Looks like you are ready to build a Prefab ADU in Southern California!

USModular process to build an ADU in southern California helps to minimize the time and frustration usually associated with new construction:

Virtual Site Assessment
Site Assessment, Meeting and Budget Prep
Design /Options finalized
Contract Signed
Plans – complete and submit – to local building dept.
ADU Sales Order Finalized – Escrow opened
ADU fabrication
Permits issued
Site Construction begins – Foundation and Utilities
ADU delivery and Installation
Final Inspection
House Warming Party!

What are ADU Homes?

Accessory Dwelling Units, aka ADU homes, are detached or attached structures on your single-family or multi-family property that has an existing primary residential living structure. A detached ADU is commonly referred to as a granny flat, guest house, 2nd unit or casita. An ADU can also be built inside your house as a Jr. ADU. We at USModular, Inc. are ADU builders who are experts in constructing detached prefab ADUs in Southern California. We find this to be the fastest and most cost-effective method to add additional living space to your property.

Where can I see your ADU floor plans?

You can view floor plans, renderings and pictures of our predesigned, prefabricated ADUs by checking out our ADU floor plan catalog, customizing your future ADU using our online builder, or checking our partners at myadu4less.com for more information on our pre-built models.

Do all cities in California allow detached ADUs to be built?

The State of California passed laws in 2020 that make it easier to build a detached ADU, including reducing setbacks, waiving some development fees and reducing permit processing time. The State of California allows for the maximum size of a detached ADU to be 1,200 sq ft, and parking requirements have been eased.

Local jurisdictions have the right to impose greater restrictions on the maximum size of detached ADUs and to also limit the maximum number of bedrooms. Per State mandate, you can have an ADU BY RIGHT up to 850 sf as long as you meet the local jurisdiction setbacks.

Learn more about ADU regulations in the state of California and in your city.

What is prefabricated ADU construction in California?

Prefabricated means we build our ADUs off-site in a factory. We build Modular (Local Building Code) and Manufactured (Federal Building Code) ADUs. In our 35+ years of experience as a general contractor and real estate developer, we have found prefabricated ADU construction in California to be a Better, Faster, Greener, and less expensive way to build than the traditional site-built construction method.

How does a prefab ADU differ from one using traditional site-built construction?

Site-built and prefab ADUs are built with the SAME materials. Factory-built construction allows for efficiencies in the overall process, realizing significant cost and time savings over traditional site construction methods.

Prefabricated ADU: built indoors in a factory by skilled tradesmen on a production line (just like a car and the majority of items we use on a daily basis). The State of California reviews and approves plans and acts as building inspector in the factory. Building indoors on a production line is faster, increases quality, lowers costs and eliminates the chance of wet homes/mold. Time savings are achieved because state-approved plans are submitted to the Local Jurisdiction for a building permit, and we can complete site work (grading and utility and foundation prep at the SAME time the ADU is built in the factory).

With today’s circumstances, the typical time frame to complete a prefabricated ADU project is 6 to 9 months from permit submission to project completion with minimal project site disruption.

Site-Built ADU: this type of ADU is built on-site by a contractor and many subcontractors, with local building department inspections during the ongoing construction. This method of construction is inefficient due to the scheduling of subcontractors, weather delays and limited quality control. It also causes much longer site disruptions.

Under today’s circumstances, the typical time frame to complete a site-constructed ADU project is 9 to 18 months from permit submission to project completion, with notably longer project site disruption.

Factory-Built Construction vs Site-Built Construction Project Time Frame Schedule:

: Site Built vs. Modular

What is the “all-in” price for a detached prefab ADU in California?

Many factors are involved in determining “all-in “pricing, including site conditions, local development fees/ permits and utility locations. We have over one hundred plans from 400 sf to 1,200 sf, with available options that include Granite/Quartz countertops, 9’ sidewalls, coffered ceilings, air conditioning, tile showers and engineered/laminate flooring.

“All-in” prices for our prefabricated ADUs can vary depending on the model, size, upgrades, etc. We encourage you to check out our floor plans for affordable ADUs in California or use our online builder to customize and price your future ADU home.

Pricing is subject to change without notice

The starting price includes Design, Permits/Fees, Raised Pier Foundation, Fabrication, Transportation, Roll Set, Install the ADU, and Utility Connections to existing.

These prices are based on an ADU built to the Federal Building Code and a flat accessible lot within USModular’s service area. Cost may vary depending on site conditions, lender requirements, local jurisdiction requirements, accessibility to the ADU site and location of utilities.

Check out our current financing incentives and offers!

What services do you provide/can you complete everything from A to Z?

USModular, Inc. is a second-generation full-service general contractor and manufactured/modular home dealer, boasting over 100 years of combined experience among its principals and key employees in prefabricated construction. As an expert ADU builder, USModular, Inc. provides comprehensive services to complete your new home, including design, permitting, fabrication, site work, and installation of your detached accessory dwelling unit. We deliver a complete turn-key ADU construction project.

Do you offer model tours?

We have built modular ADUs throughout many areas of Southern California. We can give you an address for a finished ADU so you can drive by and see some of our finished projects. When appropriate, we have models available to tour on a limited basis. Talk to a USModular, Inc. representative to discuss a tour.

Can I customize my ADU to look more like my existing home?

USModular, Inc.’s prefabricated ADUs are well designed and look like most traditional site-built homes as they are built with similar materials. USModular, Inc. can typically match colors and style of most homes. We have many options available that can increase the “curb appeal” of your ADU including: dormers, porches, bay windows, board/batt, stucco, tile roofing, and solar.

Can you visit my project site to determine the feasibility and costs of building my detached ADU?

Yes!! We offer a site visit with one of our project specialists for a small fee that is credited to your signed construction contract to walk the property and provide a site plan and budget based on the lot requirements and the size prefab ADU you would like.