Are Pre-fab ADUs Cheaper Than Stick Built ADUs?

The advantage to using a pre-fab ADU is that it can be quicker than a stick build ADU. Because they are fabricated in a factory, they are made faster and dropped onto your lot.

You would be saving on having new architectural plans drawn up. But either way, you still need a permit to build, and the savings if any is minimal compared to what you are compromising on.

What they don’t usually provide for you is all of the customization you can get with a stick built ADU. You may be able to make a few choices for your fixtures and finishes, but they will be limited. And you will also be limited by where the windows and doors can be placed, how they swing open, whether the doors can be pocket doors instead of swing doors, or can they be sliders. Also, choosing your ceiling height, with beams on the ceiling. Or selecting your baseboards, crown molding, and other millwork. Of course, you want to choose your flooring, paint colors, plumbing and electrical fixtures. 

Costs:

Prefab (factory built) in California 2026 is usually around $150-280K for the unit, but when including the installation (site preparation, foundation, and utility connections) can be as much as $200-350K.

Stick Built cost $180-400K depending on size, location and finish level.

Site Considerations:

Prefabs are ideal for lots that have a flat backyard, driveway access wide enough for a truck, no overhead obstructions, and standard rectangular setback footprint.

 If a crane can’t reach your lot, you’re looking at $15-30K in alternative rigging, or switching to stick build.

Building Codes and Permits:

Both prefab and stick built ADUs must meet the same California building code requirements, pass the same inspections, and obtain the same permits. Prefab is not a regulatory shortcut.

 Timeline:

A prefab ADU takes 17-48 weeks total, while a stick build ADU takes 26-64 weeks total. This includes design & engineering, permitting, manufacturing/construction, and site work/installation.

 The right choice depends on your lot, your budget, and how important customization is to you. For some homeowners, a prefab ADU makes sense. For others, the flexibility of a stick built ADU is well worth the additional investment and time in order to have the exact design that they want.

 Décor Revolution is accredited as an ADU specialist. If you are interested in having us design an ADU for you please reach out.