Smithville planning commission backs ADU ordinance with separate-structure rule, 400-sq.-ft. minimum

The Smithville Planning and Zoning Commission voted to recommend an accessory dwelling unit ordinance that requires ADUs to be separate structures, sets a 400-square-foot minimum and caps units at 90% of the principal dwelling.

The recommendation, made after a public hearing and several amendments, was intended to provide clearer size, safety and aesthetic standards for ADUs while keeping the regulation consistent with building-code limits and conditional-use review. Commission staff said the changes respond to concerns about tiny structures, conversions inside existing homes, and exterior access that can affect neighborhood character.

Jack, Smithville’s development director and acting planning director, told the commission the ordinance must align with building-code requirements and the International Residential Code, so percentage-based minimums could be overridden by construction rules. “I could change that language that the ADU is not less than 400 square feet,” Jack said during the discussion. He also described fire-separation and heating/cooling complications if an ADU were placed inside an existing dwelling, a point that prompted members to debate whether ADUs should be allowed within existing structures.

Commissioners discussed a range of issues before voting, including: - Whether an ADU may be inside an existing structure (attic, basement or garage conversion) or must be a separate, detached building; the commission directed that ADUs shall be separate structures. - Minimum and maximum size: commissioners agreed to a 400-square-foot minimum and a maximum of 90% of the primary structure’s area, with a caveat that building-code minimums override percentage rules. - Aesthetics, parking and neighborhood value, with repeated concerns that very small, prefabricated “tiny homes” or visible exterior stair access could harm neighborhood character. - Screening of access points: members approved language that access points to ADUs within an existing structure shall be adequately screened, leaving detailed standards to conditional-use review.

The commission also discussed the permitting process. Staff framed ADUs as subject to a conditional-use permit in order to set standards for screening, parking, and site plans. Jack noted conditional-use review would allow the commission to require screening and other site-specific mitigations.

The commission voted to approve the ordinance as amended. Mayor Bole, Terry, John Wallace, Alderman Wilson, John Chevalier and Billy voted “aye” on the final motion approving the ordinance as amended.

The commission’s recommendation goes to the Board of Aldermen. Staff said the ordinance and related exhibits — including the planning commission’s required statement on ADUs — will appear on the Board’s agenda at the next meeting, with final readings expected in the coming weeks as the Board’s schedule allows.

Officials emphasized the limitations of local regulation where state or national code applies: the commission’s size limits will be applied alongside the IRC and other building-code standards. Staff also noted that the conditional-use framework preserves discretion to place additional screening, parking and site design conditions on individual ADU proposals.