Rental conversions in Montgomery County

An attached accessory dwelling unit may have up to 1,200 square feet of gross floor area, including cellar space, or the full square footage of the basement or cellar if only that level is used; a detached one is limited to the least of 50% of the main house's footprint, 10% of the lot area or 1,200 square feet.⁷ The accessory dwelling unit must be the only additional living unit on the lot, with no other tenants, boarders or short-term rentals such as Airbnb, and no more than two adults may live in it.⁷

With an existing driveway, an accessory dwelling unit needs one on-site parking space beyond what the main house requires, or two spaces if a new driveway must be built; no on-site space is required within one mile of a Metrorail, Purple Line or MARC station.⁷ Check the walking distance to the nearest Metrorail, Purple Line or MARC station before you plan a new driveway.

The unit needs a separate entrance on the side or rear of the house that leads directly outside and not through a garage; a front entrance is allowed only if it is shared with the main house or the unit's front door existed before May 20, 2013.⁷ The unit's entrance door must be side-hinged with a clear width of at least 32 inches and a clear height of at least 78 inches, and double-cylinder deadbolts must be replaced with thumb-turn deadbolts.⁷

The Class 3 accessory dwelling unit application fee is $615: a $260 filing fee, a $230 public notice sign fee and a $125 annual license fee.⁷ DHCA checks an accessory dwelling unit application for completeness within 5 business days, the owner must post a public notice sign for at least 30 days, and the license is approved 30 days after the Director's report if the unit complies.⁷

An accessory dwelling unit in a finished basement or cellar needs a ceiling at least 6 feet 8 inches high, with beams, girders, ducts or other obstructions allowed down to 6 feet 4 inches, and the ceiling must be finished drywall.⁷ Every sleeping room in the unit needs an operable window or exterior door for emergency escape; a window at or below grade needs at least 5 square feet of net clear opening, at least 24 inches high and 20 inches wide, with the opening no more than 44 inches above the floor.⁷

A basement stairway used as the unit's exit must be at least 36 inches wide, or 32 inches if existing, a furnace may not sit under it, and a sleeping room next to a utility room with a fuel-burning furnace or water heater needs a weather-stripped, self-closing door between them.⁷ The unit's kitchen needs a stove at least 24 inches wide, a standard refrigerator and a 36-inch clear passageway, its cooking area needs two circuits of at least 20 amps, and bathroom outlets must be GFI-protected on a 20-amp circuit.⁷

Carbon monoxide alarms are required in all rental dwelling units, whether or not they have fuel-burning equipment, outside each sleeping area and on every occupiable level including basements.⁷ The U.S. Fire Administration says homeowners and landlords should put smoke alarms in every bedroom, outside each sleeping area and on every level, test them monthly, and replace them 10 years from their manufacture date.¹³

Single-family and condominium owners in Montgomery County who rent out their property must get a rental housing license every year, and rental properties built before 1978 must meet Maryland's lead poisoning risk reduction requirements.¹⁴ Since July 1, 2023, Montgomery County law has required radon testing in single-family and multifamily rental housing, including condominiums, with disclosure and mitigation of radon above an action level, administered by DHCA.¹⁵

EPA's lead renovation rule generally doesn't cover homeowners working on their own pre-1978 homes, but it does apply if you rent out all or part of your home.¹⁶ Before a renter signs a lease for most pre-1978 housing, federal law requires the landlord to disclose known lead-based paint and hazards, share available records, hand over EPA's Protect Your Family From Lead pamphlet and include a Lead Warning Statement.¹⁷

Montgomery County's Zoning Text Amendment 19-01, in effect since December 31, 2019, removed the requirement for conditional use approval for accessory apartments and allows detached accessory dwelling units as a limited use in the R-200, R-90 and R-60 zones.¹⁰ Older special-exception apartments follow different paperwork, so ask the county which license yours falls under if the unit already exists.

More than one in four adults 65 and older fall each year.¹⁸ Some owners build an accessory apartment for a parent instead of a renter, and the county's license applies either way. A step-free path from the parking space, a curbless shower and lever handles cost little more when they're in the first drawings. NAHB's Certified Aging-in-Place Specialist (CAPS) credential trains remodelers in home modifications for aging in place.¹⁹

Calling the number on this page puts you through, on a recorded line, to one independent company that handles rental conversions in the Montgomery County area. The design, the schedule and the price are agreed between you and that company.

The company pays us for each call, so connecting costs you nothing, and nobody from our side calls or texts you afterward. How we make money

Look the company up with the state before any money changes hands. Maryland's Home Improvement Commission licenses home improvement contractors and salespersons, and its License Search shows whether a license is current.²⁰ Check a Maryland license

Then ask who will pull the building permit, and line it up with the county's preliminary inspection. Homeowners may apply for an alteration permit in their own name, but when a contractor does the work the county strongly suggests listing the contractor as the responsible party, and a contractor must hold a Maryland Home Improvement Commission license to obtain a permit.²¹