105 CMR, § 410.452
The owner shall maintain all means of egress at all times in a safe, operable condition and shall keep all exterior stairways, fire escapes, egress balconies and bridges free of snow and ice, provided, however, in those instances where a dwelling has an independent means of egress, not shared with other occupants, and a written letting agreement so states, the occupant is responsible for maintaining free of snow and ice, the means of egress under his or her exclusive use and control. All corrodible structural parts thereof shall be kept painted or otherwise protected against rust and corrosion. All wood structural members shall be treated to prevent rotting and decay. Where these structural elements tie directly into the building structural system, all joints shall be sealed to prevent water from damaging or corroding the structural elements.
105 CMR, § 410.452