By building type and finish tier — August 2026
Cost per square foot is the number everyone asks for and the number most easily abused. A quote of "$180 a foot" is meaningless without knowing whether it includes the foundation, the freight, the permit, the crane, and the finish level. Ours does not — every figure on this page is structure only, delivered as a finished module, and site work is priced separately so you can see it.
Three things move the number more than anything else. Finish tier is the largest single lever and it is a genuine choice rather than a trick — the same shell with commercial LVP and stock cabinetry versus architectural millwork and stone is a real spread. Fixture count matters far more than floor area, which is why a 120 sq ft restroom building can cost more per foot than a 1,200 sq ft home. And size works in your favour: fixed costs spread, so the per-foot number falls as the building grows.
| Tier | Base rate | What you get |
|---|---|---|
| Essential | $265/sq ft | Clean, durable factory finishes. Everything you need, nothing you don't. |
| Signature | $325/sq ft | Designer interiors, upgraded fixtures, premium cabinetry. |
| Premium | $395/sq ft | Architectural-grade finishes, custom millwork, luxury fixtures. |
| Type | Essential | Signature | Premium | Typical size |
|---|---|---|---|---|
| Accessory dwelling unit (ADU) | $265 | $330 | $395 | 385–1,200 sq ft |
| Modular home | $245 | $310 | $375 | 900–2,400 sq ft |
| Modular office | $210 | $270 | $330 | 320–2,000 sq ft |
| Mobile / jobsite office | $185 | $235 | $285 | 160–800 sq ft |
| Modular classroom | $205 | $257 | $310 | 600–1,800 sq ft |
| Modular medical / clinic | $340 | $430 | $520 | 800–3,000 sq ft |
| Guard booth | $420 | $700 | $980 | 16–120 sq ft |
| Restroom building | $380 | $495 | $610 | 80–600 sq ft |
| Container conversion — office | $115 | $145 | $175 | 160–320 sq ft |
| Container conversion — living | $215 | $277 | $340 | 160–320 sq ft |
Installed cost of the module itself, on top of the structure rate.
| Module | Dimensions | Area | Installed cost |
|---|---|---|---|
| Full Bathroom | 8×7 ft | 56 sq ft | $18,500 |
| Half Bath | 5×5 ft | 25 sq ft | $11,000 |
| Full Kitchen | 12×9 ft | 108 sq ft | $27,500 |
| Kitchenette | 8×6 ft | 48 sq ft | $14,000 |
| Primary Bedroom | 13×12 ft | 156 sq ft | $16,800 |
| Bedroom | 11×10 ft | 110 sq ft | $12,500 |
| Living / Great Room | 14×13 ft | 182 sq ft | $9,500 |
| Office / Den | 10×9 ft | 90 sq ft | $10,200 |
| Laundry | 6×5 ft | 30 sq ft | $4,800 |
| Utility / Mechanical | 5×4 ft | 20 sq ft | $3,600 |
| Loft | 10×10 ft | 100 sq ft | $11,500 |
| Covered Deck | 12×8 ft | 96 sq ft | $8,064 |
| Cabinet Run (8 ft) | 8×2 ft | 16 sq ft | $3,200 |
These are the line items a configurator actually adds up. A bathroom costs what it costs because of the fixtures, the waterproofing, the mechanical ventilation and the DWV rough-in — not because of its floor area. The same logic explains why a kitchen is the single most expensive module in any small building.
Cost per square foot is a useful comparison tool and a terrible budgeting tool, and the distinction matters. It is useful because it normalises across building sizes and lets you compare two sellers on roughly equal footing. It is terrible for budgeting because the denominator is floor area while a substantial share of the cost has nothing to do with floor area at all.
Consider two 400 square foot buildings. One is an open jobsite office with a single restroom, four windows and one mechanical unit. The other is a two-bedroom dwelling with a full kitchen, a full bath, a laundry closet and a mechanical system sized for continuous occupancy. Identical floor area, and the second costs perhaps seventy percent more. Anyone quoting a single per-square-foot rate across both is either averaging away the difference or has not thought about it.
The rule of thumb worth internalising is that fixtures and mechanical equipment drive cost, and floor area drives very little of it. Adding two hundred square feet of bedroom to a design is comparatively cheap. Adding a second bathroom to the same design is not. This is why the most effective cost-reduction move in a small building is almost never shrinking it — it is reducing the fixture count or accepting a lower finish tier in the rooms nobody looks at.
The spread between Essential and Premium is roughly fifty percent on the structure rate, which is a large enough number that it deserves a clear explanation rather than adjectives.
Essential is commercial-grade and genuinely durable: luxury vinyl plank flooring, stock cabinetry with soft-close hardware, solid-surface counters, standard plumbing and lighting fixtures, painted drywall. Nothing about it is cheap in the sense of failing early. It looks like a well-built rental or a competent office.
Signature adds designer selection rather than more material: upgraded fixtures, better cabinetry with more interior fittings, tile in wet areas rather than vinyl, recessed lighting on dimmers, and interior finishes chosen rather than defaulted. This is the tier most owner-occupied units land on, and it is where the money is best spent for anyone who will live in the building.
Premium is architectural: custom millwork, stone or engineered stone counters, specified lighting, high-end appliances and fixture packages, and finish carpentry that takes real time. The cost is largely labour rather than material, which is why the increment is so large.
Mixing tiers is normal and sensible. Premium where it is seen and touched daily, Essential in the utility room. Nobody has ever regretted a stock closet.
If you are holding two per-square-foot numbers from two suppliers, they are almost certainly not measuring the same thing. Four questions resolve nearly every discrepancy.
Is the foundation in or out? At $38 to $52 per square foot this single question accounts for more apparent price difference than anything else. A quote including foundation will look dramatically worse against one that excludes it, while being cheaper.
Is freight in or out, and from where? A supplier three hundred miles away and a supplier two thousand miles away are not comparable on structure rate alone.
What finish tier is quoted, specified how? "Upgraded finishes" is not a specification. Ask for the flooring product, the counter material, the cabinet line and the fixture brand. Two quotes that differ by fifty percent frequently differ by exactly this and nothing else.
Is the square footage measured the same way? Some suppliers quote gross exterior footprint, others quote conditioned interior area. On a small building the difference between the two can be eight percent, which is enough to reverse a comparison.
Once those four are normalised, the remaining gap is real and is about product quality, engineering and margin. Before they are normalised, comparing the numbers is meaningless.
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