Do I need an architect to build a custom home in Arizona?

You do not always need an architect to build a custom home in Arizona. State law sets a size line. Under A.R.S. 32-144, a person who is not a registered architect can legally design a one or two story building up to 3,000 square feet without an architect's stamp, as long as it holds no more than 20 people and its longest structural span stays under 20 feet. Above that size, or with a more complex design, you usually need a registered architect or a registered engineer to prepare and seal the plans. Either way, your city or county building department still requires complete, code-compliant drawings before it issues a permit.

The 3,000 square foot rule that decides it

The line between needing a registered design professional and not needing one is 3,000 square feet of floor area. A.R.S. 32-144 exempts "a nonregistrant who designs a one or two story building or structure in which the square footage of the floor area measured to the outside surface of the exterior walls does not exceed three thousand square feet, that is not intended for occupancy by more than twenty persons on a continuous basis and in which the maximum span of any structural member does not exceed twenty feet."

A nonregistrant is anyone who is not a registered architect or engineer. That can be a homeowner, a draftsperson, a designer, or a builder's in-house design team. The Arizona State Board of Technical Registration enforces these rules and registers the architects and engineers who fall under them.

The 20-foot span limit has a built-in exception. You can exceed it if the long span uses wood or steel roof or floor trusses, or lintels, approved by a registered engineer. So a wide open great room is still possible under the exemption, as long as an engineer signs off on the members that carry the load.

When your custom home will need an architect or engineer

Most true custom homes in the Scottsdale and Phoenix market run larger than 3,000 square feet, which puts them outside the exemption and into stamped-plan territory. The median new custom home in this metro is commonly built in the 3,000 to 5,000 square foot range, and homes on view lots in Rio Verde or north Scottsdale often go larger. Once you pass 3,000 square feet, a registered architect or engineer must design the home or stamp the plans.

A few design choices push you toward a stamped plan even on a smaller footprint:

• Three or more stories. The exemption covers one or two story buildings only. A three-story home needs a registered design professional.
• Long open spans without engineered members. A span over 20 feet that does not use engineer-approved trusses or lintels falls outside the exemption.
• Complex structure or unusual loads. Steep hillside lots, deep basements, heavy roof loads, or post-tension slabs on Arizona's expansive soils usually call for an engineer's analysis and seal.

Even when state law lets a nonregistrant design the home, the building department can still require an engineer's stamp on the structural or foundation plans. Phoenix-area soils swell and shrink with moisture, so foundation engineering is common even on modest homes.

What the building department requires either way

Your building department requires a complete, code-compliant plan set before it issues a permit, whether or not an architect drew it. In unincorporated Maricopa County, plans are reviewed against the 2018 International Residential Code (IRC), adopted by the county in 2022, plus the 2018 plumbing, mechanical, and electrical codes. Cities such as Scottsdale and Phoenix run their own permit offices and adopt their own code editions, so confirm the standard with the office that covers your lot.

A residential permit submittal usually includes a site plan, floor plans, elevations, foundation and framing details, an energy compliance form, and the structural calculations that back up the design. The reviewer checks that everything meets code and the adopted edition. Incomplete or non-code drawings get kicked back with corrections, which adds weeks. A clean, professional plan set is the single biggest factor in a fast permit.

This is where a designer or architect earns the fee even on an exempt-size home. They know what each reviewer expects. They know how to draw it so it passes the first time. The cost of a redraw and a second review round often equals what a professional would have charged up front.

A quick word on what a "stamp" really means. When an architect or engineer seals a plan, they take legal responsibility for it. They are saying the design meets code and is safe to build. That seal is what lets the building department approve a home that falls outside the nonregistrant exemption. It is not a formality. It is a licensed professional putting their name on the safety of your home, which is why the law requires it once a home gets large or complex.

The energy code is another reason plans get technical. Arizona homes have to meet insulation, window, and HVAC efficiency rules. A designer who knows the local energy form can fill it out right the first time. Get that wrong and the permit stalls, even when the rest of the plan is clean.

Architect, home designer, or builder: which makes sense

The right choice depends on your home's size and how custom you want it, not on a one-size rule. A registered architect brings full design service, code knowledge, and a stamp that satisfies any size or complexity. Architect fees commonly run 8 to 15 percent of construction cost, so on a 600,000 dollar build that is roughly 48,000 to 90,000 dollars.

A residential home designer costs less and works well for straightforward plans within or near the exemption size. Many designers pair with a registered engineer for the structural stamp, which keeps total design cost down while still satisfying the building department. This is a common path for homes in the 2,500 to 4,000 square foot range.

A design-build builder like Jematell Homes folds design and construction into one team. You get plans drawn to build cleanly, with an engineer brought in for the structural seal when the size or design calls for it. That keeps the design honest to your budget, since the people drawing it also have to build it.

Here is a simple way to decide. Picture your finished home. Is it one or two stories? Is it under 3,000 square feet? Is the structure straightforward? If you answer yes to all three, the law may let a designer handle it. If you answer no to any of them, plan for a registered architect or engineer.

If your home is under 3,000 square feet, simple in structure, and one or two stories, you may not need an architect at all. If it is larger, taller, or structurally ambitious, plan for a registered architect or engineer. Confirm the stamp requirements with your building department before design starts, since a single city amendment can change what they want on the plans.

The Jematell Homes approach

We run the land due diligence before you commit to a lot. We would rather answer your questions before you build than after, so get in touch any time.

Sources

• A.R.S. 32-144 (Exemptions and limitations; nonregistrant design)
• Maricopa County Residential Construction permits
• Maricopa County Adopted Regulations (2018 building codes)
• Arizona State Board of Technical Registration (architect applicants)