ADU rules in Meridian

A detached backyard ADU is an accessory use of right in every Meridian residential district (R-2, R-4, R-8, R-15, R-40) under Table 11-2A-2 and in all three traditional neighborhood districts (O-T, TN-C, TN-R) under Table 11-2D-2, subject to the specific use standards in UDC 11-4-3-12. Ordinance 25-2102, adopted and effective 11-18-2025, renamed that section 'Dwelling, accessory' and allows the unit inside the house, attached to it, or in a detached structure, including above, beside, or within a garage; a detached ADU must sit to the side or rear of the primary dwelling. Only one ADU is allowed per property, and it must be a building on a foundation (vehicles and tents are barred, and the prior express ban on manufactured and mobile homes was replaced by the foundation requirement). The ADU is an ordinary building for dimensional purposes: it must meet the district setbacks (for example 15 feet rear and 5 feet interior side in R-4) and the district height cap (35 feet in R-2, R-4 and R-8; 40 feet in R-15; 60 feet in R-40).

The same section allows the ADU 'within or attached to the primary dwelling', so a basement or internal conversion and an addition are treated exactly like a detached cottage; the one-per-property limit covers both forms, so a homeowner picks one. UDC 11-4-3-12(H), added by Ord. 25-2102, requires that both the primary unit and the ADU each have at least one exterior egress door and that no openings connect them, which means an internal conversion has to be fully separated from the house. The 900 square foot or 50 percent size cap and the two-bedroom limit apply to internal and attached units as well as detached ones. Attached and internal ADUs run through the same building-permit path, with no zoning certificate and no hearing.

UDC 11-4-3-12(E) caps an accessory dwelling unit at nine hundred square feet or fifty percent of the primary dwelling, whichever is less, and at no more than two bedrooms. On a 1,500 square foot house the binding figure is 750 square feet, not 900. There is no separate ADU height cap: the district maximum building height applies (35 feet in R-2, R-4 and R-8; 40 feet in R-15; 60 feet in R-40), and Ord. 26-2119 of 3-17-2026 clarified that residential structures may not exceed the district maximum. This cap now sits below the Idaho floor: Idaho Code 67-6541(2)(d), effective 7-1-2026, requires covered cities to prohibit limiting an ADU to less than 1,000 square feet or 75 percent of the primary dwelling, and Meridian must amend its code to comply by February 1, 2027, so expect this number to rise.

Meridian repealed its owner-occupancy rule on 11-18-2025. Ordinance 25-2102 struck the former UDC 11-4-3-12(B), which had required the property owner to 'reside on the property for more than six (6) months in any twelve-month period' and to prove owner occupancy by title records, vehicle registration or voter registration. What replaced it is an ownership check, not an occupancy rule: ownership of the primary dwelling is confirmed through Ada County records, and the ADU may not be subdivided or otherwise segregated in ownership from the primary dwelling, so the two units cannot be sold separately. Idaho Code 67-6541(2)(e) independently bars owner-occupancy requirements in covered cities and must be reflected in local law by February 1, 2027, so the repeal is now also locked in by state law. Beware of stale text: Municode's codified section still displays the repealed six-month rule because the library is codified only through Ord. 25-2099 of 9-23-2025.

UDC 11-4-3-12(G) sends a property with an ADU to Table 11-3C-6 'for single-family dwellings, as determined by the total number of bedrooms on the property'. That table requires 2 spaces (at least 1 in an enclosed garage) for 1 to 2 bedrooms, 4 spaces (at least 2 enclosed) for 3 to 4 bedrooms, and 6 spaces (at least 3 enclosed) for 5 or more, so adding a 2-bedroom ADU to a 3-bedroom house pushes the property from 4 required spaces to 6. Converting a garage or carport into an ADU is not allowed unless the required parking can be provided elsewhere on site, and all required spaces must be on the same lot. Idaho Code 67-6541(2)(b), effective 7-1-2026, requires covered cities to 'Prohibit requiring any off-street parking or guest parking for any accessory dwelling unit unless the principal dwelling unit does not have off-street parking or the street is not paved and designed or constructed for on-street parking or unless the principal dwelling unit is within one-fourth (1/4) mile of transit, an employment area, or commercial services', a change Meridian must make by February 1, 2027; note the transit clause runs toward allowing parking requirements near transit, not waiving them.

An ADU is reviewed administratively with no public hearing. Table 11-2A-2 lists the use as an accessory ('A') use in all five residential districts, and UDC 11-2A-2(A)(1) states that secondary dwellings 'shall be reviewed in accord with the standards established in title 10 of this Code and shall not require certificate of zoning compliance and/or accessory use approval', so there is no zoning certificate and no accessory use permit. Ordinance 25-2102 added UDC 11-4-3-12(C), which requires city permitting approval before building, placing or maintaining an ADU; in practice that is a residential building permit filed through the Citizen Access portal against the Building Division's ADU submittal checklist. No conditional use permit is involved anywhere in the residential or traditional neighborhood districts. Idaho Code 67-6541(3), effective 7-1-2026, now also requires conforming ADU projects to be approved administratively and as a matter of right, which matches Meridian's existing process.

Nothing in UDC 11-4-3-12 restricts renting an ADU, and the owner-occupancy condition that used to sit on the use was repealed on 11-18-2025, so a Meridian owner may rent out the ADU, the main house, or both. The unit may not be subdivided or segregated in ownership from the primary dwelling, so it cannot be sold as a separate property. Meridian has no short-term-rental chapter in its city code and the City Clerk's license list has no short-term-rental license; Idaho Code 67-6539, rewritten by 2026 ch. 22 effective 7-1-2026, forbids any city ordinance that prohibits any type of short-term rental and provides that no city 'shall require a license, fee, permit, certification, or registration to operate a short-term rental', so an ADU can be used as a short-term rental subject only to generally applicable noise, parking, nuisance and traffic rules. One local limit does bite occupancy: UDC 11-4-3-12(K) caps the combined occupants of both units at Meridian's 'family' definition, which allows a group of not more than ten persons who need not be related.