ADU Permit Drawings in Montgomery County, Maryland
Ben Norkin Architecture has put together detailed guidance on what drawings are required to obtain an Accessory Dwelling Unit (ADU) permit in Montgomery County, Maryland. While every site and project is different, the information below covers the core requirements that apply to most ADU projects — whether detached ADU builds, garage conversions, or backyard cottage additions.
It's worth noting that what's required for permitting and what's needed to actually construct the unit can differ. The list below focuses on permitting requirements. How information is organized within a drawing set is generally left to the architect's discretion, but the following represents the minimum that needs to appear somewhere in the plans.
Required Drawings for an ADU Permit
Architectural Site Plan
This drawing must show property boundaries, the existing house footprint, and parking if required. It also needs to include the footprint, dimensions, and location of the proposed ADU, along with required property setbacks.
Zoning Information
Plans must include allowable and proposed lot coverage calculations, the allowable and proposed size of the accessory dwelling unit, and the ADU's height. The property address, zone, subdivision, lot, block, and Tax ID are also required.
Drainage Information
A drainage plan may be required showing how rainwater will be managed on site — most commonly through a dry well. This includes grade contours, spot elevations at gutter downspout discharge points, corner elevations, and a technical drawing of the dry well construction.
Sediment Control
A sediment control permit may be needed, though most ADU projects fall below the size threshold that triggers this requirement. If applicable, drawings must show the construction area, limit of disturbance, and access path from the public right of way.
Floor Plans
Architectural floor plans need to show building and room dimensions, door and window locations, tempered windows where required, and egress windows in bedrooms. Kitchens must include cooking appliances, a sink, a refrigerator, and cabinet and counter space. Energy efficiency compliance must also be documented.
Sections and Elevations
A building section from foundation to roof ridge is required, showing structural assemblies, wall and roof construction, and window and door locations and materials.
Energy Efficiency
Plans must demonstrate compliance with current energy efficiency code, including insulation levels in the roof, walls, and below the slab or crawl space.
Structural Drawings
Required structural drawings include a foundation plan, a floor framing plan (if applicable), a roof framing plan, and a wind bracing plan.
What Is Not Required for the Building Permit
Mechanical, electrical, and plumbing work each require their own trade permits and do not need specific architectural drawings in Montgomery County. Fire sprinklers are required for a new detached ADU, but a sprinkler plan does not need to be submitted with the building permit application.
For the DHCA permit, an abbreviated version of the site plan and floor plans is generally sufficient. DHCA focuses primarily on the size, location, and living amenities of the unit, while DPS requires more complete drawings due to life safety considerations.
Ben Norkin Architecture offers services ranging from full ADU design and permitting to plan review for those who already have their own drawings or are working with a building designer. A plan review can help make the permitting process more straightforward and reduce the likelihood of unexpected issues along the way.
