Junior ADU (JADU) Title 24 Checklist
Start with the Energy Code definition: a JADU is 500 square feet or less and sits entirely inside a single-family building. Then classify the space it takes over, list what the work actually touches, and document only those parts. A new house, a conditioned room and a garage each land in a different category.
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Match the unit to the definition
Section 100.1 describes a JADU as a dwelling unit of no more than 500 square feet, contained entirely within a newly constructed or existing single-family building. The plans should show a kitchen, an entrance separate from the building's main entrance and an interior entry to the main living area. Sanitation may be the unit's own or shared with the house.
Classify the space it takes over
- Part of a newly constructed house: new construction, like the rest of the house.
- A room that is already conditioned: an alteration under Section 150.2(b), regulated by the components changed.
- An unconditioned attached garage: newly conditioned space, so an addition under Section 150.2(a).
One project can be an alteration in one room and an addition in the next. The alteration versus addition page explains the split.
List what the work touches
- The separate entrance: an alteration that adds exterior door area must meet the door U-factor of Section 150.1(c)5, which is 0.20.
- New windows: up to 16 square feet of added glass is excused from the area caps, but the U-factor and SHGC limits still apply.
- A mini-split or other new equipment: depending on scope it can bring ECC-Rater field verification, including refrigerant charge.
- New or altered lighting meets Section 150.0(k); unaltered luminaires may stay.
Ventilation is the open item
A JADU that is an addition to an existing building is excused from the whole-dwelling airflow in Section 150.2(a)1C. The California Mechanical Code can still require ventilation and may point back to Section 150.0(o), so the Energy Commission sends those questions to HCD.
Forms
A prescriptive alteration uses CF1R-ALT-01-E in the compliance manual's Appendix A list (its chapter 9 names CF1R-ALT-02-E, so confirm with the building department), or CF1R-ALT-05-E without field verification, and the addition part uses CF1R-ADD-01-E. Planning limits are on California ADU rules, the basics on does a JADU need Title 24, and the garage case on the garage conversion checklist. Start a report on the ADU page.
Common Title 24 Questions
- Do ADUs need Title 24 in California?
- What plans are needed for an ADU Title 24 report?
- How much does an ADU Title 24 report cost?
- How long does an ADU Title 24 report take?
- Does a garage conversion ADU need Title 24?
- Does a JADU need a Title 24 report?
Frequently Asked Questions
Yes. A JADU built as part of a newly constructed building must meet the new-construction requirements, according to the Energy Commission ADU FAQ.
The Energy Code definition allows it: a JADU may have its own sanitation facilities or share those of the single-family building.
Not under Section 150.2(a)1C when it is an addition. The Mechanical Code may still require it, so check with the building department or HCD.
Explore ADU and JADU
- New Detached ADU Title 24 Checklist
- Do Pre-Approved ADU Plans Come With Title 24?
- Does a Prefab ADU Need Title 24?
- Prefab and Factory-Built ADU Title 24 Requirements
- Two-Story ADU Title 24 Requirements
View all ADU and JADU guides → · Permits and Compliance · Title 24 guide