Scottsdale Casita Rules: What Ordinance 4687 Allows

A client called in early 2026 asking about a half-acre lot in the Silverleaf area, the kind with room for a guest house tucked behind a pool. He had read that Arizona legalized backyard rental units and wanted to know how fast he could get a second dwelling built and rented out. The state law he had read about was real. The number he needed, the one that determines whether that project pencils out in Scottsdale specifically, was not in any of the articles he had seen.

That number is 500 square feet, and it is the reason Scottsdale's version of Arizona's ADU reform behaves nothing like the version most casita coverage describes.

One Law, Sold as Uniform

Arizona's accessory dwelling unit reform arrived in two pieces. House Bill 2720, signed in May 2024 and effective January 1, 2025, required any city with a population over 75,000 to permit at least one attached and one detached ADU by right on single-family lots, with rear and side setbacks capped at five feet and no additional parking mandate. House Bill 2928 followed in May 2025, extending a similar framework to unincorporated county land with a compliance deadline of January 1, 2026.

The framing in most coverage treats this as a single statewide unlock. Phoenix, Scottsdale, Mesa, Tempe. Same law, same rights, same math for anyone weighing a casita as a rental play. That framing skips the part that matters most to an investor comparing lots across city lines: the state set a floor, not a ceiling, and Scottsdale built its ordinance right up against that floor in a way that meaningfully changes what a second unit is worth.

What Scottsdale Actually Wrote Into Its Code

Scottsdale did not embrace this reform quietly. City reporting from the fall of 2025 noted that Scottsdale leaders had opposed the legislation over concerns about neighborhood impact and the loss of local control before ultimately amending the zoning ordinance to comply. The Scottsdale City Council adopted Ordinance 4687 on September 30, 2025, and the resulting rules are the most restrictive of any major city in the Valley.

The core provisions, per the city's own ADU page:

1. One attached and one detached ADU are permitted by right on a single-family lot.
2. A third detached ADU is allowed only on lots of one acre or more, and only if one of the units qualifies as affordable housing.
3. The first ADU on a lot follows the state standard: 1,000 square feet or 75 percent of the primary home's floor area, whichever is less.
4. The second and third ADU, if built, are capped at 500 square feet regardless of lot size.
5. No more than six adults, combined, may occupy the main home and any ADUs on the same lot.
6. Electrical and gas utility connections must be separately metered.
7. The lot cannot be subdivided, and no ADU can be sold apart from the main house.

That fourth point is the one that reshapes the investment case. Elsewhere in the Valley, a lot large enough to qualify gets the state's bigger allowance on second units. In Scottsdale, the second casita stays boxed in at 500 square feet no matter how much land surrounds it.

What 500 Square Feet Actually Costs and Rents For

Casita construction in Scottsdale runs roughly $250 to $400 per square foot as of late 2025 pricing. A 500-square-foot second unit at the middle of that range lands around $150,000 to $175,000 before permitting and utility work, and Scottsdale's separate-metering requirement adds several thousand dollars on top of that most other cities in the area don't require. On the rental side, ADU rents in Scottsdale run roughly $1,500 to $2,000 a month for a one-bedroom and $1,900 to $2,600 for a two-bedroom as of mid-2026 market data, so a capped 500-square-foot unit sits at the low end of that range by design, not by market choice.

The Short-Term Rental Rule That Changes the Math

The provision most likely to surprise an investor is the one governing rental use. Scottsdale's ordinance states plainly that "the property owner must reside on the premise for any ADU that is rented" as a vacation or short-term rental, and the same requirement applies if the main home is the one listed short-term while the ADU is occupied long-term. Phoenix, by contrast, had its earlier ban on ADU short-term rentals removed under state preemption and does not carry this owner-occupancy condition.

For a buyer whose plan is pure investment, an absentee owner collecting nightly rates on a casita while renting the main house long-term, Scottsdale's rule closes that door. The unit can still be leased long-term to a separate tenant without the owner living on site. Short-term use is where the requirement kicks in.

Guest House or ADU: Two Categories, One Common Mix-Up

Scottsdale also maintains an older, separate land use category that predates this reform entirely: the Guest House. Per the city's guest house code page, a Guest House is a detached accessory building for the homeowner's own guests. It is explicitly not a dwelling unit, has no kitchen requirement in the same sense, and cannot be rented separately from the main residence under any circumstance. There is no cap on how many guest houses a property can have, but their combined floor area cannot exceed half the main home's gross floor area.

This matters because buyers researching casita potential on a listing sometimes see an existing detached structure labeled a guest house and assume it can be converted into rental income. It cannot, not without a separate ADU permit and compliance with the full Ordinance 4687 requirements, including the metering and occupancy rules above. Confirming which category a structure falls under, before writing an offer contingent on rental income, is worth a call to the city rather than an assumption from a listing description.

One Application, Day One

Here is the number that tells you how this has actually played out. The ordinance took effect on September 30, 2025. By October 1, the very next day, the City of Scottsdale had logged exactly one formal ADU application.

A single day is not a verdict on the whole reform, and the city has certainly processed more applications since. But that opening number lines up with what the rest of the ordinance would predict. A 500-square-foot second-unit cap, mandatory separate metering, a six-adult occupancy limit, and a short-term rental restriction that Phoenix doesn't carry add up to a return that plenty of Scottsdale homeowners are still weighing against the older, simpler guest house route. Two additional layers compound the hesitation for lots in the city's most desirable areas. HOA covenants remain fully enforceable regardless of what the state law permits, and Scottsdale's Environmentally Sensitive Lands Ordinance restricts disturbance of desert washes, native saguaro and ironwood, and hillside slopes over 15 percent, which shrinks the buildable footprint on many North Scottsdale lots before the ADU rules even come into play.

What This Means If You're Evaluating a Scottsdale Lot

If you're comparing a Scottsdale property to something in Phoenix with casita income in mind, the honest starting point is that the same state law produced two different investments. Phoenix allows a larger second unit on bigger lots and dropped its short-term rental restriction. Scottsdale did neither. Before you price a lot's income potential, pull the HOA's CC&Rs, ask whether the parcel carries an ESLO overlay, and confirm with the city whether an existing structure is a Guest House or a permitted ADU. We've walked through the broader investment math for Valley properties in our guide to getting started with Phoenix investment properties, and if new construction is part of the plan, our piece on evaluating new construction opportunities in Scottsdale covers the site-specific questions worth asking before you commit.

Quick FAQ

Can I rent a Scottsdale casita on Airbnb without living on the property? No. Scottsdale requires the owner to reside on site for any ADU or main home used as a short-term or vacation rental. Long-term leases don't carry this requirement.

Does Arizona's ADU law override my HOA's rules? No. Both HB 2720 and HB 2928 preserve the enforceability of private HOA covenants. If your community's CC&Rs restrict accessory structures, that restriction stands regardless of city zoning.

Is a guest house the same thing as an ADU in Scottsdale? No. A Guest House cannot be rented separately from the main home and isn't classified as a dwelling unit. An ADU can be leased to a separate tenant but must meet the full requirements of Ordinance 4687, including separate metering and the occupancy cap.

Zoning details like these are exactly where a banking and economics background earns its keep, reading the fine print before it becomes an expensive surprise. If you're weighing a Scottsdale property against other options in the Valley, or want a second read on what a specific lot's ADU potential is actually worth, Rami Haddad is glad to walk through the numbers with you.