Determine Structural Feasibility
For second-story additions, the critical question is: can your existing foundation and walls handle the extra weight? This evaluation should happen before you spend money on detailed architectural plans.
Quick Summary
Structural engineer
$500 - $1,500
Foundation reinforcement
$10,000 - $30,000+
Soil report (if needed)
$1,000 - $3,000
Why Structural Feasibility Matters
Adding a second story essentially doubles the weight on your foundation. Most single-story homes weren't designed for this. If your foundation can't handle the load, you have three options: reinforce it (expensive), build a ground-level addition instead, or don't build at all.
Don't Skip This Step
Building on an inadequate foundation causes settling, cracking, and potentially catastrophic structural failure. This isn't an area to cut corners or guess.
Foundation Types and Their Limits
Poured Concrete Foundation
The strongest foundation type. Most can handle a second story if walls are 8+ inches thick and footings are adequate. Built since 1950s in most areas.
Typical reinforcement cost: $5,000 - $15,000 (if needed)
Concrete Block Foundation (CMU)
Common in older homes. Strength depends on whether cells are filled with concrete/rebar. Unfilled block walls typically need reinforcement.
Typical reinforcement cost: $10,000 - $25,000
Stone/Brick Foundation
Found in pre-1940 homes. Often lacks steel reinforcement and may have deteriorated mortar. Usually requires significant reinforcement or underpinning.
Typical reinforcement cost: $15,000 - $40,000+
Crawl Space on Piers
Pier foundations support the house at points rather than along perimeter. Often inadequate for second story without major reinforcement or replacement.
Typical reinforcement cost: $20,000 - $50,000+
Slab-on-Grade
No basement or crawl space. Capacity depends on slab thickness, reinforcement, and soil conditions. Post-tension slabs are usually stronger than conventional.
Typical reinforcement cost: $10,000 - $30,000 (if needed)
Warning Signs to Look For
Before hiring an engineer, look for these signs that may indicate existing foundation problems (these need to be addressed regardless of addition):
Interior Signs
- • Diagonal cracks from door/window corners
- • Doors that stick or won't latch
- • Windows that won't open or close easily
- • Sloping or uneven floors
- • Gaps between walls and ceiling/floor
Exterior Signs
- • Horizontal cracks in foundation
- • Stair-step cracks in block foundations
- • Bowing or leaning walls
- • Gaps around exterior doors
- • Chimney pulling away from house
Note: Small hairline cracks are normal (concrete cures and settles). Wide cracks (1/4" or more), horizontal cracks, or cracks that grow over time indicate problems that need professional evaluation.
Hiring a Structural Engineer
A licensed structural engineer is essential for second-story additions. They'll evaluate your existing structure and design reinforcement if needed.
What They'll Evaluate
- Foundation type and condition - Can it support additional load?
- Existing wall framing - Can walls transfer loads to foundation?
- Load paths - How does weight travel through the structure?
- Soil conditions - May recommend geotechnical report
Feasibility Assessment
Initial evaluation to determine if project is possible
$500 - $1,500
Full Structural Plans
Detailed engineering drawings for permit
$2,000 - $6,000
Finding an engineer: Ask your architect for recommendations, or search your state's professional engineering board for licensed structural engineers (SE or PE).
Soil Conditions Matter
Even a good foundation can fail if soil conditions are poor. These issues affect both second-story and ground-level additions:
Expansive Clay Soil
Swells when wet, shrinks when dry. Common in Texas, Colorado, and parts of California. May require special foundation design or soil treatment.
High Water Table
Groundwater close to surface can undermine foundations. May need drainage systems or specialized foundation types.
Fill Soil
If your lot was filled before building, that soil may not be compacted well. Can settle over time. Common in hillside developments.
Your structural engineer will recommend a geotechnical report ($1,000-3,000) if soil conditions are a concern.
Frequently Asked Questions
If my foundation needs work, should I just do a ground-level addition instead?
It depends on costs and your lot. If reinforcement costs $25,000+ and you have space, a ground-level addition may be more cost-effective. If you're tight on lot coverage, reinforcement may be your only option. Compare total costs.
Do ground-level additions need structural engineering?
Usually less intensive, but still needed. The engineer will design the new foundation and verify the tie-in to existing structure. Permits require stamped structural drawings for almost all additions.
How long does structural evaluation take?
Initial site visit: 1-2 hours. Report delivery: 1-2 weeks. Full structural plans (if you proceed): 2-4 weeks. Plan this into your timeline before starting architectural design.
Ready for the Next Step?
With feasibility confirmed, it's time to move into the design phase and hire an architect or designer to create detailed plans.