International Building Code Section 508


International Building Code 508.1

REQUIRED SEPARATION OF OCCUPANCIES (HOURS)

General. Where a building or portion thereof contains
two or more occupancies or uses, the building or portion
thereof shall comply with the applicable provisions of this section.

International Building Code 508.2

Incidental uses. Incidental use areas shall comply with
the provisions of this section.
Exception: Incidental use areas within and serving a dwelling
unit are not required to comply with this section.

Occupancy classification. An incidental use area
shall be classified in accordance with the occupancy of that
portion of the building in which it is located or the building
shall be classified as a mixed occupancy and shall comply
with Section 508.3.

Separation. Incidental use areas shall be separated
or protected, or both, in accordance with Table 508.2.

Construction. Where Table 508.2 requires a
fire-resistance-rated separation, the incidental use area
shall be separated from the remainder of the building by a
fire barrier constructed in accordance with Section 706
or a horizontal assembly constructed in accordance with
Section 711, or both. Where Table 508.2 permits an automatic
fire-extinguishing system without a fire barrier, the
incidental use area shall be separated from the remainder
of the building by construction capable of resisting the
passage of smoke. The partitions shall extend from the
floor to the underside of the fire-resistance-rated
floor/ceiling assembly or fire-resistance-rated roof/ceiling
assembly above or to the underside of the floor or
roof sheathing, or sub deck above. Doors shall be self- or
automatic closing upon detection of smoke. Doors shall
not have air transfer openings and shall not be undercut
in excess of the clearance permitted in accordance with
NFPA 80.

Protection. Where an automatic fire-extinguishing
system or an automatic sprinkler system is provided in
accordance with Table 508.2, only the incidental use areas
need be equipped with such a system.
INCIDENTAL USE AREAS

International Building Code 508.2.1

Occupancy classification. An incidental use area
shall be classified in accordance with the occupancy of that
portion of the building in which it is located or the building
shall be classified as a mixed occupancy and shall comply
with Section 508.3.

International Building Code 508.2.2

Separation. Incidental use areas shall be separated
or protected, or both, in accordance with Table 508.2.

Construction. Where Table 508.2 requires a
fire-resistance-rated separation, the incidental use area
shall be separated from the remainder of the building by a
fire barrier constructed in accordance with Section 706
or a horizontal assembly constructed in accordance with
Section 711, or both. Where Table 508.2 permits an automatic
fire-extinguishing system without a fire barrier, the
incidental use area shall be separated from the remainder
of the building by construction capable of resisting the
passage of smoke. The partitions shall extend from the
floor to the underside of the fire-resistance-rated
floor/ceiling assembly or fire-resistance-rated roof/ceiling
assembly above or to the underside of the floor or
roof sheathing, or sub deck above. Doors shall be self- or
automatic closing upon detection of smoke. Doors shall
not have air transfer openings and shall not be undercut
in excess of the clearance permitted in accordance with
NFPA 80.

International Building Code 508.2.2.1

Construction. Where Table 508.2 requires a
fire-resistance-rated separation, the incidental use area
shall be separated from the remainder of the building by a
fire barrier constructed in accordance with Section 706
or a horizontal assembly constructed in accordance with
Section 711, or both. Where Table 508.2 permits an automatic
fire-extinguishing system without a fire barrier, the
incidental use area shall be separated from the remainder
of the building by construction capable of resisting the
passage of smoke. The partitions shall extend from the
floor to the underside of the fire-resistance-rated
floor/ceiling assembly or fire-resistance-rated roof/ceiling
assembly above or to the underside of the floor or
roof sheathing, or sub deck above. Doors shall be self- or
automatic closing upon detection of smoke. Doors shall
not have air transfer openings and shall not be undercut
in excess of the clearance permitted in accordance with
NFPA 80.

International Building Code 508.3

Mixed occupancies. Each portion of a building shall be
individually classified in accordance with Section 302.1.
Where a building contains more than one occupancy group,
the building or portion thereof shall comply with Sections
508.3.1, 508.3.2, 508.3.3 or a combination of these sections.
Exceptions:
1. Occupancies separated in accordance with Section
509.
2. Where required by Table 415.3.2, areas of Group
H-1, H-2 or H-3 occupancies shall be located in a separate
and detached building or structure.

Accessory occupancies. Accessory occupancies
are those occupancies subsidiary to the main occupancy of
the building or portion thereof. Aggregate accessory occupancies
shall not occupy more than 10 percent of the area of
the story in which they are located and shall not exceed the
tabular values in Table 503, without height and area
increases in accordance with Sections 504 and 506 for such
accessory occupancies.
Exceptions:
1. Accessory assembly areas having a floor area less
than 750 square feet (69.7 m2) are not considered
separate occupancies.
2. Assembly areas that are accessory to Group E
occupancies are not considered separate occupancies
except when applying the assembly occupancy
requirements of Chapter 11.
3. Accessory religious educational rooms and religious
auditoriums with occupant loads of less than
100 are not considered separate occupancies.

Occupancy classification. Accessory occupancies
shall be individually classified in accordance
with Section 302.1. Code requirements shall apply to
each portion of the building based on the occupancy classification
of that accessory space, except that the most
restrictive applicable provisions of Section 403 and
Chapter 9 shall apply to the entire building or portion
thereof.

Allowable area and height. The allowable
area and height of the building shall be based on the
allowable area and height for the main occupancy in
accordance with Section 503.1. The height of any accessory
occupancy shall not exceed the tabular values in
Table 503, without height and area increases in accordance
with Sections 504 and 506 for such accessory
occupancies.

Separation. No separation is required
between accessory occupancies or the main occupancy.
Exception: Group H-2, H-3, H-4 or H-5 occupancies
shall be separated from all other occupancies in accordance
with Section 508.3.3.

Nonseparated occupancies. Buildings or portions
of buildings that comply with the provisions of this section
shall qualify as nonseparated occupancies.

Occupancy classification. Nonseparated
occupancies shall be individually classified in accordance
with Section 302.1. Code requirements shall apply

REQUIRED SEPARATION OF OCCUPANCIES (HOURS)

Allowable area and height. The allowable
area and height of the building or portion thereof shall be
based on the most restrictive allowances for the occupancy
groups under consideration for the type of construction
of the building in accordance with Section
503.1.

Separation. No separation is required
between occupancies.
Exception: Group H-2, H-3, H-4 or H-5 occupancies
shall be separated from all other occupancies in accordance
with Section 508.3.3.

Separated occupancies. Buildings or portions of
buildings that comply with the provisions of this section
shall qualify as separated occupancies.

Occupancy classification. Separated occupancies
shall be individually classified in accordance
with Section 302.1. Each fire area shall comply with this
code based on the occupancy classification of that portion
of the building.

Allowable area. In each story, the building
area shall be such that the sum of the ratios of the actual
floor area of each occupancy divided by the allowable
area of each occupancy shall not exceed one.

Allowable height. Each occupancy shall comply
with the height limitations based on the type of construction
of the building in accordance with Section
503.1. The height, in both feet and stories, of each fire
area shall be measured from grade plane. This measurement
shall include the height, in both feet and stories, of
intervening fire areas.
Exception: Special provisions permitted by Section
509.

Separation. Individual occupancies shall be
separated from adjacent occupancies in accordance with
Table 508.3.3

Construction. Required separations
shall be fire barriers constructed in accordance with
Section 706 or horizontal assemblies constructed in
accordance with Section 711, or both, so as to completely
separate adjacent occupancies.

International Building Code 508.3.1

Accessory occupancies. Accessory occupancies
are those occupancies subsidiary to the main occupancy of
the building or portion thereof. Aggregate accessory occupancies
shall not occupy more than 10 percent of the area of
the story in which they are located and shall not exceed the
tabular values in Table 503, without height and area
increases in accordance with Sections 504 and 506 for such
accessory occupancies.
Exceptions:
1. Accessory assembly areas having a floor area less
than 750 square feet (69.7 m2) are not considered
separate occupancies.
2. Assembly areas that are accessory to Group E
occupancies are not considered separate occupancies
except when applying the assembly occupancy
requirements of Chapter 11.
3. Accessory religious educational rooms and religious
auditoriums with occupant loads of less than
100 are not considered separate occupancies.

Occupancy classification. Accessory occupancies
shall be individually classified in accordance
with Section 302.1. Code requirements shall apply to
each portion of the building based on the occupancy classification
of that accessory space, except that the most
restrictive applicable provisions of Section 403 and
Chapter 9 shall apply to the entire building or portion
thereof.

Allowable area and height. The allowable
area and height of the building shall be based on the
allowable area and height for the main occupancy in
accordance with Section 503.1. The height of any accessory
occupancy shall not exceed the tabular values in
Table 503, without height and area increases in accordance
with Sections 504 and 506 for such accessory
occupancies.

Separation. No separation is required
between accessory occupancies or the main occupancy.
Exception: Group H-2, H-3, H-4 or H-5 occupancies
shall be separated from all other occupancies in accordance
with Section 508.3.3.

International Building Code 508.3.1.1

Occupancy classification. Accessory occupancies
shall be individually classified in accordance
with Section 302.1. Code requirements shall apply to
each portion of the building based on the occupancy classification
of that accessory space, except that the most
restrictive applicable provisions of Section 403 and
Chapter 9 shall apply to the entire building or portion
thereof.

International Building Code 508.3.1.2

Allowable area and height. The allowable
area and height of the building shall be based on the
allowable area and height for the main occupancy in
accordance with Section 503.1. The height of any accessory
occupancy shall not exceed the tabular values in
Table 503, without height and area increases in accordance
with Sections 504 and 506 for such accessory
occupancies.

International Building Code 508.3.1.3

Separation. No separation is required
between accessory occupancies or the main occupancy.
Exception: Group H-2, H-3, H-4 or H-5 occupancies
shall be separated from all other occupancies in accordance
with Section 508.3.3.

International Building Code 508.3.2

Nonseparated occupancies. Buildings or portions
of buildings that comply with the provisions of this section
shall qualify as nonseparated occupancies.

Occupancy classification. Nonseparated
occupancies shall be individually classified in accordance
with Section 302.1. Code requirements shall apply

Allowable area and height. The allowable
area and height of the building or portion thereof shall be
based on the most restrictive allowances for the occupancy
groups under consideration for the type of construction
of the building in accordance with Section
503.1.

Separation. No separation is required
between occupancies.
Exception: Group H-2, H-3, H-4 or H-5 occupancies
shall be separated from all other occupancies in accordance
with Section 508.3.3.

Separated occupancies. Buildings or portions of
buildings that comply with the provisions of this section
shall qualify as separated occupancies.

Occupancy classification. Separated occupancies
shall be individually classified in accordance
with Section 302.1. Each fire area shall comply with this
code based on the occupancy classification of that portion
of the building.

Allowable area. In each story, the building
area shall be such that the sum of the ratios of the actual
floor area of each occupancy divided by the allowable
area of each occupancy shall not exceed one.

Allowable height. Each occupancy shall comply
with the height limitations based on the type of construction
of the building in accordance with Section
503.1. The height, in both feet and stories, of each fire
area shall be measured from grade plane. This measurement
shall include the height, in both feet and stories, of
intervening fire areas.
Exception: Special provisions permitted by Section
509.

Separation. Individual occupancies shall be
separated from adjacent occupancies in accordance with
Table 508.3.3

Construction. Required separations
shall be fire barriers constructed in accordance with
Section 706 or horizontal assemblies constructed in
accordance with Section 711, or both, so as to completely
separate adjacent occupancies.

International Building Code 508.3.2.1

Occupancy classification. Nonseparated
occupancies shall be individually classified in accordance
with Section 302.1. Code requirements shall apply
Allowable area and height. The allowablearea and height

of the building or portion thereof shall bebased on the

most restrictive allowances for the occupancygroups under

consideration for the type of constructionof the building in accordance with Section503.1.

Separation. No separation is required
between occupancies.
Exception: Group H-2, H-3, H-4 or H-5 occupancies
shall be separated from all other occupancies in accordance
with Section 508.3.3.

Separated occupancies. Buildings or portions of
buildings that comply with the provisions of this section
shall qualify as separated occupancies.

Occupancy classification. Separated occupancies
shall be individually classified in accordance
with Section 302.1. Each fire area shall comply with this
code based on the occupancy classification of that portion
of the building.

Allowable area. In each story, the building
area shall be such that the sum of the ratios of the actual
floor area of each occupancy divided by the allowable
area of each occupancy shall not exceed one.

Allowable height. Each occupancy shall comply
with the height limitations based on the type of construction
of the building in accordance with Section
503.1. The height, in both feet and stories, of each fire
area shall be measured from grade plane. This measurement
shall include the height, in both feet and stories, of
intervening fire areas.
Exception: Special provisions permitted by Section
509.

Separation. Individual occupancies shall be
separated from adjacent occupancies in accordance with
Table 508.3.3

Construction. Required separations
shall be fire barriers constructed in accordance with
Section 706 or horizontal assemblies constructed in
accordance with Section 711, or both, so as to completely
separate adjacent occupancies.

International Building Code 508.3.2.2

Allowable area and height. The allowable
area and height of the building or portion thereof shall be
based on the most restrictive allowances for the occupancy
groups under consideration for the type of construction
of the building in accordance with Section
503.1.

Separation. No separation is required
between occupancies.
Exception: Group H-2, H-3, H-4 or H-5 occupancies
shall be separated from all other occupancies in accordance
with Section 508.3.3.

International Building Code 508.3.2.3

Separation. No separation is required
between occupancies.
Exception: Group H-2, H-3, H-4 or H-5 occupancies
shall be separated from all other occupancies in accordance
with Section 508.3.3.

International Building Code 508.3.3

Separated occupancies. Buildings or portions of
buildings that comply with the provisions of this section
shall qualify as separated occupancies.

Occupancy classification. Separated occupancies
shall be individually classified in accordance
with Section 302.1. Each fire area shall comply with this
code based on the occupancy classification of that portion
of the building.

Allowable area. In each story, the building
area shall be such that the sum of the ratios of the actual
floor area of each occupancy divided by the allowable
area of each occupancy shall not exceed one.

Allowable height. Each occupancy shall comply
with the height limitations based on the type of construction
of the building in accordance with Section
503.1. The height, in both feet and stories, of each fire
area shall be measured from grade plane. This measurement
shall include the height, in both feet and stories, of
intervening fire areas.
Exception: Special provisions permitted by Section
509.

Separation. Individual occupancies shall be
separated from adjacent occupancies in accordance with
Table 508.3.3

Construction. Required separations
shall be fire barriers constructed in accordance with
Section 706 or horizontal assemblies constructed in
accordance with Section 711, or both, so as to completely
separate adjacent occupancies.

International Building Code 508.3.3.1

Occupancy classification. Separated occupancies
shall be individually classified in accordance
with Section 302.1. Each fire area shall comply with this
code based on the occupancy classification of that portion
of the building.

International Building Code 508.3.3.2

Allowable area. In each story, the building
area shall be such that the sum of the ratios of the actual
floor area of each occupancy divided by the allowable
area of each occupancy shall not exceed one.

International Building Code 508.3.3.3

Allowable height. Each occupancy shall comply
with the height limitations based on the type of construction
of the building in accordance with Section
503.1. The height, in both feet and stories, of each fire
area shall be measured from grade plane. This measurement
shall include the height, in both feet and stories, of
intervening fire areas.
Exception: Special provisions permitted by Section
509.

Separation. Individual occupancies shall be
separated from adjacent occupancies in accordance with
Table 508.3.3

Construction. Required separations
shall be fire barriers constructed in accordance with
Section 706 or horizontal assemblies constructed in
accordance with Section 711, or both, so as to completely
separate adjacent occupancies.

International Building Code 508.3.3.4

Separation. Individual occupancies shall be
separated from adjacent occupancies in accordance with
Table 508.3.3

Construction. Required separations
shall be fire barriers constructed in accordance with
Section 706 or horizontal assemblies constructed in
accordance with Section 711, or both, so as to completely
separate adjacent occupancies.

International Building Code 508.3.3.4.1

Construction. Required separations
shall be fire barriers constructed in accordance with
Section 706 or horizontal assemblies constructed in
accordance with Section 711, or both, so as to completely
separate adjacent occupancies.

International Building Code Section 508.2.3

Protection. Where an automatic fire-extinguishing
system or an automatic sprinkler system is provided in
accordance with Table 508.2, only the incidental use areas
need be equipped with such a system.

International Building Code TABLE 508.2

INCIDENTAL USE AREAS

International Building Code TABLE 508.3.3

REQUIRED SEPARATION OF OCCUPANCIES (HOURS)