5 rules for unincorporated Howard County, Maryland.
Verified from official government sources
Howard County permits an accessory dwelling unit inside an owner-occupied single-family home. The owner must live in the principal dwelling or the ADU, and a permit from the Department of Planning and Zoning is required. Recent Council Bill 3-2026 expanded ADU options countywide.
Howard County Zoning Regulations § 128.0.13 (Accessory Apartments)
The accessory apartment must be located within an owner occupied dwelling. The owner may occupy either the principal dwelling or the accessory apartment... In all dwellings, an accessory apartment shall occupy no more than one-third of the net floor area of the building, up to a maximum of 1,500 square feet.
Howard County caps the total footprint of all detached accessory structures, including sheds, on a single-family lot. On lots in the public water-and-sewer service area the cumulative maximum is 600 square feet; larger caps apply to rural RC and RR district lots by acreage.
Howard County Zoning Regulations § 128.0.12 (Detached accessory structures)
The maximum cumulative lot coverage permitted for all of the accessory structures located on any given residential lot developed with a single-family detached dwelling is: (a) 600 square feet for a lot in the planned public water and sewer service area. (b) 1,200 square feet for a lot in the RC or RR district which is 2 acres or less.
In Howard County a detached garage is an accessory structure that cannot contain a full bathroom, full kitchen, or living quarters. Converting a garage into a dwelling requires meeting the accessory-apartment rules under Section 128.0.13 and a Department of Planning and Zoning permit.
Howard County Zoning Regulations § 128.0.12.b
Restrictions for accessory structures. Full baths, full kitchens, residential habitation and commercial uses are not permitted in accessory structures.
A carport in Howard County is an accessory structure subject to Section 128.0 zoning rules. Detached accessory garages and sheds have zero-foot side and rear setbacks on single-family detached lots, while other accessory structures must sit five feet from side and ten feet from rear lot lines.
Howard County Zoning Regulations § 128.0 (accessory structure setbacks)
The required setbacks from side or rear lot lines for accessory structures on lots improved by single-family detached dwellings shall be as follows: (1) Detached accessory garages or sheds — 0 feet (2) Other accessory structures (a) Side — 5 feet (b) Rear — 10 feet.
Howard County has no standalone tiny-home zoning category. A permanent tiny dwelling is regulated as an accessory apartment under Section 128.0.13, which requires an owner-occupied property, limits floor area, and requires a Department of Planning and Zoning permit. Tiny houses on wheels are treated as trailers, not permanent housing.
Howard County Zoning Regulations § 128.0.13.c
In all dwellings, an accessory apartment shall occupy no more than one-third of the net floor area of the building, up to a maximum of 1,500 square feet.
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