Residential drafting in Flagstaff, Arizona
Flagstaff sits at around 7,000 feet, and that governs the drawings more than anything else on this page. Snow load, freeze depth, ice, roof drainage, and protected plumbing are the central design questions, and a set drawn for the valley does not transfer.
The housing runs from historic railroad, downtown, Southside, and Route 66 fabric through postwar houses, mountain cabins, student oriented infill, and newer subdivisions. Older wood frame houses may have crawlspaces, stone or early concrete foundations, steep roofs, enclosed porches, and layered additions. Cabin and mountain house forms often have irregular framing, lofts, wood stoves, and site built roof systems that have to be verified in the field rather than assumed.
Ponderosa pine lots bring wildland urban interface detailing, defensible space, roof and vent protection, and construction access planning. Post fire flooding is a real local risk, and a parcel nowhere near a creek can still take runoff from an upstream burn scar.
One planning item that gets missed: snow storage. Plowed snow has to go somewhere, and it cannot end up blocking the accessory unit's path, its parking, fire access, or drainage. That gets drawn, not assumed.
ADU standards
Setback, size, and parking rules for an accessory dwelling unit in Flagstaff.
| Maximum size | 75 percent of the house or 1,000 sq ft, whichever is less (Table 10-40.60.030.A(9)) |
|---|---|
| Minimum allowance | Up to 800 sq ft is allowed regardless of how small the house is (Table 10-40.60.030.A(9)) |
| Rear and interior side setback | 5 ft minimum (Table 10-40.60.030.A(3)(a)) |
| Height | The zoning district maximum. No reduction tied to the setback (Table 10-40.60.030.A) |
| How many | One detached and one attached or interior. One more detached on a lot of an acre or more with a Category 1 permanently affordable unit (Table 10-40.60.030.A(4)) |
| Rented separately | Permitted as long term rental housing (Table 10-40.60.030.A(8)) |
Flagstaff is above the state population threshold, though only just, so state law applies here and does not apply in Prescott or Sedona.
The size rule has a floor most cities do not offer. The ordinary cap is 75 percent of the house or 1,000 square feet, whichever is less, but a unit of up to 800 square feet is allowed regardless of how small the house is (Table 10-40.60.030.A(9)). On a small older house that is the difference between a studio and a real dwelling.
A detached accessory structure built before February 2016 that already sits inside the setbacks can be converted to a dwelling, provided nothing is added outside and the height does not increase within the setback.
The city runs a model plans library with a dozen designs. A model plan is a head start on the building. It is not a site plan, and it does not resolve snow storage, grade, trees, fire access, or your setbacks.
Planning office: Flagstaff Planning and Development Services
Sources: Flagstaff Zoning Code 10-40.60.030. Ordinance 2025-26, adopted December 2025. A.R.S. 9-461.18. Last checked August 2026.
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