Factory-Built ADUs in Stanislaus County, CA

10/13/2026

If you own a home in Modesto, Salida, Oakdale or elsewhere in Stanislaus County, there may be room on your lot for a second home: an accessory dwelling unit, or ADU. Families add them for aging parents, grown kids or rental income. This post covers the California ADU basics from official sources, how a factory-built ADU goes from permit to move-in, and one compact home from Baxter Homes, Inc. in Salida that's worth a look.

What counts as an ADU in California

The California Department of Housing and Community Development (HCD) publishes an ADU Handbook (the current edition is dated March 2026). It defines an ADU as an attached or detached home with complete, independent living facilities for one or more people: permanent provisions for living, sleeping, eating, cooking and sanitation, on the same lot as an existing or proposed primary residence.

A common question is whether a manufactured home can be an ADU. HCD's answer is a plain "yes." By definition, an ADU includes a manufactured home as defined in the state Health and Safety Code. That means a factory-built home can be your backyard unit. It doesn't have to be stick-built on site.

Here are a few state rules from the handbook that shape most projects:

• 60-day decision. If there's already a house on the lot, the permitting agency must approve or deny a complete ADU application within 60 days. If it denies one, it must send written comments explaining what to fix.
• Size. Local governments can set maximum sizes, but they must allow at least 850 square feet of interior living space, or 1,000 square feet for an ADU with more than one bedroom. Where a local ordinance doesn't comply with state law, a new detached ADU can be up to 1,200 square feet.
• Setbacks. Local rules can't block an ADU of at least 800 square feet with four-foot side and rear setbacks.
• Impact fees. An ADU with 750 square feet of interior living space or less is exempt from impact fees. Larger ADUs can be charged fees in proportion to the size of the main house.
• Owner-occupancy. Apart from a narrow exception for ADUs sold separately, local agencies can't require you to live on the property to build an ADU.

The handbook covers more, including parking, height limits and junior ADUs. Your local building department applies these rules to your lot, so start there.

Stanislaus County's ADU rules and free plans

For unincorporated areas like Salida, Stanislaus County Planning allows ADUs in several zoning districts, including R-1, R-2, R-3, R-A, residential planned-development districts and A-2 general agriculture. You need a building permit first, and the county says only a property owner or a licensed contractor (not a tenant) can be issued one. Applications can be filed online or at the county office at 1010 10th St in Modesto.

The county also offers free pre-drawn ADU plans for detached new construction to property owners in unincorporated Stanislaus County and in Ceres, Hughson, Modesto, Newman, Oakdale, Patterson, Riverbank, Turlock and Waterford. Those plans are for site-built units. If you'd rather have a factory-built home, that's a different route, covered below.

Modesto and Oakdale have their own city building departments. Manteca is across the line in San Joaquin County and runs its own permit process too. Requirements vary by jurisdiction, so check with the office that covers your parcel before you settle on a plan.

How a factory-built ADU comes together

With a factory-built ADU, most of the home is built indoors at the plant while your site is prepared, so the two jobs run side by side. Baxter Homes sells homes built by Skyline in Woodland, California, and handles everything on your side.

Baxter Homes is a full-service modular home retailer and a general contractor. It holds a C-47 manufactured home contractor's license and a general building contractor's license (License No. 1057475; Dealer License DL1113076). In the company's own words, it's a "one-stop shop" that handles everything from pulling permits to delivery and installation.

In practice, you start by picking a floor plan that fits your lot and the local size and setback rules. Because Baxter Homes is a licensed contractor, it can pull the permits instead of leaving you to work through the county or city on your own. Skyline then builds the home in Woodland while the foundation and utility work go in at your property. Finally, the home is trucked in, set, and connected.

Ask the office about timing and what's included for your specific lot. Site work varies a lot from one backyard to the next.

A compact option: the Elmore Bay (A)

If you want a full-size home that still fits a typical backyard, look at the Elmore Bay (A). It's listed at $130K, with 3 bedrooms, 2 baths and 1,026 square feet in a 23'4" x 44' footprint.

One thing to know: 1,026 square feet is above the 850 and 1,000 square-foot minimums that state law makes every city and county allow. Some jurisdictions allow larger ADUs, and some don't. Because it's over 750 square feet, impact fees may also apply. Confirm the size limit for your parcel before you commit, and Baxter Homes can help you check. You can browse more ADUs and floor plans on the site.

Talk to a local, family-owned team

Baxter Homes, Inc. is a small, family-owned business with over 30 years in the modular home industry, and it specializes in custom design, construction and installation of modular homes, ADUs and tiny homes. If you're thinking about an ADU in Modesto, Salida, Oakdale, Manteca or nearby, stop by the office at 4654 Salida Blvd, Salida, CA 95368, call (209) 303-1105, or send us a message. Have your parcel address handy so the team can help you work out what fits.