Finished Basement Building Code Cheat Sheet
When finishing a basement in Massachusetts, it's essential to adhere to local building codes to ensure safety and compliance. Here are some key requirements to consider:
General Considerations:
Building Code Reference: Massachusetts follows the 10th edition of the Massachusetts State Building Code (MSBC), which incorporates the International Residential Code (IRC) with state-specific amendments.
Always obtain the necessary building permits before starting work.
Room Dimensions:
Habitable rooms must have an area of at least 70 square feet, with no dimension less than 7 feet.
Habitable spaces in basements must have a minimum ceiling height of 6’ 8”.
Hallways cannot be less than 36 inches in width.
Emergency Egresses:
Each finished basement must have two egresses, one emergency escape and rescue opening. For example, a window or door leading directly outside.
Windows used for egress require a sill height of no more than 44 inches above the finished floor and provide a minimum net clear opening of 5.7 square feet. [See additional requirements in the diagram below]
If the window opens into a window well, the well must have a minimum horizontal area of 9 square feet. [See additional requirements in the diagram below]
Stairways:
Basement stairs dimensions have a minimum width of 36 inches and a minimum head clearance of 6’8”.
A light source must illuminate all treads and landings, controlled by switches at the top and bottom of the stairs.
Handrails are required on stairs with four risers or more. Handrails must return back into the wall, should not project more than 4.5 inches, and should be 34–38 in above the stair tread nosing.
Risers must be a minimum of 4” and a maximim of 7-3/4”. Ideally 7”.
A stair tread is ideally 11”, including an overhang of 1”.
Electrical:
Install smoke alarms at the bottom of the basement stairs in each basement bedroom and within 10’ of each bedroom.
Smoke alarms must be hardwired with battery backup and interconnected so that when one is activated, all will sound.
A carbon monoxide alarm must be installed in the utility area.
Carbon monoxide alarms should be installed on each story of the building as per code.
Bathrooms shall be equipped with a fan vented directly to the outside. A fan is not required if the bathroom contains a window with an opening of 1.5 square feet or more
Outlet receptacles must be installed within 6 feet of all wall breaks such as a door or window that is 24” or larger, and 12 feet thereafter.
A switch-controlled light must be installed at the top and bottom of stairs.
All habitable rooms must have either a switched light fixture or a switched outlet.
Insulation:
As of 12/27/24, basement walls should be insulated to a minimum of R-19 with a vapor barrier installed on the warm side of the wall.
Closed cell insulation is highly recommended as it is energy efficient and also serves as a vapor barrier
Miscellaneous:
Basement renovations over 1,000 sqft requires may be subject to additional HERS requirements.
If a room is intended as a bedroom, the room must have two qualifying egress exits and meet fire prevention requirements. Also talk to your building department if you are on septic or private sewer.
Make up and combustion air must be addressed.
Space under stairs shall be protected with ½-inch drywall and mineral wool requirements on the underside or with a non-accessible enclosure clad in ½-inch drywall.