Codes, Regulations, and Life Safety for Residential Interiors
This domain tests whether you can keep a residence legal and survivable: egress, stairs, guards, emergency escape openings, smoke and carbon monoxide alarms, electrical protection, and the accessibility rules that apply to multifamily work.
Core rules
- Stairs (IRC): riser max 7-3/4 in, tread min 10 in, nosing 3/4-1-1/4 in, width 36 in, headroom 6 ft 8 in, handrail 34-38 in above tread nosings, guard 36 in min with balusters that stop a 4 in sphere.
- Emergency escape and rescue opening: 5.7 sq ft clear, min 20 in wide and 24 in high, sill max 44 in above the floor, operable without keys or tools.
- Smoke alarms in each bedroom, outside each sleeping area, and on each level, interconnected; CO alarms near sleeping areas where fuel-burning appliances or attached garages exist.
- GFCI in bathrooms, kitchens, laundry, garages, outdoors, and within 6 ft of sinks; AFCI protection on bedroom and living-area circuits; tamper-resistant receptacles.
- Guards required where the drop exceeds 30 in. Hallways 36 in min; egress doors 32 in clear; 7 ft ceiling in habitable rooms, 6 ft 8 in in baths and halls.
Worked example
A 9 ft floor-to-floor stair: 108 in divided by a 7.5 in target riser gives 14.4, so use 15 risers at 7.2 in each. Treads equal risers minus one: 14 x 10 in = 140 in (11 ft 8 in) of run plus landings. Then verify 6 ft 8 in headroom under the floor above and confirm the handrail height measures 34-38 in vertically from the tread nosings, not along the rake.
Traps
- Forgetting that finish floor thickness changes every riser equally.
- Missing a guard at a 30 in drop or at the open side of a stairwell.
- Assuming an older building is exempt - the alteration itself triggers compliance.
- Placing a single CO alarm in the basement instead of near sleeping areas.