Most Phoenix Casita Guides Quote 1,000 Sq Ft. Section 706 Has Two Tiers.
Service Area: Phoenix, AZ
Almost every Phoenix casita guide quotes a 1,000 square foot cap and stops there. That number only applies to lots up to 10,000 square feet. Cross that line and Phoenix Zoning Ordinance Section 706 puts you on a second tier: the lesser of 3,000 square feet or 10% of net lot area. On a 12,000 square foot lot, that is a 1,200 square foot casita. Which tier your lot falls into is the first thing we check.
Apex Drafting is an Arizona business. We draft from Colorado City, Arizona, to Arizona code, and we work with Phoenix homeowners, builders, and contractors remotely: video calls, shared plan review, and permit-ready sets delivered digitally. Some of the firms competing for Phoenix drafting searches operate from outside the state. We do not.
Phoenix casita size limits live in Zoning Ordinance Section 706
Phoenix rewrote its accessory dwelling unit rules to comply with state law, and the operative text sits in Phoenix Zoning Ordinance Section 706. The size limit is what drives a drawing set, and Section 706 does not use one number. It uses two tiers keyed to lot size.
| Lot size | Maximum ADU size under Section 706 |
|---|---|
| Up to 10,000 sq ft | The lesser of 1,000 sq ft or 75% of the primary dwelling's gross floor area |
| Over 10,000 sq ft | The lesser of 3,000 sq ft or 10% of net lot area |
What the two tiers mean on a real lot
On an 8,000 square foot lot with a 1,200 square foot house, 75% of the primary dwelling is 900 square feet. The percentage binds before the flat cap does, so the answer is 900, not 1,000.
On a 12,000 square foot lot, the second tier applies. Ten percent of net lot area is 1,200 square feet, well under the 3,000 square foot ceiling, so 1,200 is the cap. That is a two-bedroom casita, not a studio. Pages quoting a flat 1,000 square feet understate what a larger Phoenix lot can carry.
On a one acre parcel, 10% of net lot area is roughly 4,356 square feet, so the 3,000 square foot ceiling is what actually limits you. A 3,000 square foot accessory dwelling is a full house, and it has to be drafted like one: full structural, full mechanical, and a site plan resolving utilities, drainage, and access. On a small lot the percentage of the primary dwelling decides the cap; on a large lot the percentage of the lot does.
Setbacks, parking, height, and owner occupancy
Section 706 sets a 5 foot minimum side and rear setback. There is no ADU-specific off-street parking requirement, which frees up square footage on tight infill lots that would otherwise go to a parking pad. Height follows the underlying zoning district rather than a separate ADU standard, so the zoning designation on your parcel governs.
Owner occupancy is not required to rent an ADU for 90 days or longer. Short-term rental is different: for ADUs built after September 14, 2024, the owner must be on the premises. If your financial plan depends on nightly rental, settle that before design starts.
HB 2720 is the state law behind the change
HB 2720 was signed May 21, 2024 and took effect January 1, 2025. It requires every Arizona municipality over 75,000 residents to allow accessory dwelling units on any lot where single-family housing is allowed, and sets a statewide floor of at least one attached and one detached ADU per single-family lot.
The provision with the most practical bite is procedural: cities may no longer require a special use permit, variance, or public hearing for a conforming ADU. Before, a conforming casita could still die at a hearing. Now the path is an administrative plan check, which means the quality of the submittal sets your timeline.
Phoenix metro cities covered by the law include Phoenix, Mesa, Chandler, Gilbert, Scottsdale, Glendale, Tempe, Peoria, Surprise, Goodyear, and Avondale. Each implements the state floor through its own ordinance, so the current per-lot count in Phoenix is something we confirm against the live text of Section 706 at the start of every project rather than from a summary.
The acre-plus third unit almost nobody mentions
HB 2720 carries a provision missing from essentially every Phoenix casita guide we reviewed. On lots of one acre or larger, a municipality must allow one additional detached ADU, provided at least one of the units on the lot is a restricted-affordable dwelling unit occupied by a household at or below 80% of area median income.
That maps onto acre-plus parcels in Cave Creek, Desert Hills, New River, North Scottsdale, and unincorporated Maricopa County. Stack it on the large-lot size tier and one acre can support a primary residence plus detached accessory units drawn to a 3,000 square foot ceiling. That is a small multi-building site, and the affordability restriction has to be designed in from the beginning.
HB 2928 carried the same rights into the counties
HB 2928 was signed May 23, 2025 and extended ADU requirements to Arizona counties, with a compliance deadline of January 1, 2026. Homeowners in unincorporated Maricopa County now hold ADU rights comparable to those inside Phoenix or Mesa, including the acre-plus provision. County parcels tend to be larger, so the large-lot math applies more often out there, and the highest-value drafting work in the metro often sits on those parcels.
The Phoenix market these drawings get built in
Phoenix-Mesa-Chandler is the 10th most populous metropolitan area in the United States, at 5,228,938 residents as of July 1, 2025. It added 59,065 people in the year to July 2025, a gain of 1.14% and the 4th-largest numeric increase of any US metro. Growth cooled from 1.62% the prior year, but a metro adding nearly 60,000 residents while decelerating is still one of the busiest construction markets in the country. Maricopa County holds 4,689,558 people, the City of Phoenix 1,665,481.
Permits track it. Single-family permits rose 39% in Maricopa County and 43% in Pinal County during the 2024 surge, with 18,498 single-family permits pulled across the two counties in the first seven months of that year alone. Phoenix issues roughly 44.7 building permits per 1,000 residents, among the highest development volumes of any US city. Review counters at that volume are unforgiving of incomplete submittals.
On values: Phoenix REALTORS put the metro median at $480,000 at the 2025 close, up 0.3% year over year, with days on market at 75, up 15.4%. The City of Phoenix median was $485,000, and Zillow's average home value for the city reads $410,222, down 2.1% year over year. Flat prices plus listings sitting longer pushes owners to add square footage to what they already own instead of trading up, which is why casitas, additions, and garage conversions are the strongest work here.
Submarkets, keyed to lot size rather than name
Arcadia and Paradise Valley. Lots here commonly clear the 10,000 square foot threshold, which puts them on the larger Section 706 tier. Nearby Scottsdale carries a $1.2 million median, and at that price the brief is usually a guest house built to match the main residence.
North Phoenix. Acre-plus parcels are common enough that the third-ADU provision is a live option rather than a footnote. This is where the 10%-of-net-lot-area math and the affordability restriction get worked out together on one site plan.
Ahwatukee. Predominantly 1980s and 1990s housing stock, with garages sized for that era and floor plans that no longer match how families live. Garage conversions and rear additions dominate, and both need accurate as-builts first.
Downtown Phoenix. Small infill lots, so the 1,000 square foot cap and the 75% test both bind. It is also where the absence of a parking requirement matters most, because a required pad can erase the buildable area on a narrow lot.
Mesa. Mesa adopted Ordinance 5883 on October 7, 2024, allowing ADUs on any lot with a single residence, with a 75% or 1,000 square foot cap, 5 foot rear and side setbacks, and a waived covered-parking replacement requirement for garage conversions. That last item is what makes Mesa garage conversions pencil. Mesa has no city plan library, so its homeowners are told to budget $3,000 to $15,000 for custom architectural plans.
The rest of the metro. Goodyear ($475,000), Surprise ($430,000), Avondale ($418,000), Gilbert ($595,000), and Queen Creek ($655,400) are the price points where an accessory unit changes a household's economics most directly.
What Phoenix casitas actually get built for
Roughly 60% of casita buyers here build to house family members and roughly 40% build for rental income, with typical casitas landing between 400 and 800 square feet. That split drives the design: a unit for an aging parent needs a zero-step entry, wider doors, and a bathroom laid out for mobility aids, while a rental needs sound separation, a metering strategy, and its own entrance. See multigenerational and universal design.
Working on a Phoenix, AZ project right now?
Send us the lot and what you want to build. We'll confirm which local rules apply to your parcel and come back with a firm number, at no cost.
The drafting work Phoenix projects need most
ADU and Casita Plans
Drawn against the Section 706 tier your lot actually falls into, with setbacks, height, and occupancy resolved before the design is fixed.
ADU Plans and DesignCustom House Plans
For lots where a standard footprint does not fit: slope, an irregular parcel, or a large-lot ADU drawn to the 3,000 square foot ceiling.
Custom House PlansStock House Plans from $799
The fast path for a standard lot, and unlike a free pre-approved city plan, a stock set from us is meant to be modified for your site.
Stock House PlansThe Phoenix mix also runs to home additions and remodel drafting, permit-ready drawings and as-builts for garage conversions, energy-efficient design for a climate where cooling load drives the envelope, and 3D renderings. See all services and pricing.
Phoenix's free plan library, and where a $799 stock plan fits
Phoenix is building toward offering approved standard ADU plans at no cost, following an ADU design competition with winners announced December 3, 2024 and entries capped at 1,000 square feet. The constraint is what decides whether it works for you: approved plans must be submitted as-is, and any modification requires a new submittal outside the streamlined process. That is fine if your lot, utilities, slope, and household match the standard plan exactly. It stops being fine the moment you need a different bedroom count, a different orientation, or a footprint that reflects the larger Section 706 tier your lot qualifies for.
Tucson already runs a working version, a Casita Model Plan Library with nine pre-approved plans, so the concept is proven in Arizona. Our position is simple: a $799 stock plan is the modifiable middle between a free but frozen city plan and a fully custom set at $3,000 to $15,000.
Phoenix casita and drafting questions we hear most
Does Arizona law give me the right to build a casita in Phoenix?
Largely, yes. HB 2720 was signed May 21, 2024 and took effect January 1, 2025. It requires every Arizona municipality over 75,000 residents to allow accessory dwelling units on any lot where single-family housing is allowed, and sets a statewide floor of at least one attached and one detached ADU per single-family lot. It also removed the special use permit, variance, and public hearing requirement for a conforming ADU. Cities write their own implementing ordinances, so we confirm the current per-lot count against Phoenix Zoning Ordinance Section 706 for every project.
How big can a casita be on my Phoenix lot?
Phoenix Zoning Ordinance Section 706 uses two tiers keyed to lot size. On lots up to 10,000 square feet, the maximum is the lesser of 1,000 square feet or 75% of the primary dwelling's gross floor area. On lots over 10,000 square feet, it is the lesser of 3,000 square feet or 10% of net lot area. That second tier is why a 12,000 square foot lot can carry a 1,200 square foot casita. Most guides quote only the 1,000 square foot number, which is wrong for anyone on a larger lot.
I own an acre or more. Can I build a third unit?
HB 2720 includes a provision most Phoenix guides omit. On lots of one acre or larger, a municipality must allow one additional detached ADU, provided at least one of the units is a restricted-affordable dwelling unit occupied by a household at or below 80% of area median income. That matters on acre-plus parcels in Cave Creek, Desert Hills, New River, North Scottsdale, and unincorporated Maricopa County, and the restriction has to shape the site plan from the first sketch.
My property is in unincorporated Maricopa County. Do the ADU rules reach me?
Yes. HB 2928, signed May 23, 2025, extended ADU requirements to Arizona counties with a compliance deadline of January 1, 2026. Homeowners in unincorporated Maricopa County now hold ADU rights comparable to those inside city limits, including the acre-plus provision. County parcels tend to be larger, so the large-lot size math applies more often out there.
Phoenix plans to offer free approved ADU plans. Why would I pay for a plan set?
Because free plans come frozen. Phoenix ran an ADU design competition with winners announced December 3, 2024, entries capped at 1,000 square feet, and the city intends to offer approved standard plans at no cost. The catch is that those plans must be submitted as-is: any modification requires a new submittal outside the streamlined process. Our stock plans start at $799 and are built to be modified, which puts them between a frozen city plan and a fully custom set at $3,000 to $15,000.
Can Apex Drafting handle a Phoenix project if you are not sitting in Phoenix?
Yes, and we are an Arizona business drafting to Arizona code. Apex Drafting works out of Colorado City, Arizona. We have no Phoenix office and will not claim one, but several firms competing for Phoenix drafting searches operate from outside the state entirely. Drafting is remote by design: video calls, shared plan review, and permit-ready sets delivered digitally.
Arizona service areas
Phoenix is our covered Arizona metro. The Arizona service area hub covers HB 2720 and HB 2928 statewide, including unincorporated county territory.
Get a Free Quote for Your Phoenix, AZ Project
Tell us what you're building and we'll scope it, confirm the timeline, and give you a firm number before any drafting starts. Every plan set is drafted to your local jurisdiction's documentation standards.
Prefer to talk it through? Call (435) 990-3556.
Ready to start your Phoenix project?
Tell us your lot size and what you want to build. We will identify which Section 706 tier applies and send back a free quote.