Modular building sizes in California, at a glance: exact dimensions, module counts, and current availability for offices, portable classrooms, and other buildings — plus how the state’s HCD and DSA approval processes work for private and public projects. Looking for the bigger picture first? See our general guide to modular building types and sizes.
Sizes are grouped by use below. Most private-sector buildings in California — schools, churches, and businesses — are approved through the state’s HCD (Department of Housing and Community Development) process; public K–12 campuses go through the more involved DSA (Division of the State Architect) process instead. The “Typical Occupancy” column shows the default California Building Code (CBC) occupancy class for that use — classrooms are usually Group E, offices Group B — but the legal occupancy is always confirmed per project, since a used classroom can be recertified from E to B when it’s converted to office space.
Classrooms
| Size | Approx. Square Feet | Modules | Typical Occupancy | Common Uses | Get a Price |
|---|---|---|---|---|---|
| 12′ x 40′ | 480 | 1 | E or B | Single-wide classroom or small office | Get a Price |
| 24′ x 40′ | 960 | 2 | E | Standard double-wide classroom — the most common size in California | Get a Price |
| 24′ x 60′ | 1,440 | 2 | E or B | Double classroom or open office | Get a Price |
Offices & Multi-Room Complexes
| Size | Approx. Square Feet | Modules | Typical Occupancy | Common Uses | Get a Price |
|---|---|---|---|---|---|
| 8′ x 40′ | 320 | 1 | U or B | Storage or small single-person office | Get a Price |
| 10′ x 40′ | 400 | 1 | B | Compact office trailer | Get a Price |
| 10′ x 56′ | 560 | 1 | B | Office trailer | Get a Price |
| 12′ x 60′ | 720 | 1 | E or B | Single-wide office — fits a restroom comfortably | Get a Price |
| 20′ x 32′ | 640 | 2 | B | Small double-wide office | Get a Price |
| 28′ x 60′ | 1,680 | 2* | B | Multi-room office with restrooms and a break room | Get a Price |
| 36′ x 56′ | 2,016 | 3 | B | Large multi-room office, 2 ADA restrooms, wet bar | Get a Price |
| 36′ x 60′ | 2,160 | 3 | B | Triple-wide office, break room, M/W restrooms | Get a Price |
| 48′ x 60′ | 2,880 | 4 | B | Office/admin complex, break room, M/W ADA restrooms | Get a Price |
| 60′ x 60′ | 3,600 | 5 | B or F | Office/training complex with kitchen and restrooms | Get a Price |
| 72′ x 60′ | 4,320 | 6 | B or F | Large office/industrial complex with locker rooms, showers, restrooms, and kitchen | Get a Price |
* The 28′ x 60′ is built from two 14′-wide modules rather than the standard 12′-wide module — that extra width requires an oversize permit plus pilot/escort vehicles and a restricted midday travel window under California transport rules, which adds cost and schedule versus a standard 12-wide building of similar size.
Restrooms, Showers, Locker Rooms & Break Rooms
We don’t sell these as stand-alone buildings — in California’s private-sector market they’re almost always built into a larger office or complex, plumbed and finished as part of that building. Here’s where they show up in the sizes above:
- 12′ x 60′ single-wide — comfortably fits one restroom alongside office space
- 28′ x 60′ — multiple offices plus restrooms and a break room
- 36′ x 56′ and 36′ x 60′ — two ADA restrooms, plus a break room (the 36’x60′ break room typically includes an ice maker)
- 48′ x 60′ — break room plus men’s/women’s ADA restrooms
- 60′ x 60′ — restrooms, showers, and dressing area alongside training and kitchen space
- 72′ x 60′ — the largest configuration, with locker rooms, showers, restrooms, and a kitchen for industrial workforce use
Need a specific stall or shower count for a project? Call (800) 806-7485 and we’ll confirm exact fixture counts against current inventory and floor plans.
Specialty
| Size | Approx. Square Feet | Modules | Typical Occupancy | Common Uses | Get a Price |
|---|---|---|---|---|---|
| 8′ x 20′ | 160 | 1 | U | Guard shack, kiosk, or ticket booth | Get a Price |
Medical, clinic, and laboratory buildings are typically built out from the office sizes above with special finishes and utility connections rather than sold as a separate size class — call to discuss your specific requirements.
Get pricing for your California project
Call us at (800) 806-7485 to talk through sizing and availability today, or request pricing online and we’ll follow up with real numbers for your project. Want a step-by-step permitting checklist too? Get our free HCD permit guide.
iModular.com — California modular building specialists since 1998. Last updated: September 9, 2026.