ADU rules in McAllen

McAllen's new Unified Development Code (adopted February 9, 2026) lists Accessory Dwelling Unit as a use permitted by right in every residential base district (A-O, R-1, R-2, R-3), the M-1 Local Mixed Use district, and both City Core subdistricts (DT and UT). Table 3.3.5-1 expressly allows the detached type where the primary use is a detached single-family dwelling, with no minimum lot size. A detached ADU must be placed in the rear of the lot and meet district setbacks and height rules; only one ADU is allowed per lot.

The UDC defines an ADU as a unit either integrated within a single-family dwelling or located in a detached accessory building, and Table 3.3.5-1 allows the attached types (to the primary dwelling, or above a garage) on single-family lots. On townhouse lots only the above-garage type is allowed; on duplex through multiplex lots the attached-to-primary type is not allowed but detached and above-garage are. The same permitted-by-right districts apply as for detached units.

Two general limits still apply everywhere: the ADU cannot exceed the height or size of the primary dwelling, and a detached accessory building is normally limited to 50 percent of the principal structure's floor area unless the Planning Director authorizes more, which can bind even where Table 3.3.5-1 states no maximum. General accessory rules add an 18 ft height cap (25 ft above a detached garage), 5 ft side and 10 ft rear setbacks, and 5 ft separation from the principal building.

The property owner must occupy the principal dwelling or the Accessory Dwelling Unit as their permanent residence. This is a flat requirement of the ADU section with no stated exceptions; the other unit can then be occupied by someone else.

The use table's Minimum Parking Ratios column lists 1/DU for the Accessory Dwelling Unit row, and §4.4.3.D makes those table ratios the governing off-street minimums. Uptown (UT) projects can take a 50 percent reduction, M-1 and M-2 projects 25 percent, and infill development 30 percent with Planning Director approval. Primary-dwelling parking is separate.

In every district where ADUs are allowed (A-O, R-1, R-2, R-3, M-1, DT, UT) the use table shows 'P', permitted by right subject to the §3.3.5.A standards; no district requires a conditional use permit for an ADU. Blank cells (C-1, C-2, I-1, I-2, M-2) mean the use is not allowed there at all. Standard building permits through the Development Center still apply.

The UDC does not prohibit renting out the ADU (or the main house) long term, as long as the owner permanently occupies one of the two units and the ADU shares utility connections with the primary dwelling. The Chapter 46 STR article expressly covers accessory buildings and requires a 24/7 local contact able to respond within one hour and smoke detectors; it ties STR status to owner-occupied contexts and excludes non-owner-occupied multi-unit operations from the STR category.