Obtain Structural Engineering Plans
Structural engineering isn't optional for most additions—it's the document that proves your addition won't collapse, that your foundation will support the load, and that any walls you remove won't bring down the house. Without stamped structural drawings, your permit will be denied.
Quick Summary
Time needed
2-4 weeks
Cost
$1,500 - $5,000
Professional help
Licensed PE required
What a Structural Engineer Does
While your architect designs how things look and flow, the structural engineer ensures everything is safe. They calculate loads, specify materials, and create detailed drawings that tell your contractor exactly what to build.
Why "Stamped" Drawings Matter
A licensed Professional Engineer (PE) literally stamps drawings with their seal, taking personal legal responsibility for the calculations. This stamp is what your building department requires—it's their assurance that a qualified professional has verified safety.
What Engineers Calculate
Foundation Requirements
The engineer determines what type of foundation your addition needs based on:
- • Soil bearing capacity (from soil report)
- • Total building load (dead load + live load)
- • Frost depth in your area
- • Connection to existing foundation
- • Footing size, depth, and reinforcement
Floor and Roof Framing
Every joist, beam, and rafter gets specified:
- • Joist size, spacing, and span (e.g., 2x10 at 16" o.c.)
- • Beam locations and sizes (LVL, steel, glulam)
- • Point load distribution
- • Roof rafter or truss specifications
- • Snow load and wind uplift requirements
Load-Bearing Wall Removal
If you're removing walls to connect spaces, the engineer specifies:
- • Header beam size and material
- • Support posts/columns and their foundations
- • Temporary shoring during construction
- • Connection hardware (hangers, brackets)
Warning: Never remove any wall without engineering analysis. Even "non-load-bearing" walls may carry loads from settling or provide lateral bracing.
Lateral Bracing (Shear Walls)
Your addition must resist horizontal forces from wind and earthquakes:
- • Shear wall locations and specifications
- • Hold-down hardware at corners
- • Sheathing nailing patterns
- • Connection to existing structure
Connection Details
How the addition attaches to your existing home is critical:
- • Wall-to-wall connections
- • Roof-to-wall connections
- • Foundation ties
- • Differential settlement management
What to Expect for Cost
Structural engineering fees vary based on project complexity, your location, and whether you need site visits.
| Project Type | Typical Cost | Timeline |
|---|---|---|
| Simple room addition (single story) | $1,500 - $2,500 | 1-2 weeks |
| Two-story addition | $2,500 - $4,000 | 2-3 weeks |
| Major renovation + addition | $3,500 - $5,000 | 3-4 weeks |
| Complex (steel, cantilevers, etc.) | $5,000 - $10,000+ | 4-6 weeks |
What's Usually Included
- • Initial consultation/review
- • Load calculations
- • Stamped structural drawings
- • One round of revisions
- • Response to plan check comments
What May Cost Extra
- • Site visit to existing structure
- • Additional revision rounds
- • Rush delivery
- • Construction observation visits
- • As-built documentation
Working With Your Engineer
To get accurate, timely structural plans, provide your engineer with:
Required Information
- Architectural plans: Floor plans, elevations, sections
- Soil report: If required by your jurisdiction (usually for large additions)
- Existing framing info: Joist sizes, beam locations if known
- Foundation type: Slab, crawl space, basement, pier
- Project address: For determining code requirements, snow/wind loads
Communication Tips
- • Involve the engineer early—before finalizing architectural plans
- • Ask about potential cost-saving alternatives
- • Discuss if a site visit would be valuable
- • Get a clear scope document before starting
- • Understand what triggers additional charges
How to Find a Structural Engineer
Ask Your Architect
Most architects have working relationships with engineers and can recommend someone they collaborate with regularly. This usually results in smoother coordination between architectural and structural drawings.
Search Professional Directories
The Structural Engineers Association in your state maintains member directories. Look for engineers with residential experience—commercial-focused engineers may be overqualified (and overpriced) for home additions.
Verify Licensing
Confirm the engineer is licensed as a PE (Professional Engineer) in your state. You can verify licenses through your state's professional licensing board website. Out-of-state engineers cannot stamp drawings for your project.
Frequently Asked Questions
Can my architect do the structural engineering?
Only if they're also a licensed structural engineer (rare). Architects can design buildings but cannot stamp structural calculations—that requires a PE license with structural specialization. Some architecture firms have engineers on staff; otherwise, they'll outsource it.
What if the building department asks for changes to the engineering?
This is called "plan check corrections" and is normal. Your engineer should address the comments and resubmit—most include one round of corrections in their fee. Extensive back-and-forth may cost extra.
Do I need structural engineering for a small addition?
It depends on your jurisdiction and what you're building. A simple 12x12 sunroom on slab might not require engineering. A 12x12 bedroom addition with connection to existing structure usually does. Check with your building department before assuming you can skip it.
Will the engineer visit during construction?
Site visits during construction are usually extra and optional for residential projects. However, if you're doing complex structural work (removing load-bearing walls, steel beams), having the engineer verify the work before it's covered provides valuable peace of mind.
Ready for the Next Step?
With your structural engineering plans in hand, you're ready to start understanding the true costs of your addition by calculating cost per square foot based on your specific design decisions.