Means of Egress I
1.
1I. Definition of a means of egress system: "…a continuous and unobstructed path of vertical and
horizontal egress travel from any point within a building or structure to a
public way"
A. Three elements of an egress system
1. Exit access
2. Exit
3. Exit discharge
I1I. Three parts of an egress
system (Slide
2 and 3) (IBC 1002)
A. Exit Access
1. Begins at any location
within the building.
2. Follows a path through the
building.
3. Ends when it reaches the
door to an exit enclosure, horizontal exit or exit passageway, exterior exit
stair, or exterior door at ground level.
4. Travel distances are
regulated.
5. Corridors are considered
part of the exit access.
B. Exit
1. The portion
egress travel where the occupant has attained a level of protection.
2. The occupant
has passed into a place where they are separated from any problems within the
building.
3. Travel
distances are no longer a concern
4. May bean:
a. exit enclosure
b. exit passageway
c. exterior exit stair
d. exterior door at ground level
C. Exit discharge
1. The last portion of the
three part egress system.
2. Includes the portion of the
means of egress where the occupant leaves an exit and continues until they
reach a public way.
3. May consist of yards or
egress courts.
4. Is almost always at ground
level.
D. Design Occupant Load (Slide 4) (IBC 1003.2.2.2)
E. Calculating Design Occupant Load
1. Three ways allowed
a. Actual number
b. Number by Table - Table
1003.2.2.2
c. Number by combination -
occupants merge in exits.
2. Actual number
a. Rarely used.
b. Only unique buildings where
the actual number of people occupying the building can be anticipated with certainty.
F. Occupant Load by Table (Slide 5) Most common method
1. The number of occupants for
whom means of egress shall be provided.
2. One occupant per unit of
area from Table 1003.2.2.2
"Occupant load
factors"
3. It is assumed all areas are
occupied at all times.
G. (Slide 6)
1. For most occupancies, gross floor areas are used.
2. Some occupancies allow the
"net" floor area to be used, deducting areas such as corridors,
stairways, toilet rooms, equipment rooms, and closets.
3. Where fixed seats are
installed the code specifies that the occupant load be the number of fixed
seats.
4. For benches, one occupant
per 18"
5. For booth seating, one
occupant per 24"
H. Design Occupant Load (Slide 7)
1. Number by Table (Slide 6)
a. Use Table 1003.2.2.2
b. Contains occupant load
factors
c. Not the same as
2. Number by combination -
probably most widely used.
I. Egress Convergence (number by combination) (Slide
8)
1. Egress convergence
2. Add occupant loads together
as loads converge on the egress path.
3. Once occupant load is
established
4. Components sized to
accommodate anticipated occupant load.
5. Minimum widths of
components often dictate capacity of
6. The exit. When using
multiple exits, the required width can be divided amongst the separate exits.
J. Outdoor areas (IBC 1003.2.2.10) (Slide 9)
1. Yards, patios, courts, etc.
shall be provided with a means of egress.
2. Where outdoor areas are
used by others, and the egress is through the building, the occupant load from
outside is added to the building occupant load.
K. Egress Width - Means of Egress (Slide 10) (IBC
1003.2.3)
1. Table 1003.2.3
2. Total width of egress in
inches shall not be less than the total occupant load multiplied times the
factors in Table1003.2.3.
3. When more than one means of
egress is available, it cannot reduce the capacity by more than 50% of the available.
4. The most restrictive
element (the narrowest) establishes the overall capacity.
L. Min. Ceiling Height - means of egress headroom. Pg.
189. (Slide 11)
M. Stairwell widths. See diagram on P 187 of the text.
(Slide 12)
1. Width of stairways from
multi-story buildings (Section 1003.2.2.6)
2. As long as occupants are headed in the same
direction, there is no need to combine loads from floors to calculate stairwell
widths.
3. Stairs are required to be
wider than corridor. Compare width factors on Table 1003.2.3.
5. Exit speed is less than in a corridor - everyone
takes the same size steps.
N. Stairway widths. pg. 206 (Slide 13)
O. Stair tread and riser requirements pg.207 (Slide 14)
P. Stair landings pg. 209 (Slide 15)
Q. Guards pg.195 (Slide 16)
R. Handrail locations pg.212- (Slide 17)
S. Handrail dimensions pg. 214/5 (Slide 18)
T. Doors (Slide 19)
U. Door height and width (Slide 20)
V. Door swing (Slide 21)
W. Elevation Change (Slide 22)
X. Door arrangements pg. 201 (Slide 23)
1. Door encroachment - See
diagram pg. 188 VERY IMPORTANT.
Y. Slide 24 - Landings at doors - Very important pg. 20
I
Z. Slide 25 - Floor elevation at doors. Pg. 200
AA. Locks and latches pg. 203 (Slide 26)
BB. Panic hardware - all doors
must be openable without means of a key, in the direction of egress travel. pg.
203/5 (Slide 27)
1. Some exceptions for M
occupancies "This door to remain 00 unlocked during business hours." Over
100 occupants
CC. Accessible means of egress
- At least one accessible means of egress is required from any accessible
space. A maximum of two is required when the required means of egress is two.
(Slide 28)
DD. Areas of refuge - behind a
firewall and provide safety until persons can be evacuated. Must be provided at
each floor. Enough to provide wheelchairs without reducing the overall exit
width. 2-way communication required. Size must be at least enough for one 30 x
48 wheelchair. (Pg. 196) (Slide 29)
EE. Exit signs - Where required (IBC 1003.2.10)
pg.191/3 (Slide 30)
FF. Exit sign illumination (IBC 1003.2.10.4) (Slide 9)
GG. Ramps 1:12 max.
Anything greater than 1:20 is a ramp pg. 216/7