Short answer
Do I need a permit to build a garage in Baltimore County?
Yes. Any accessory building over 120 square feet needs a permit, and an attached garage is an addition that always needs one. On historic, floodplain or Critical Area lots, any size needs a permit.
| Project | Baltimore County permit? |
|---|---|
| Detached garage over 120 sq ft | Yes, residential accessory structure permit |
| Attached garage | Yes, addition permit |
| Any garage or shed on a historic, floodplain, Critical Area or landmark lot | Yes, at any size |
| Electrical or plumbing work | Yes, pulled by a licensed electrician or plumber |
| Converting a garage to living space | Yes, addition and alteration permit |
1. Attached or detached?
Baltimore County treats anything attached to the house as an addition, not an accessory building, so an attached garage must meet the setbacks for the house itself. The county's zoning policy manual also treats a garage connected to the house by an open deck, porch or carport as part of the house. Detach it and it can be reviewed under the more flexible accessory building rules.
2. Where a detached garage can go
| Rule | Detached garage or accessory building |
|---|---|
| Location | Rear yard, behind the rear foundation wall of the house |
| Side and rear setback | 2.5 ft from the lot line |
| Within 5 ft of a lot line | One-hour fire-rated wall with no openings on that side |
| Alley | At least 15 ft from the alley centerline |
| Corner lot | In the half of the lot farthest from the side street |
| Height | 15 ft maximum |
| Coverage | No more than 40% of the rear yard |
| Size | No larger than the footprint of the house |
Anything outside these limits, such as a side-yard garage or a taller carriage house, needs a zoning variance. Accessory buildings aren't allowed on a vacant lot; the lot has to be combined with the one the house sits on.
3. What to submit
For a detached garage, the county asks for a signed accessory structure letter and a site plan; lots on a well or septic system follow the county's groundwater site plan requirements. Construction plans are required at 1,000 square feet and over, and garages over 400 square feet need footings below the frost line. The county requires a Maryland Home Improvement Commission licensed contractor for the work. For an attached garage, the addition permit needs a site plan, construction plans at 600 square feet or more, an energy code selection form and the contractor's MHIC license number.
4. Fees, inspections and timing
The county charges a $75 residential application fee plus a permit fee set by structure type and size (accessory structures under or over 1,000 square feet, additions under or over 600 square feet). Fees are calculated by the county and paid online. Inspections are booked through the online portal, with the approved plans on site. A permit expires one year after it's issued, or after six months if work hasn't started. Electrical and plumbing work need their own permits by licensed trades; in Baltimore County, plumbing permits require a county-licensed plumber.
5. Historic, floodplain and waterfront lots
On a landmark property or in a historic district, in the floodplain or in the Chesapeake Bay Critical Area, every accessory building needs a permit regardless of size. In the 100-year floodplain, the garage must be anchored and vented. See our Baltimore County permit guide for historic district review.
6. Converting a garage
Turning an attached garage into a bedroom, office or family room is an alteration that needs a permit, with construction plans if it creates a bedroom. On a well and septic lot, adding a bedroom also means showing the septic system can handle it. An in-law apartment inside a single-family house needs a county use permit.
