Planning staff outline zoning changes, two new residential districts and affordability bonus in housing study

Greg Claxton, a planner with the planning department, presented an update to the Planning Commission on the housing and infrastructure study that would change single‑family bulk standards, simplify duplex rules, allow detached accessory dwelling units (ADUs) in some circumstances, introduce two new residential districts and calibrate a state‑enabled rental affordability bonus.

The study, Claxton said, is intended to balance housing production and neighborhood character and to produce recommendations for the commission in June. "The workshops, I think, have been, a good opportunity for members of the public to kinda come out and talk to us in a fair amount of detail," he said, describing recent public exercises on scale and form.

Staff framed the proposed changes in several clusters. For R and RS (one‑ and two‑family) districts they are considering lowering measured heights to about 2½ stories in many locations, clarifying how height is measured (for example whether exposed basements count), and including eave and roofline measurements to encourage pitched roofs. Claxton said the current Urban zoning overlay allows three stories within 45 feet but an exposed basement can effectively add about 7 feet, potentially producing a 52‑foot building in some calculations; staff would like to reduce those extremes to better match existing neighborhood form.

On unit types, staff described steps to make detached ADUs permitted in R and RS inside the urban overlay, with size limits calibrated to lot size and a careful evaluation of whether an ADU could be separately owned. "That's not something we look at lightly, and we would wanna think very carefully not just about the ownership and how that changes the dynamic of it, but also what that means for short term rentals," Claxton said. He added that staff's expectation is that ADUs would not produce a substantial number of new homes but would increase household flexibility.

Claxton also proposed simplifying duplex rules in R districts so parcels that meet minimum lot size could host two units, removing a long, historic set of conditions that now require staff and code officers to check parcel histories. Staff estimated approximately 87,000 parcels in Davidson County zoned in R districts; after excluding condos, parks and the like there are about 60,000 parcels, of which roughly 26,000 already would be eligible for duplexes, 15,000 lie in PUDs, about 10,000 are below minimum lot size, leaving roughly 8,000 parcels — about 10% of the R‑zoned stock — that could be affected by a duplex rule change.

The presentation turned to the conventional versus alternative development standards used across corridors and transit areas. Claxton said most parcels still use the conventional, suburban‑oriented standards while only about 1,500 acres use the alternative standards that encourage build‑to lines, narrower setbacks and more walkable form. He described the conventional height control plane (a rising plane measured from setbacks) as producing hard‑to‑predict maximums on deep or irregular lots and said staff is considering replacing some step‑back requirements and adjusting build‑to depths and alley access rules to improve predictability for builders and neighbors.

On affordability policy, Claxton described a state‑enabled rental affordability bonus limited to rental housing (not homeownership). The bonus would offer additional entitlements — for example extra height, bulk, or density — in exchange for some portion of units restricted to affordability. "It could be 5%. It may be 10%." he said when describing the likely share of units produced under the bonus as modeled so far, and stressed the calibration task is to set an exchange that produces meaningful affordable units without rendering projects unviable.

Staff showed two new residential districts under study: a residential neighborhood (RN) district aimed at house‑scale forms such as duplexes, plex houses and manor houses, and a residential limited (RL) district aimed at courtyard flats, multiplexes and low‑rise flats. The consulting team has translated those two district concepts into context‑specific variants (suburban vs. urban) and into form‑based controls: maximum main‑body width and depth, smaller secondary wings, and requirements for common open space in courtyard forms.

Commissioners asked procedural and design questions. Commissioner A asked how the proposed change to allow two family units would differ from current code; Commissioner A noted the code currently permits two‑family units "with conditions" and staff said the existing rules are lengthy and often require parcel‑by‑parcel research. Commissioner B asked for clarification about half stories and basements; Claxton said half stories refer to finished space under a pitched roof and that basements are counted only under existing code rules based on exposure and grade. When a commissioner asked whether step backs — recessed upper floors intended to provide visual relief — would be removed, Claxton said staff is studying the effect and noted in some cases a small required step back has produced a "wedding cake" form that did not provide pedestrian‑level relief.

Claxton said staff intends to bring formal recommendations for zoning code changes in June and continue community engagement thereafter to test rezoning options and recommended district boundaries against the Nashville Next growth and preservation concept map. He listed upcoming outreach events, including a workshop at James Lawson High School in Bellevue, a virtual presentation on June 2 and a planned Spanish‑language virtual session likely on June 5.

No formal motions or votes occurred during the workshop; the session was a staff briefing and discussion to shape recommendations for later formal action by the commission.