Sumner County planning staff proposes strict rules to allow shipping containers in residential zones

Planning staff told the Sumner County Regional Planning Commission during a study session that county building and codes staff are drafting amendments to allow limited use of shipping containers in residential zones under strict conditions.

The proposal would require special-exception approval by the county Board of Zoning Appeals before a container may be placed on a residential lot, and would let the BZA impose screening, buffering or setback requirements. Containers used for storage or accessory purposes would be subject to the county's accessory-structure rules, building permits and zoning setbacks; containers used as dwellings would have to meet accessory-dwelling-unit standards or primary-structure requirements as applicable.

The staff explanation said existing county health-and-safety standards (adopted by resolution in 2003 and updated in 2008) and the county zoning code were not aligned and that the proposed text is intended to make the two documents consistent. Staff noted the current county practice prohibits shipping containers on residential lots except when used for agricultural purposes, but allows more flexibility on commercial and industrial lots.

Under the draft language presented, key measures would include: Board of Zoning Appeals approval as a special exception; a minimum 5-foot setback from property lines for containers placed behind the main dwelling; exterior encapsulation or approved cladding and painting to reduce visible metal surfaces; containers to be supported on continuous footing or elevated at least 18 inches with approved skirting and crawlspace access complying with the International Residential Code; and a prohibition on placing containers in the regulatory floodway. The draft also would bar above-ground storage containers on vacant lots smaller than five acres and require onsite certification for buried containers and dwellings by Tennessee-licensed engineers and architects, plus signed, sealed drawings for building permits.

Staff said inspections and enforcement would fall to existing codes personnel and noted enforcement is difficult across the county’s large unincorporated area with a small codes team. Staff described a 90-day limit to obtain a certificate of occupancy for residential storage use, with a possible 30-day extension at the building-and-codes director’s discretion; failure to secure a CO could prompt revocation of approvals by the Board of Zoning Appeals.

Commissioners and staff discussed practical enforcement concerns — for example, corrosion of steel containers, underground water table and moisture issues for buried units, and how to confirm structural integrity of used containers. Staff said third-party certified engineering reports would be required for buried or habitable containers. Staff also emphasized the county would treat containers used as dwellings to the same minimum-square-foot standards the county applies to other dwellings (county practice listed a roughly 300-square-foot minimum in the draft).

Staff said the code office and the construction board of appeals have reviewed drafts and that staff will bring a recommendation to the planning commission in coming months before any zoning changes are forwarded to the County Commission.