Thinking about adding a backyard casita in Dewey-Humboldt? With the right lot and a clear plan, an accessory dwelling unit (ADU) can create flexible space for multigenerational living or guests. The town has specific rules on where ADUs are allowed, how large they can be, and how to permit them. In this guide, you will learn the key lot-size requirements, approvals, and design choices that shape a successful ADU in Dewey-Humboldt. Let’s dive in.
ADU basics in Dewey-Humboldt
Dewey-Humboldt sets its own ADU rules in the town zoning code and reviews building plans under locally adopted building codes. The town enforces setbacks, lot-size minimums, and ADU standards through its permitting process. If you rely on a septic system, Yavapai County’s Environmental Services Unit handles your septic approvals before the town issues building permits. You should check both town and county requirements from the start.
- Town ADU standards are in the zoning code’s ADU section. See the town’s code library for the controlling language in Section 153.075.5. Review the ADU standards in the town code.
- The town’s Administrative Code outlines plan submittal and building code compliance. See the Administrative Code for submittal requirements.
- Septic permits and inspections are handled by the county. Visit Yavapai County Environmental Services.
Minimum lot sizes by zoning
Dewey-Humboldt ties ADU eligibility to parcel size. Verify your zoning and lot area before you design.
- R1 district: minimum parcel size for an ADU is 35,000 sq ft.
- R1L and RMM districts: minimum parcel size is 70,000 sq ft.
- RCU district: ADUs are allowed on lots where the minimum lot size is 87,120 sq ft (2 acres).
These minimums come from Section 153.075.5(A). Check the ADU section of the town code and confirm your zoning on the town’s current map.
ADU size limit
The town caps ADU size using a two-part rule. An ADU shall not exceed 750 sq ft or 25 percent of the primary dwelling’s living area under roof, whichever is greater. Calculate both numbers to see your effective cap, and confirm how the town defines “living area under roof.” You can find this limit in Section 153.075.5(E) of the code. Read the ADU size rule in the town code.
Setbacks, septic, and siting
Your ADU must meet the town’s setback standards for your density district. Many common density classes list front 20 ft, rear 25 ft, and interior side 7 ft as examples, though your exact numbers depend on your district. Always confirm the applicable table in Section 153.069. See the Density Districts section.
If you have a septic system, county setbacks also shape where the ADU can go. Typical county guidance includes 10 ft from structures, 100 ft from a well, 5 ft to a property line next to development, and 50 ft to a property line next to undeveloped land for tanks and leach fields. These distances, plus a required reserve area, often drive the ADU footprint. Review Yavapai County’s septic FAQs.
Occupancy, utilities, and access
The town limits how an ADU can be used. Under Section 153.075.5(H), an ADU must house a non-paying or non-reimbursing relative or guest. Renting the ADU is not authorized in the current ordinance language. See the occupancy rule in the ADU section.
Utilities and access are also specific:
- Electric service: the ADU must be served and metered through the primary dwelling’s electric hookup.
- Driveway: the primary and ADU must share a common driveway or entrance.
- Septic: a separate ADU septic can be approved by the county if needed.
Find these provisions in Section 153.075.5(C) through (D). Review the town’s ADU utility and access requirements.
Permits and timeline
Most ADU projects follow two tracks: county septic approvals and town building and zoning review. Start in the right order to save time.
- Confirm zoning and lot size: verify your parcel’s zoning and density district, then compare to the ADU lot-size minimums. Check the ADU section and zoning references.
- Schedule a septic site investigation if you are not on a public sewer. The county evaluates soil conditions and sets your septic design path. See the county’s site investigation process.
- Prepare your building permit package for the town. Include a site plan, floor plans, elevations, utility details, and septic approvals as required. See the town’s Administrative Code for submittal content.
- Fire authority review: submit required fire protection drawings to the local Authority Having Jurisdiction. Access and defensible-space items may apply. Town Administrative Code, fire and plan review references.
- Inspections and finals: the county inspects septic, the town inspects building systems, and the fire authority inspects as required. Do not occupy until you have final approvals.
County and town review times vary by workload. The county recommends complete applications to speed review. Visit Yavapai County Development Services for process overviews.
Quick project checklist
- Confirm zoning, density district, and lot-size eligibility for an ADU.
- Schedule a septic site investigation or confirm sewer connection.
- Meet with the Town Zoning Administrator or Building Official and Yavapai County Environmental Services.
- Draft a site plan showing the primary home, ADU footprint, shared driveway, septic and well locations, and distances to property lines.
- Prepare plans and engineering for structural, mechanical, plumbing, and electrical.
- Verify electric service capacity since the ADU must use the primary meter.
- Submit the county septic permit and town building permit applications.
- Plan for fire authority review and all required inspections.
Design decisions to make early
Size and layout
Run both ADU size calculations to understand your cap. If 25 percent of your primary living area exceeds 750 sq ft, the larger number controls under the town’s rule. This helps you pick a one-bed, studio, or compact two-bed layout.
Utilities
The ADU will use the primary electric meter. Confirm panel capacity and utility requirements during design. If extra bedrooms or fixtures change the septic design population, the county may require an expanded or alternative system.
Access and parking
The town requires a shared driveway or entrance. Review parking requirements in the zoning code if you plan on-site spaces. Coordinate early if any driveway or access upgrades are needed.
Fire and safety
Expect fire authority input on driveway width, turnarounds, and defensible space. Early coordination with the AHJ helps you avoid rework and delays. See town Administrative Code references to fire review.
Manufactured or tiny homes
If you are considering a manufactured unit or tiny home as an ADU, confirm that it meets town zoning, county septic rules, and state standards. The town’s ADU section controls size, occupancy, and utilities. Review relevant zoning chapters in the code library.
Variances and adjustments
If your lot almost qualifies, Dewey-Humboldt offers two relief paths. Minor percentage changes may be reviewed as administrative adjustments. Larger relief requires a variance through the Board of Adjustment with specific findings. See the town’s adjustment and variance procedures and the Board of Adjustment page.
Buying or selling with ADU potential
If you plan to buy in Dewey-Humboldt with an ADU in mind, focus on lots that meet the town’s minimum parcel sizes and have room for septic setbacks and reserve areas. If you are selling, a clear path to an ADU can be a talking point for multigenerational buyers. Either way, local code and county septic requirements drive feasibility, so confirm details early.
Ready to align your ADU goals with the right property in Dewey-Humboldt? Connect with Paula Stears Thomas for local guidance and a clear next step.
FAQs
What are the minimum lot sizes for an ADU in Dewey-Humboldt?
- R1 needs 35,000 sq ft, R1L and RMM need 70,000 sq ft, and RCU requires a minimum lot size of 87,120 sq ft for ADU eligibility, per Section 153.075.5(A) of the town code.
Can I rent out my ADU in Dewey-Humboldt?
- The town’s ADU section limits occupancy to a non-paying or non-reimbursing relative or guest, so rental use is not authorized under the current ordinance.
How big can my ADU be under town rules?
- The ADU cannot exceed 750 sq ft or 25 percent of the primary living area under roof, whichever is greater, as stated in Section 153.075.5(E).
Do I need a separate septic system for an ADU?
- Not always; the ADU can share utilities, but the county may approve a separate septic if needed and if the site meets design and setback requirements.
Which permits do I need and from whom?
- Yavapai County handles onsite wastewater permits and inspections, while the Town of Dewey-Humboldt reviews zoning, building plans, and issues the building permit.
What if my lot is slightly under the minimum size?
- You may seek an administrative adjustment for minor relief or apply for a variance with the Board of Adjustment, following the town’s application and findings process.
