0Frequently Asked Questions
Accessory Dwelling Unit (“ADU”)
What is an Accessory Dwelling Unit (“ADU”)?
An Accessory Dwelling Unit (“ADU”) is a detached or attached structure 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 or a garage can be converted to an ADU. USModular, Inc. specializes in DETACHED ADUs built with prefabricated construction as we find this to be the fastest and most cost-effective method to build a detached ADU
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 websites: When appropriate, you can schedule to meet with us and view 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, waving some development fees and reducing permit processing time. The State of California allows for a 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 800 sf as long as you meet the local jurisdiction setbacks.
What is prefabricated construction?
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 construction to be a Better, Faster, Greener way to build and Less Expensive than the traditional site-built construction method.
How does prefabricated construction differ from traditional site-built construction?
Prefabricated and site-built ADUs are built with the SAME materials. Factory built construction allows for efficiencies in the overall process that realizes significant cost and time savings over traditional site construction methods.
Prefabricated ADU: built indoors in a factory by skilled tradesman 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, we can complete site work (grading and utility and foundation prep at 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: built onsite by a contractor and many sub-contractors with local building department onsite inspections during the ongoing construction. Inefficient method of construction due to scheduling of sub-contractors, weather delays and limited quality control. Much longer site disruption.
With 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:
What is the “all-in” price for a detached ADU?
There are a lot of factors when 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.
Starting at “all-In” pricing for USModular, Inc. detached ADU projects:
- 400 SF to 750 SF STARTING AT $160,000
Pricing is subject to change without notice and subject to material availability.
The starting at price includes Design, Permits/Fees, Raised Pier Foundation, Fabrication, Transportation, Roll Set, Install the ADU, Utility Connections to existing.
These prices are based on an ADU built to Federal Building Code and a flat accessible lot within USModular, Inc.’s service area. Cost may vary depending on site conditions, lender requirements, local jurisdiction requirements, accessibility to ADU site and location of utilities.
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 with combine experience of the company principals and key employees of over 100 years building with prefabricated construction. USModular, Inc. provides all services necessary to complete your new home from design, to permitting, to fabrication, to site work and installation of your detached Accessory Dwelling Unit. We offer a complete turn-key ADU construction project.
Do you offer model tours?
We have built ADUs throughout many areas of Southern California. We can give you an address of a finished ADU so you can you drive by 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 to build 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 property and provide a site plan and budget based on the lot requirements and the size ADU you would like.
Can I get a PROJECT COST estimate without paying for a site visit?
Yes!! We offer a complementary virtual project site review using Google Earth. To have us provide you with the free site evaluation and preliminary project cost click on this link: USM-ADU Preliminary Review
How can I contact USModular, Inc.?