Southlake council advances changes to Transition Zoning District rules; council adopts modified setbacks and lot-size floor

The Southlake City Council voted 6-0 on April 1 to advance first-reading amendments to the Transition Zoning District (TZD) portion of the city's zoning ordinance, adopting changes that will affect how future transition-district developments calculate density, set lot minimums and protect existing single-family neighborhoods.

Under the amendments approved on first reading, residential density in a TZD will be calculated on the gross area that defines the residential neighborhood boundary and will include neighborhood open space in that calculation. Council adopted a minimum lot area of 10,890 square feet (one quarter acre) for TZD residential lots. The council also added adjacency and screening requirements for nonresidential components of TZD districts that back up to existing single-family districts: nonresidential buildings must meet build-line setbacks of 50 feet for one-story buildings, 70 feet for two-story buildings and 90 feet for three-story buildings measured from the residential boundary. The council also directed that evergreen buffer plantings used for screening must attain eight feet in height within three growth cycles and be maintained in perpetuity.

Stormwater detention areas will not count toward required open-space credit unless the detention area is designed and approved as an aesthetic or passive-recreation amenity for the neighborhood; that determination is subject to staff and council discretion.

Why it matters: The TZD was created as a flexible district to allow mixed residential and nonresidential uses to serve as a transition between higher-intensity corridors and lower-density neighborhoods. Council members and residents said recent TZD proposals raised questions about density calculations, small lot patterns and proximity of nonresidential buildings to existing homes. The ordinance changes set firm minimums and adjacency protections intended to clarify staff and council review of future proposals.

What council discussed: Staff presented a range of options and Planning & Zoning Commission recommendations, including whether to retain a variance provision, how to include or exclude nonresidential area from density calculations, and whether to set a minimum lot area by square footage. Members debated whether the minimum should be expressed as a round 10,000 square feet or a precise quarter-acre measure; council settled on 10,890 sq. ft. Council also discussed whether to forbid three-story nonresidential buildings near neighborhoods; instead the council approved increased build-line distances for each story (50/70/90 feet) and left the three-story maximum as part of the TZD structure but at a greater setback.

Next steps: The ordinance returns for second reading and a public hearing on April 15, 2025. Council directed staff to preserve existing TZD districts under their currently adopted rules and to apply the revised language only prospectively to future TZD applications.

Supporting staff documents cited in council motions included the staff report dated March 25, 2025 and the site-plan review summaries referenced in the ordinance record.