What Size Does a Basement Have to Be to Put in a Full Bath?

Plan Around Bathroom

• The basement itself must accommodate a standard bath floor plan. A 5-by-7-foot bathroom is considered a standard bath size. Some builders say that a 5-by-8-foot bath is a more acceptable standard. The actual basement must encompass a staircase from the floor above, one or more rooms and a hallway. Some building codes specify a 3-foot hallway in bedroom and bath areas of basement construction. If the basement measures approximately 24 by 18 feet, this will be sufficient room.

Ceiling Height Codes

• Fitting the fixtures into an insulated space with a sufficient ceiling height is important, too. It’s possible to have a bath ceiling of only 7 feet in a basement, but make sure your local building codes will allow this. Many state that a bath ceiling in a basement must be at least 70 inches high over the toilet area, so don't install a toilet under a sloping stairway, for instance. Get a permit and a copy of building restrictions and requirements.

Plan Around Heating

• Place the bathroom pipes near a heat source, if possible. Use graph paper to configure all bath dimensions so you can place the bath near furnace or heat pump ductwork. Well-placed soffit areas will hide overhead pipes and ducts. Placing one or two bath walls next to exterior basement walls that are underground will help insulate the room, too.

Shower-Only Option

• A half basement can accommodate a "downsized" full bath with shower only. While a bathtub-shower combo is handy, it’s possible to use less than 5 by 7 feet of space if you build a small tiled shower rather than incorporate a bathtub. If only half your basement is dug out, you can create a full bath if you really need one. Having a backyard pool, for example, might call for including a shower for family and visitors in the basement space.

Visual Appeal

• Plan the ceiling space and surrounding hallways carefully before starting bath construction. For instance, take into consideration any needed ductwork coming through the bath. You don’t want the ceiling to be so cramped it affects the visual appeal of the bathroom. You might, as one option, channel ductwork with a vent to the side wall of the bath area to save space. Be sure to build a hallway between the bath and direct living space, if possible, to create more privacy in the bath area.