What is the difference between site-built and pre-fabricated plans? #
Site-built ADUs, also called stick-built, are built from scratch using traditional construction methods. This option allows for a lot of customization and smaller changes to be made throughout the construction process.
Prefabricated ADUs, also called Prefab, Manufactured, Modular, or sometimes Panelized, are built in a factory, then shipped to the site to be assembled or placed on a foundation. These units typically offer less flexibility and customization options, but often have a more streamlined process and fewer hidden costs and risks.
We require prefabricated plans to have state or federal certification. If your prefab design is not eligible for these approvals, please contact us at designer@aduaccelerator.org to move forward. Note that many panelized designs may be considered site-built instead of prefabricated.
What is the difference between types of prefabricated ADUs? #
Modular: Different parts of the ADU are built and inspected off-site, and either assembled off-site or assembled in large modules on the foundation using a crane or tow.
Manufactured: The ADU is built and inspected for building code off-site at a factory. It is then delivered and put in place on your property by either a crane or tow. Local inspectors only check work like foundation and utility hook-ups.
Panelized: Some or parts of the ADU are built off-site at a factory and assembled on-site. We currently require all prefabricated ADUs to be approved by HUD or HCD and require no local inspections, making this option uncommon. If your panelized ADU requires local inspections and/or does not have HUD or HCD inspections, we recommend listing it as site-built.
