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Things to consider when converting an attic to living space.
- Headroom must be at least 7 feet from finished floor to ceiling. A habitable room must be at least 70 square feet with a minimum horizontal dimension of 7 feet. No part of the room less than 5 feet in height may be considered in the calculation. At least ½ of the required room size must be 7 feet in height. A plan must show at least a 3½-foot wide swath of room 35 feet in area at least 7 feet in height.
- Insulation – New habitable space must be insulated to R-49. Knee walls must be insulated to R-21. Single joisted vaulted ceiling must be insulated to R-38. Additionally, a 1” airspace must be provided above the insulation, ventilated at the top and bottom. Often times the existing rafters must be furred down to accommodate the insulation and ventilation, a process which may reduce headroom.
- Ceiling joists directly below the attic are often not designed to support furniture and living space above. The plans must show the size, the spacing, and the length of these members between supports.
- Internal stairs are required to connect the lower floor(s) to the new habitable space. If there are existing stairs, the risers cannot exceed 8”and the treads cannot be less than 9”. The tread depth and the rise heights must be consistent to within a 3/8” tolerance. The minimum headroom must be 6’ 8” measured from the nose of each tread. The width of the stairway may not be less than 32”. The stair must have at least one handrail. Light switches and landings are required at the top and bottom of the stairs. Any new stairs must meet higher standards not addressed here (36” wide, tread having maximum rise of 7” rise, minimum run of 10”, etc.).
- Egress – Any bedroom must have an emergency egress window with 5.7 square feet of openable area with a sill height of 44” maximum above the floor. Interconnected, hard-wired smoke detectors are required both inside and outside bedrooms.
- Heating must be provided.
- Plans – Your plans must show in detail that the work will comply with code. Plans must be indelible, reproducible, to scale, complete with floor plans and sections. Headroom, insulation, ventilation, rafter and joist spans are best shown in a sectional cut through the building.
