Junior Accessory Dwelling Unit (JADU)

Introduction

Junior Accessory Dwelling Units (JADUs) are a streamlined, low-impact way to create extra housing within an existing or proposed single-family home. Under Humboldt County Code § 314-69 and California Government Code § 65852.22, a JADU is a small, self-contained living space carved out of the primary residence’s footprint—often by converting a spare bedroom, attic, or attached garage. Because JADUs reuse space that already exists, they can be built quickly, inexpensively, and with minimal neighborhood change while still adding long-term rental or multigenerational living options. County rules treat JADUs as principally permitted wherever accessory dwelling units (ADUs) are allowed. A ministerial building-permit review—no discretionary hearing—is all that is needed, provided the unit meets the specific development standards summarized under Key Points below.

Minimum Documents for Permit Submittal

The following documents are required for all permit applications for a new JADU. If you are unsure what these documents are or how to get them see our Construction Documents page. It will describe what the document is, why it is required, and how you can get it.

Forms

Design Documents

  • Site Plan
  • Construction Plans
  • Energy Calculations

NOTICE: Other documents will likely be required depending on where and how complex of a structure you are building. For example, if your energy calculations specify a minimum photovoltaic (PV) size you will be required to submit PV plans. See the Construction Documents page to see if other documents may be required for your permit submittal.

Quick Steps to Permit Issuance

Follow the below steps to start a permit application for a new JADU.

  1. Register for an Accela account (see our Accela Support Resources).
  2. Upload your required documents (see our Accela Support Resources and Step 3 on First Time Applying for Building Permit).
  3. Move through step 4 Preliminary Site Inspection and step 5 Plan Check described on First Time Applying for a Building Permit webpage.
  4. Once the permit is issued use the Inspections page to schedule inspections and change your issued permit if necessary.

Key Points

  1. Size & location
    • Maximum 500 sq ft and wholly contained within the walls of the single-family dwelling (including an attached garage or other accessory structure)
    • Up to 150 sq ft of additional floor area is allowed only for ingress/egress expansions
  2. Access & fire safety
    • Must have its own exterior entrance that is separate from the main home’s front door
    • Side and rear setbacks must be adequate for fire-service access, as determined by the local fire authority or State Responsibility Area Fire Safe regulations
  3. State-law compliance
    • Every JADU must satisfy all requirements of Gov. Code § 65852.22, which—among other things—caps the floor area at 500 sq ft
  4. Number of units per lot
    • You may pair one JADU with one detached ADU on the same single-family lot, provided the JADU stays within the existing structure
  5. Utilities & fees
    • Because a JADU is inside the primary home, no separate utility connection or capacity fee may be required when it is created within existing space that meets § 314-69.05.3.8.1 standards