Building a casita in Scottsdale: the rules, fees and the math

The rules in Scottsdale

Separately metered electric, gas, water and sewer are required unless the utility determines otherwise, and the unit's address must be displayed at its entrance. Each unit needs private outdoor living space at least 5 ft deep and 50 sq ft. Existing guest houses are not grandfathered as ADUs. The 2025 state amendment shrank the airport exclusion zones around Sky Harbor and Scottsdale Airport, so more lots qualify. The city reported only one formal ADU application as of September 2025.

Source: City of Scottsdale: Accessory Dwelling Units; scottsdaleaz.gov; eservices.scottsdaleaz.gov; ww2.scottsdaleaz.gov; ww2.scottsdaleaz.gov. Read October 7, 2026.

Fees in Scottsdale

• Permit and plan review. Single-family permit fee schedule effective July 1, 2024: a base fee plus per-square-foot charges for livable and covered area.
• Utility connection and capacity. Scottsdale requires separately metered utilities for a unit unless the utility decides otherwise, which triggers water and wastewater development fees: $5,003 water plus $2,696 wastewater for a 5/8- to 1-inch meter, $7,699 together (schedule dated August 2023).

In June 2026 the state capped the development (impact) fees a city may charge an ADU for services other than water and sewer at the lesser of 25% of the single-family fee or the unit's proportionate share, and limited water and sewer fees to the unit's added demand (HB 2946, signed June 5, 2026). Most cities had not yet re-published schedules when we read them; Glendale's 25% ADU line is the first we found. Expect ADU impact fees to fall toward that cap. Governor's announcement.

What the state law guarantees here

Whatever the local code says, in Scottsdale these points come from A.R.S. § 9-461.18 and the city cannot be stricter:

• At least one attached and one detached ADU on any lot with a single-family home, as a permitted use (no public hearing, no variance)
• A unit up to 75% of the main home's gross floor area or 1,000 sq ft, whichever is smaller (cities may allow larger)
• A third, detached unit on lots of one acre or more if one unit is deed-restricted affordable
• Separate long-term rental of either the house or the ADU (leases of 90 days or more, or month to month)

The math in Scottsdale

Redfin's median sale price in Scottsdale is $419 per square foot. A new casita builds for about $265 to $280 per finished foot and a garage conversion for about $120. That puts Scottsdale in the "Clears even at a discounted appraisal" tier: one square foot of new casita, at the typical $272 build cost, comes out +$42 at a 75% appraiser credit and +$147 at full credit. A conversion clears at either credit.

The target areas page explains the tiers and the math page has the calculator. Rent is the other half: see rental math.

Owners and investors in Scottsdale

• Homeowners get a by-right unit for family, guests or long-term rent, with the same appraisal and lender rules as anywhere in the Valley.
• Investors can treat the casita as the piece that moves a house out of its neighborhood's price band at resale, as our two Maryvale sales show on the case studies, and as monthly income in the meantime. Scottsdale's rental rules above say whether both units can be let separately.
• Either way the lot decides: setbacks, utilities, sewer depth and easements. Request a property review and we confirm the current Scottsdale rules for your address.

Other city pages: Phoenix, Mesa, Chandler, Gilbert, Tempe, Glendale, Peoria, Surprise, Goodyear, Buckeye.