Cost to Second Story Addition in St. Louis, MO (2026)
If you’re budgeting a second story addition in St. Louis, most projects run $100,931-$302,793, 1% above the $175,000 national average. What moves that number most is usually one thing: Foundation and First-Floor Capacity. On its own it can swing the cost by $10,000 - $60,000, so that’s the decision to slow down on before you sweat the smaller stuff.
Easiest place to save: Commission a structural engineering report ($500-$1,500) before finalizing your budget. Foundation issues discovered mid-project are far more expensive than catching them upfront.
$100,931-$302,793 in St. Louis
1% above the national average · 1.01x cost multiplier
In St. Louis, a second story addition runs $100,931 to $302,793 on average - about 1% above what homeowners pay nationwide. The Midwest market's labor costs account for most of the gap, with material pricing and local permitting fees adding to the spread. Use the cost table below to compare budget, mid-range, and premium options side by side.
Cost Breakdown in St. Louis
| Line Item | Low | Mid | High |
|---|---|---|---|
| Cost per sq ft | $151 | $252 | $404 |
| Materials | $37,600 | $70,500 | $131,600 |
| Labor | $54,548 | $92,732 | $152,735 |
| Permits | $4,700 | $7,520 | $11,280 |
| Design | $6,580 | $11,280 | $23,500 |
| Total | $103,428+1% vs. national avg | $182,032+1% vs. national avg | $319,115+1% vs. national avg |
Budget
Full second story over a 1,000 sq ft footprint with standard materials, vinyl siding, builder-grade windows, and basic finishes. Minimal interior customization.
Mid-Range
1,200 sq ft second story with mid-grade finishes, fiber cement siding, energy-efficient windows, 3 bedrooms, 2 bathrooms, and dedicated HVAC system.
Premium
1,500+ sq ft second floor with custom architectural design, premium finishes, vaulted ceilings, master suite with luxury bath, and full structural engineering.
Material Options
Material prices below are national averages; availability in St. Louis may shift costs slightly.
| Material | Cost/Unit | Best For |
|---|---|---|
| Wood Frame with Vinyl Siding | $150-$200 per sq ft | Budget-conscious projects on homes that already have vinyl sidingMost affordable construction method, fast framing, widely available contractors |
| Wood Frame with Fiber Cement Siding | $200-$280 per sq ft | Mid-range additions where exterior quality and longevity matterDurable, paintable, low maintenance, matches most existing home styles, fire-resistant |
| Wood Frame with Brick Veneer | $250-$350 per sq ft | Brick ranch homes where matching the exterior is critical for resaleExcellent curb appeal, matches brick first floors seamlessly, very durable |
| Structural Insulated Panels (SIPs) | $220-$320 per sq ft | Energy-conscious homeowners in climate extremes who want long-term utility savingsSuperior insulation, faster framing, energy-efficient, airtight construction |
| Modular / Prefab Second Story | $130-$220 per sq ft | Straightforward rectangular footprints where speed and cost control are prioritiesFactory-built sections reduce on-site time, weather exposure, and labor costs |
Other Projects in St. Louis
St. Louis Estimate
Typical Range
$100,931-$302,793
vs. National Average
1% above national
Cost Multiplier
1.01x
Cost Per sq ft
$151-$404
This 1.01x estimate prices St. Louis labor from BLS Occupational Employment and Wage Statistics (May 2025) and applies a lighter regional adjustment to materials and permits, which vary less by metro than labor does. Actual bids vary by contractor, project scope, and timing.
See national average costs →