How Rockville Handles Accessory Structures: A Practical Guide

Rockville maintains 105 local ordinances across all categories, and 5 of those deal specifically with accessory structures. Here is a breakdown of what the city actually requires, what is prohibited, and where Rockville falls on the strict-to-permissive spectrum compared to other cities.

Tiny Homes

Rockville does not have a specific tiny home ordinance. Tiny homes on foundations may qualify as attached ADUs under the 2024 zoning amendment if they meet conditional use and size requirements. Tiny homes on wheels are classified as recreational vehicles and cannot serve as permanent dwellings. All habitable structures must meet the International Residential Code minimum standards adopted by the city.

Key details: Tiny Home Ordinance: None specific. On Foundation: Subject to accessory building rules. On Wheels: Classified as RV; no permanent occupancy. Min Room Size: 70 sq ft under IRC. Zoning Contact: 240-314-8211.

Occupying a tiny home on wheels as a permanent residence is a zoning violation. Unpermitted dwelling units face code enforcement action including fines up to $1,000 per day and orders to vacate. Structures that do not meet IRC minimum standards may be declared unfit for habitation. Contact Community Enhancement at 240-314-8330 to report concerns.

This is one of the stricter rules in Rockville's municipal code. If you are unsure whether your situation complies, it is worth checking with the city before proceeding.

Carport Rules

Carports in Rockville are regulated as accessory structures under Chapter 25 of the City Code and require a building permit. They must meet rear yard setback requirements of at least 3 feet from lot lines and cannot exceed the maximum height or coverage limits for accessory buildings. Carports in front yards are generally not permitted in residential zones.

Key details: Permit Required: Yes. Location: Rear yard in most residential zones. Min Setback: 3 feet from lot lines. Max Height: 12 ft at min setback; 20 ft maximum. Contact: 240-314-8247.

Building a carport without a permit is a code violation. Carports placed in front yards or within required setbacks may be ordered removed. Fines may reach $1,000 per violation per day. The Community Enhancement Division at 240-314-8330 investigates complaints about unpermitted structures.

ADU Rules

Rockville permits attached accessory dwelling units as a conditional use in residential zones under zoning text amendment TXT2023-00263, effective April 9, 2024. Attached ADUs may be built within or as an addition to single-unit detached homes. The property owner must occupy either the main dwelling or the ADU for at least six months per year, and the ADU cannot exceed 50 percent of the primary dwelling floor area.

Key details: Effective Date: April 9, 2024. Approval Type: Conditional use. Max ADU Size: 50% of primary dwelling floor area. Owner Occupancy: Required 6 months per year. Contact: 240-314-8211 or zoning@rockvillemd.gov.

Constructing or operating an ADU without conditional use approval constitutes a zoning violation. Unpermitted ADUs are subject to code enforcement action including fines and orders to cease occupancy. Fines may reach $1,000 per day for continuing violations. Existing unpermitted ADUs had a grace period through April 9, 2025, to obtain conditional use approval.

Shed Rules

Rockville requires a building permit for sheds and accessory buildings. Chapter 25 of the Rockville City Code sets a maximum footprint of 750 square feet for any single accessory building and 1,000 square feet total for all accessory buildings on one lot. Minimum setback is 3 feet from lot lines, with additional setbacks required for structures taller than 12 feet.

Key details: Permit Required: Yes, for all sheds. Max Single Footprint: 750 sq ft. Max Total Footprint: 1,000 sq ft all accessory buildings. Min Setback: 3 feet from lot lines. Max Height: 20 feet (cannot exceed main dwelling).

Building a shed without a permit is a code violation subject to fines and enforcement action. Structures that exceed setback, height, or size limits may be ordered removed or modified. Fines may reach $1,000 per violation per day. The city conducts curbside inspections and responds to resident complaints through the Community Enhancement division at 240-314-8330.

Garage Conversions

Garage conversions in Rockville require a building permit and must comply with zoning, building, and fire code requirements. Converting a garage to living space may be treated as an attached ADU under the 2024 zoning text amendment, requiring conditional use approval. The conversion must maintain required off-street parking spaces for the property.

Key details: Permit Required: Building + trade permits. ADU Rules: May require conditional use approval. Parking Impact: Must maintain required off-street spaces. Building Code: IRC habitable space standards apply. Zoning Contact: 240-314-8211.

Converting a garage without permits is a building code violation subject to fines up to $1,000 per day. Unauthorized dwelling units may be ordered vacated and restored to garage use. Loss of required parking spaces without a variance constitutes a zoning violation. The Community Enhancement Code Enforcement Division investigates unpermitted conversions at 240-314-8330.

The Bottom Line

Rockville's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Rockville is broadly strict or permissive.

Keep in mind that Rockville can amend these rules at any council meeting. For the most current version of any rule mentioned here, check the specific ordinance page, where we track updates as they happen.