Anne Arundel County, MD Accessory Structures: Tiny Homes (2026)

Anne Arundel County allows tiny houses built on a permanent foundation as either a primary dwelling or an accessory dwelling unit (ADU). As of July 2024, Maryland HB 20 requires the county (population >75,000) to permit at least one ADU on each single-family lot, with no owner-occupancy requirement, no added parking requirement, and setbacks not exceeding primary-structure setbacks. Tiny houses on foundations must meet IRC Appendix Q: minimum 70 sq ft habitable room; ceilings ≥6'8' in main spaces, 6'4' in bathrooms and kitchens; loft access via stair, ladder, or alternating-tread device; emergency egress from sleeping lofts. Minimum dwelling size under Article 18 is generally 220 sq ft. Tiny houses on wheels (THOW) are classified as RVs under Maryland Transportation §11-141 and may not be used as permanent dwellings on private lots — they may be parked for storage per Article 18 RV rules or occupied temporarily in a licensed RV park. Critical Area ADU construction is subject to RCA/LDA impervious caps and buffer rules. On-site wastewater (BAT septic) upgrades are typically required along the Severn, Magothy, South, and Patuxent watersheds.