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ID 234 Building CodesFall 2012
Vertical Components of Egress
Multi-step process
Design compartmentation (egress) system
Calculate occupancy Calculate width of stair Calculate rise and run of stair Lay out stair on all levels Lay out adjacent spaces (areas of
refuge, lobbies)
Means of Egress:
A continuous and unobstructed path of
travel from any point in a building to it’s
exterior or public way.
Step 1
multi-story egress diagram
…with a lobby
Defend in place: no sprinklers
Areas of Refuge
Step 2
Half Diagonal Rule(1/3 with sprinklers)
Practice problem:
1-4 Offices 5 Cafe
Practice problem:
14’-0” Floor to floor height Fully sprinklered How many exits required? What is minimum separation of exits? What is dimension of the stairs
Step 3
Area Allowance per occupant
Sample calculation
Number of Exits
Step 4
780 CMR Section 10
Step 5
dimensional requirements
Minimum width 44” (non-residential) Rise = 7” maximum Run = 11” minimum Cannot narrow from top to bottom Landings every 12’-0” vertical
(maximum) Guard rails when drop >27” Handrails both sides Handrail extensions
Stair dimensions
Overall stair dimensions
Guard rails
Guard rails
in our practice problem…
What is riser dimension? What is the length of the stair? What is the dimension of the stairwell?
other constraints still apply Door push and pull clearance Panic bars required Minimum head height = 80” Protruding objects: 4” maximum Threshold dimensions Door closers required Maximum area of glass in door: 144 sq.
in. No windows allowed Minimum light level: 11 lux (1
footcandle)
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