Derwood Accessory Structures: Tiny Homes Rules (2026)

Montgomery County does not have a standalone tiny home ordinance. Small permanent structures intended for habitation are regulated under the county building code (based on the IRC) and zoning ordinance. A tiny home on a permanent foundation that includes a kitchen, bathroom, and sleeping area may qualify as an Accessory Dwelling Unit under ZTA 19-01, subject to the ADU size, setback, and owner-occupancy requirements. Minimum habitable room standards apply: 7-foot ceiling height, at least one room of 120 square feet minimum, egress windows, and compliant electrical, plumbing, and mechanical systems. Tiny homes on wheels (THOWs) are generally classified as recreational vehicles under Montgomery County zoning and may not be used as permanent residences. RVs may be parked on residential properties subject to parking and screening requirements but cannot be occupied as dwellings. Maryland does not have a statewide tiny home building code; local jurisdictions apply IRC standards. Some aspects of the IRC Appendix Q (Tiny Houses, adopted in the 2018 IRC) may be applied by DPS for tiny homes under 400 square feet on permanent foundations, including reduced ceiling heights (6 feet 8 inches in lofts) and alternate loft access provisions. Prospective tiny home builders should consult DPS pre-application review to confirm compliance before construction.