The Short Version.
A stick-built ADU is constructed piece by piece on your property by a general contractor and subcontractors, under local plan review and inspections. A modular (factory-built) ADU is manufactured indoors to California state-approved plans, then delivered finished and craned onto a prepared foundation. The construction method changes three things that matter: how long it takes, how certain the price is, and how consistent the quality is.
Side By Side.
| Modular (Abodu) | Custom Stick-Built | |
|---|---|---|
| Timeline | Months, not years: factory build runs parallel to site prep; installed in as fast as one day | Commonly 9 to 16 months of sequential on-site phases |
| Price Certainty | Fixed all-in price set before construction starts | Bids plus change orders; budgets routinely move mid-project |
| Quality Control | Indoor factory construction, repeatable process, state oversight | Depends on crew, weather exposure during framing, and site conditions |
| Approvals | State-approved plans; the city reviews your site, not the building | Full local plan check and phase-by-phase inspections |
| Weather Risk | None during construction; the building is built indoors | Every storm delays framing and cascades through schedules |
| Site Disruption | Weeks of site prep, one crane day | Months of trades, deliveries, and noise in your backyard |
| Customization | Curated models, finishes, and options | Unlimited: any design your architect can draw |
| Lot Constraints | Needs crane access to the backyard | Can build where a crane can't reach; attached units and conversions |
Where Stick-Built Genuinely Wins.
We'll say it plainly. Choose a custom site build if you need an attached ADU or garage conversion, if your lot has no crane path (dense infill with no street or neighbor access), if you want fully bespoke architecture matched to the main house, or if your site needs unusual engineering a standard foundation can't solve. A good general contractor is the right partner for those projects.
Where Modular Wins, And By How Much.
For a detached backyard home on a reachable lot, the modular math is hard to argue with: a fixed price instead of change-order roulette, a building that's weatherproof from day one of construction, state-level plan approval that shortens permitting, and an install measured in hours instead of seasons. Our California cost guide puts real numbers on the comparison, and the Fixed Pricing page shows exactly what's in an Abodu price.
The Site-Cost Truth Both Sides Share.
Every ADU, however it's built, needs a foundation, utility connections, and site access. Beware of any comparison, in either direction, that pretends site work doesn't exist. The honest difference is when you learn the number: Abodu quotes site-specific work after a site assessment and before you sign. Custom builds price it as they discover it.