forth revisions with the building department.
• Communication. Structural engineering involves non-engineers — owners, architects, contractors, lenders, attorneys — all of whom need clear answers. Look for an engineer who explains things plainly.

Frequently Asked Questions

Do I need a structural engineer to remove a wall?
Almost always — even if the wall looks non-structural. Until a PE verifies what’s above the wall (joists, trusses, roof load), you can’t know for sure. A short on-site consultation is usually enough to confirm whether the wall is load-bearing and what’s required to remove it safely.

Do I need a structural engineer for a commercial build-out?
If the build-out alters any structural element, adds equipment loads, or requires a commercial permit, yes. Most commercial tenant improvements involve at least some PE review even if the majority of the work is non-structural.

Do I need a structural engineer for a solar panel installation?
In the large majority of jurisdictions, yes — a PE letter confirming the roof can support the dead load and wind uplift is required for permitting. Ground-mounted solar also typically requires a foundation design signed by a PE.

What’s the difference between a structural engineer and a civil engineer?
Civil engineering is a broad discipline that includes roads, bridges, water systems, grading, and site development. Structural engineering is a sub-specialty focused specifically on buildings and load-bearing systems. Some civil engineers are also licensed structural engineers; most are not. For building structure work, you want a structural PE.

How long does a structural engineering assessment take?
A simple assessment — one wall, one beam, a PE letter for solar — can be turned around in a few business days. Complex projects involving field measurement, load analysis, and sealed drawings typically take two to six weeks depending on scope and how busy the firm is.

Do I need a structural engineer for a permit?
Sometimes. Building departments flag projects that need engineered design either in their submittal checklist or during permit review. If the department asks for “stamped drawings,” “PE calculations,” or an “engineer of record,” you need a structural PE.

Can a contractor do structural work without an engineer?
For prescriptive residential work that falls within IRC tables, yes — contractors can legally frame, build foundations, and install structural components using code-based standard practices. For anything that exceeds prescriptive design, including any engineered system or modification to an existing structure, a licensed engineer’s involvement is required.

Need a licensed structural engineer? Strut Engineering & Investment, Inc. provides PE-stamped structural design, rehabilitation, forensic investigation, solar PV letters, and expert witness services across 28+ states. Contact our team for a consultation on your project.