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)