Prefab ADUs

Prefab ADU companies in the Bay Area: who to compare first

Prefab ADUs can look simple online. The hard part is knowing which company handles the full project, which one only sells plans, and what your lot still needs.

Published August 7, 2026

This is a homeowner-first research page. It is not a paid ranking. A company is listed here because it appears in San Jose official preapproved ADU sources, Bay Area prefab ADU searches, or local Google Maps ADU data.

Use it as a first screen. Before you sign, ask each company what is included, what is excluded, who pulls the permit, and who is responsible for construction.

What to compare

  • Is the company a plan vendor, prefab manufacturer, dealer, contractor, or design-build firm?
  • Does the price include foundation, utilities, delivery, permit work, and site repair?
  • Does the company have San Jose or Bay Area permit experience?
  • Who answers city comments if the plan is not accepted the first time?
  • Can you see finished ADUs, not only renderings?

San Jose preapproved ADU vendors

San Jose says preapproved ADUs use standard plans that city staff have already reviewed for code compliance. The city also says applicants still need a site-specific plan that shows where the ADU will go.

That means a preapproved plan can help, but your lot still matters. Access, slope, trees, utilities, fire rules, and panel upgrades can still change the project.

See the deeper homeowner guide here: San Jose preapproved ADU plans.

Companies to compare first

VitalizeBuild / Basically Homes

San Jose preapproved ADU plan under review

Listed by the City of San Jose as Basically Homes, powered by VitalizeBuild Construction, with a pending 499 sq. ft. 1 bedroom 1 bath ADU plan.

What to verify: Ask whether the plan is now approved, who pulls the permit, what site work is included, and whether the quoted price includes utilities.

CityPaks

San Jose preapproved ADU plans under review

Listed by the City of San Jose with several pending studio, 1 bedroom, and 2 bedroom ADU plans.

What to verify: Ask which plans are approved today, whether changes remove the fast-track path, and who handles the site-specific package.

SYMBiHOM

Garage conversion ADU or JADU plan under review

Listed by the City of San Jose with a pending 440 sq. ft. garage conversion ADU or JADU plan.

What to verify: Ask whether your garage qualifies, what happens if the slab or ceiling height needs work, and who handles construction.

H2 Prefab

Bay Area prefab ADU company to verify

Appears in Bay Area Google Maps data as H2 Prefab with a prefab-focused website and low public review volume.

What to verify: Ask for total installed cost, model availability, permit responsibility, and who performs site work.

ExpandADU

Fremont prefab ADU company to verify

Appears in local Google Maps data as ExpandADU | Prefab ADUs, with a Fremont location and prefab ADU positioning.

What to verify: Ask whether they serve your city, how delivery and access are handled, and what is excluded from the first price.

LiveLarge

San Jose preapproved ADU vendor

Listed by the City of San Jose with a 795 sq. ft. 2 bedroom 2 bath preapproved ADU plan.

What to verify: Ask about final installed cost, whether the standard plan can change, and who coordinates the city submittal.

Ca2Homes / UniADU

San Jose preapproved ADU vendor

Listed by the City of San Jose with 499 sq. ft. and 747 sq. ft. preapproved ADU plans.

What to verify: Ask whether UniADU handles only plans or also construction, site work, permit pulling, and inspections.

J. Kretschmer Architect / GetADU

San Jose preapproved ADU vendor

Listed by the City of San Jose with 748 sq. ft. and 476 sq. ft. preapproved ADU plans.

What to verify: Ask whether you need a separate builder, what plan changes are allowed, and how the site-specific plan is prepared.

Epic Modulars

San Jose modular home dealer to verify

Appears in San Jose Google Maps data as Epic Modulars, a modular home dealer with low public review volume.

What to verify: Ask who is the licensed contractor of record, what the dealer handles, and what parts of the project are outside the module price.

Fast Struct

San Jose modular home builder to verify

Appears in San Jose Google Maps data as Fast Struct, a modular home builder with modest public review volume.

What to verify: Ask whether their ADU path is prefab, modular, or site-built, and ask for a written list of excluded costs.

Unit price is not the full project price

Many prefab ADU pages lead with the unit price. That can be useful, but it is not the same as total installed cost.

Ask about delivery, crane access, foundation, utility trenches, sewer, water, electrical panel upgrades, permit fees, inspections, appliances, and landscaping repair.

Read the deeper guide here: Prefab ADU San Jose costs.

How to use this list

  1. Pick two or three companies that match your lot and budget.
  2. Ask whether they handle plans, permits, construction, or only part of the project.
  3. Ask for a written list of exclusions.
  4. Compare the total installed cost, not only the online price.
  5. Use the quote checklist before signing.

If you are comparing a prefab company with a contractor or architect, read ADU contractor vs architect.

Official and research sources

Frequently asked questions

What is the best prefab ADU company in the Bay Area?
There is no single best company for every lot. Compare the total installed cost, site work, permit responsibility, finished photos, and who is legally responsible for construction.
Are San Jose preapproved ADUs already approved for my lot?
No. San Jose says preapproved ADUs use standard plans, but applicants still need a site-specific plan and complete documents.
Should I choose prefab or custom for a San Jose ADU?
Prefab can help when your lot is simple and the standard plan fits. Custom can be better when privacy, access, design, or site limits need more care.

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