City staff demonstrate lot-buildability tool, estimate ~2,400 potential units on vacant lots with permit-ready plans

City planning staff on July 24 demonstrated a lot-buildability mapping tool designed to match Grand Rapids parcels with the city’s permit-ready plan sets for single-family, duplex and four-family buildings and to help identify where code changes could unlock additional housing supply.

Planner Rowan Brady, who led the demonstration, said the tool filters parcels by zoning, lot size, street type and other dimensional requirements and checks them against the smallest of the permit-ready plan options so users can quickly see where those plans would meet current zoning standards. “We used these plans and analyzed all of the properties in the city based on the requirements of our zoning code,” Brady said, noting the tool is still in development and that staff plan to refine environmental and other exclusion layers.

During the demonstration staff showed that, using the permit-ready plans and focusing on vacant parcels, the tool produced an estimated total of roughly 2,400 potential dwelling units (about 1,300 units in quadplex form plus additional units in duplexes and single-family plans) on parcels classified as vacant and not otherwise excluded. Brady cautioned that environmental constraints (steep slopes, wetlands) and data-source limits could reduce that number and that the counts reflect the smallest plan options loaded into the tool.

Commissioners asked about accuracy and public release. Brady said the tool uses public assessor and parcel data (Kent County) and that the city has conducted iterative truth-testing; staff plan a disclaimer and a public-facing interface that will let users hide or display particular parcel details. Commissioner discussion suggested a short pilot period for commissioners to test the tool and proposed using it as a policy aid for the upcoming zoning ordinance update, especially to examine how density, lot-width and setback rules affect the number of buildable parcels.

Staff said the tool can help identify zoning provisions that remove otherwise-dimensionally-eligible lots from being buildable because the use is not permitted by right. An example shown to commissioners found more than 20,000 parcels where a duplex would meet dimensional requirements but is not permitted by right in the parcel’s zone.

Brady said the city is exploring whether more interactive, real-time inputs (allowing a user to load custom building dimensions) are feasible; current functionality applies the precomputed checks from the permit-ready plan sets and permit templates. Staff will provide commissioners access for hands-on testing and may use a retreat or workshop session to walk commissioners through the tool before any code changes are proposed.