ADU rules in Grapevine

Grapevine allows a detached accessory dwelling unit, but only in the R-20 Single-Family District (20,000 sq ft minimum lots), where it is a listed permitted secondary use with standards in Section 42.C.6. The more common R-12.5, R-7.5, and R-5.0 districts do not list ADUs and each limits the lot to one single-family detached dwelling, so most Grapevine homeowners cannot build one. Where allowed, the ADU must be a site-built structure in the rear yard behind the primary home; modular and manufactured units are prohibited.

The ADU standards make an attached or internal secondary unit impossible: the unit must sit in the rear yard behind the primary dwelling and keep a minimum 10 ft separation from it, so every Grapevine ADU is detached by rule. A building with two attached dwellings is a duplex, a separate use confined to the R-3.5 Two-Family District, not something permitted on a single-family lot.

General secondary-structure rules stack on top of the ADU caps: no more than two secondary structures per lot with cumulative size limits by lot size (1,500 sq ft cumulative on lots of 20,000 sq ft and larger, the R-20 minimum), and exceeding 1,500 sq ft cumulative or 16 ft height on such lots requires a conditional use permit. Setbacks are 15 ft side and 25 ft rear on internal lots, larger on corner and reverse-frontage lots, plus 10 ft from the primary dwelling.

Neither the ADU standards in Section 42.C.6 nor the R-20 secondary use list contains an owner-occupancy requirement for either unit. The code instead removes the rental use entirely: secondary uses may not be a source of income to the owner or user of the principal dwelling, and the ADU cannot be leased separately, so the unit functions as extra living space for the household rather than a landlord product.

Section 42.C.6.d requires one space for the ADU behind the front building line of the primary structure, in addition to the normal single-family requirement, which Section 56.C sets at 2 spaces per dwelling unit. Driveway access and off-street parking must be shared with the primary dwelling; a second detached driveway for the ADU is not allowed.

In the R-20 district an accessory dwelling unit is a listed permitted secondary use, so a code-compliant ADU needs only standard building permits, not a conditional use permit or public hearing. A CUP enters the picture only to exceed the general secondary-structure limits (1,500 sq ft cumulative size or 16 ft height). Outside R-20 there is no permit path at all because the use is not listed in any other residential district.

Both the Section 12 definition and Section 42.C.6.a bar renting the ADU separate and apart from the primary dwelling, and the R-20 secondary-use chapeau bars secondary uses from being a source of income, so a Grapevine ADU is family or guest space, not a rental unit. Section 21 prohibits all single-family short-term rentals citywide (STRs are allowed only in large R-MF and RMF-2 complexes with a CUP). Utility service must share the primary home's meter, reinforcing that the unit is not independently occupiable for rent.