What's Included in an ADU Price in Hayward, CA

10/26/2026

If you're thinking about adding a backyard home in Hayward or elsewhere in Alameda County, the first number you'll see is a floor plan's price. That number is a starting point, not a final budget. This guide from Green Galaxy Homes explains what a listed ADU price usually covers, which costs show up later, how California's ADU fee rules can work in your favor, and what Hayward asks for when you apply.

Green Galaxy Homes is based in Santa Clara and works on manufactured and modular homes and accessory dwelling units (ADUs) for California properties. Here's how we'd read an ADU price if we were in your shoes.

Start with the listed price

Our floor plans show a price range for each home. For example, the CM-1482D is a 2-bedroom, 1-bath plan with 560 square feet listed at $84K–$93K. The CM-2562L is a 2-bedroom, 1-bath plan with 747 square feet listed at $94K–$104K. The CM-6622L is a 3-bedroom, 2-bath plan with 889 square feet listed at $104K–$115K.

The floor plan pages don't spell out whether site work, foundation, utility connections, delivery, installation or local fees are part of those ranges. Every backyard is different, so those items depend on your lot and your city. Ask for each one as its own line in your quote.

What our building process covers

Our Building Process page lays out four stages:

• Planning. We contact the building and planning departments to gather information from your local jurisdiction.
• Designing. Our design team assesses and designs your project to comply with your property access and unique building requirements, and you choose the home's interior and exterior features.
• Permits. Your project coordinator gathers the plans and documents needed to obtain a building permit.
• Construction. We provide bids based on the engineered plans and the permit package, and construction contracting, management, scheduling and coordination of all construction is included in our services.

As our ADUs & Backyard Homes page explains, we've partnered with local engineers, architects, energy consultants and general contractors. The construction bid comes after the plans are engineered and the permit package is ready, so the full number reflects your actual site.

California's ADU fee rules

State law has a direct effect on ADU budgets. According to the California Department of Housing and Community Development's ADU Handbook (updated March 2026), an ADU with 750 square feet of interior livable space or less is exempt from impact fees charged by local agencies, special districts and water corporations. If an ADU has more than 750 square feet of interior livable space, impact fees must be charged proportionately to the square footage of the primary dwelling. The handbook also notes that school districts may charge fees on ADUs larger than 500 square feet of interior livable space, and it confirms that a manufactured home can be an ADU under state law.

For the plans above, that matters. A 560-square-foot CM-1482D or a 747-square-foot CM-2562L is in the size range where the impact-fee exemption can apply, while the 889-square-foot CM-6622L is above the 750-square-foot line. Ask the city how it measures interior livable space, since listed square footage and the figure used for fees may not match exactly. Impact fees are only one kind of fee, too. Permit, plan-check and utility fees can still apply.

How the process works in Hayward

Inside Hayward city limits, ADU applications go through the city's ADU and JADU permit page. The city asks you to contact a planner first to confirm your site is eligible, then register for an e-Permit Portal account and apply online. A custom ADU submittal includes construction documents (site plan, floor plans, elevations, sections, details and a Title 24 energy report) plus the city's ADU checklist. A plan review fee is due before review, and other permit fees are due when the permit is ready to issue. The city's ADU process handout adds a few budget items worth asking about. It says total fees generally range from $6,000 to over $25,000 depending on the ADU's size and type, with new detached ADUs at the high end, and that fees are subject to change. It also notes that water and sewer connection or capacity fees may apply, and that new detached ADUs must be all electric with no new gas connection. That last point is worth raising early, since some floor plans list gas appliances as standard. The handout is a few years old, so confirm current fees and rules with the city's planning staff before you budget.

If your lot is in Fremont, unincorporated Alameda County or another city, check with that jurisdiction directly. Local rules and fees differ from city to city.

Questions to ask about any ADU price

Before you compare ADU quotes, ask each company whether the price covers the home only or includes delivery and installation. Ask who handles the foundation and site prep, and which utility connections are included for water, sewer and power. Ask whether the home can be configured all electric if your city requires it. Find out who prepares the plans and permit package, and who pays the permit, plan-check and utility fees. And ask how the home's interior livable space compares to the 750-square-foot impact-fee threshold.

Start with your property

Green Galaxy Homes is at Parkway Plaza, 4655 Old Ironsides Dr, Santa Clara, CA 95054. Browse our floor plans, read about our building process, and contact us to talk through what an ADU on your Hayward lot would include.