What an in-law suite is
"In-law suite" is the family name for one kind of ADU: a complete small home — kitchen, bathroom, bedroom, living space, private entrance — built for someone you love. Most are attached additions joined to the main house (see attached ADUs), but a converted garage or a finished basement can serve the same purpose (see garage conversions). The form follows the family; the legal side follows the county's ADU rules either way.
Why families build them
Multigenerational living is one of the top two reasons homeowners build ADUs anywhere in the country. The math is simple: a suite for Mom costs less than assisted living, keeps her independent, and puts family — not a facility — twenty steps away. For a grown kid, it's a launchpad that beats paying someone else's rent. And when family no longer needs it, a properly permitted suite becomes a rental unit.
Designed for the person living there
A suite for an aging parent is designed differently from a rental unit. We plan for:
- No-step entry — a flush threshold at the private door, no stairs to climb with groceries or a walker.
- A walk-in shower with a bench and grab bars — the bathroom is where falls happen, so it's where safety starts.
- Wider doorways and hallways that a wheelchair or walker can actually navigate.
- A first-floor bedroom — everything daily on one level.
- Easy-grip handles, good lighting, and rocker light switches — small details that matter more every year.
Privacy for both generations
Closeness works when everyone can close a door. We design in-law suites with a truly private entrance, sound insulation in the shared wall, and separate heating and cooling zones — so nobody fights over the thermostat and nobody hears the 6am news through the drywall. Together when you want to be, apart when you don't.
How the county treats it
An in-law suite follows the same ADU rules as any other type. As an attached addition in Charles County's published draft (Bill 2026-06): the house plus suite must meet all zone setbacks together, the entry shouldn't be visible from the street, and size is capped at 1,000 square feet or 75% of the main house's floor area (whichever is smaller) on lots under 3 acres, with a 2-bedroom maximum and one ADU per lot. The county ADU permit comes before the building permit. (Published draft rules; final adoption being confirmed.)
Sources: Charles County Bill 2026-06 / ZTA 25-189 (published draft, §§3.01.700.E–I).
What it costs (honestly)
An attached in-law addition costs like new construction — foundation, framing, roof tie-in — while a converted garage or basement costs considerably less for the same purpose. Which route fits your family depends on your house, your lot, and your budget. Material prices move and every project differs, so treat site numbers as starting points. Your written estimate after the free visit is the real number.