Does Bay Modular publish an HCD number?

Yes. Bay Modular publishes HCD #1585366 on its public website. Homeowners should still confirm model-specific approval and the local site permit path.

Are Bay Modular model prices the full project cost?

Not by themselves. Bay Modular's model page lists starting prices and separately notes that delivery, heavy machinery installation, foundation, and infrastructure work are not included in those model prices.

Is Bay Modular a recommendation?

No. This is a source-backed research profile. Homeowners should verify current service area, local contractor model, site costs, permit scope, and finished project examples.

Company Research

Bay Modular ADU in the Bay Area: HCD, costs, and questions

Bay Modular publishes strong HCD and model-cost signals, but homeowners still need to separate unit price from delivery, installation, foundation, utilities, and site-specific permits.

Published August 16, 2026

This is a homeowner research profile. It is not a paid placement, review, or recommendation.

Bay Modular presents itself as a prefab and modular ADU company serving the Bay Area, Oakland, San Francisco, San Jose, and nearby markets. The company publishes a factory visit location in Lathrop, California and HCD #1585366.

That makes Bay Modular useful to compare when a homeowner wants a source-backed modular option instead of a vague online prefab quote.

What to verify first

Which Solo model is currently HCD-approved or inspected for California use?
Which local permits are still required for foundation, site plan, and utilities?
Who manages local contractors for concrete, plumbing, electrical, and solar?
What is the full installed cost after delivery, crane or machinery, and infrastructure?
Can Bay Modular show finished projects in your city or nearby Bay Area cities?

Why this company is worth a first screen

Bay Modular has unusually specific public information for a prefab ADU company. Its site describes a full-service package, publishes an HCD number, and gives model-level pricing context for the Solo ADU series.

It also states that local foundation plans, site plans, and utility connections remain subject to local building department inspection and review.

Unit price versus project price

Bay Modular's model page lists public starting prices for Solo models. It also says site preparation costs are not included, including delivery, installation with heavy machinery, foundation, and infrastructure work.

The same public page gives an approximate delivery, craning, and infrastructure range of $40,000 to $60,000 for Solo 2, 3, and 4. Treat that as a planning prompt, not a final estimate for your lot.

Tight access, trenching distance, panel upgrades, drainage, fire requirements, surveying, and city comments can still change the total.

Questions to ask Bay Modular

Which Solo model fits my city, lot size, setbacks, and access?
What exactly does HCD #1585366 cover for my selected model?
Who prepares the site plan, foundation plan, and utility drawings?
What local permits are still required?
Who hires and manages concrete, plumbing, electrical, solar, and crane vendors?
What costs are excluded from the listed model price?
Can I see finished Bay Area projects and final project scopes?
Who is responsible for warranty service after installation?

Related comparison pages

Compare this profile with the Bay Area prefab ADU company guide, the prefab ADU manufacturer guide, and Prefab ADU San Jose costs.

For Bay Modular

If you represent this prefab ADU manufacturer, send corrections, current availability, project examples, license or code-path details, profile review requests, or sponsored visibility questions through the ADU company submission page.

For broader participation details, see the builder and prefab company contact page. Paid visibility is clearly labeled and kept separate from editorial recommendation. Use the ADU advertising page for sponsorship details.

Sources

Frequently asked questions

Does Bay Modular publish an HCD number?: Yes. Bay Modular publishes HCD #1585366 on its public website. Homeowners should still confirm model-specific approval and the local site permit path.
Are Bay Modular model prices the full project cost?: Not by themselves. Bay Modular's model page lists starting prices and separately notes that delivery, heavy machinery installation, foundation, and infrastructure work are not included in those model prices.
Is Bay Modular a recommendation?: No. This is a source-backed research profile. Homeowners should verify current service area, local contractor model, site costs, permit scope, and finished project examples.

Comparing Bay Modular with other prefab ADU options?

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