International Building Code Section 1509

International Building Code 1509.1

General. The provisions of this section shall govern the
construction of rooftop structures.

International Building Code 1509.2

Penthouses. A penthouse or other projection above the
roof in structures of other than Type I construction shall not
exceed 28 feet (8534 mm) above the roof where used as an
enclosure for tanks or for elevators that run to the roof and in all
other cases shall not extend more than 18 feet (5486 mm) above
the roof. The aggregate area of penthouses and other rooftop
structures shall not exceed one-third the area of the supporting
roof. A penthouse, bulkhead or any other similar projection
above the roof shall not be used for purposes other than shelter
of mechanical equipment or shelter of vertical shaft openings
in the roof. Provisions such as louvers, louver blades or flashing
shall be made to protect the mechanical equipment and the
building interior from the elements. Penthouses or bulkheads
used for purposes other than permitted by this section shall
conform to the requirements of this code for an additional
story. The restrictions of this section shall not prohibit the placing
of wood flagpoles or similar structures on the roof of any
building.

Type of construction. Penthouses shall be constructed
withwalls, floors and roof as required for the building.
Exceptions:
1. On buildings of Type I and II construction, the
exterior walls and roofs of penthouses with a fire
separation distance of more than 5 feet (1524 mm)
and less than 20 feet (6096 mm) shall be of at least
1-hour fire-resistance-rated noncombustible construction.
Walls and roofs with a fire separation
distance of 20 feet (6096 mm) or greater shall be of
noncombustible construction. Interior framing
and walls shall be of noncombustible construction.
2. On buildings of Type III, IV and V construction,
the exterior walls of penthouses with a fire separation
distance of more than 5 feet (1524 mm) and
less than 20 feet (6096 mm) shall be at least 1-hour
fire-resistance-rated construction. Walls with a
fire separation distance of 20 feet (6096 mm) or
greater from a common property line shall be of
Type IV or noncombustible construction. Roofs
shall be constructed of materials and fire-resistance
rated as required in Table 601. Interior framing
and walls shall be Type IV or noncombustible
construction.
3. Unprotected noncombustible enclosures housing
only mechanical equipment and located with a
minimum fire separation distance of 20 feet (6096
mm) shall be permitted.
4. On one-story buildings, combustible unroofed
mechanical equipment screens, fences or similar
enclosures are permitted where located with a fire
separation distance of at least 20 feet (6096 mm)
from adjacent property lines and where not
exceeding 4 feet (1219 mm) in height above the
roof surface.
5. Dormers shall be of the same type of construction
as the roof on which they are placed, or of the exterior
walls of the building.

International Building Code 1509.2.1

International Building Code 1509.3

Tanks. Tanks having a capacity of more than 500 gallons
(2 m3) placed in or on a building shall be supported on
masonry, reinforced concrete, steel or Type IV construction
provided that, where such supports are located in the building
above the lowest story, the support shall be fire-resistance rated
as required for Type IA construction.

Valve. Such tanks shall have in the bottom or on
the side near the bottom, a pipe or outlet, fitted with a suitable
quick opening valve for discharging the contents in an
emergency through an adequate drain.

Location. Such tanks shall not be placed over or
near a line of stairs or an elevator shaft, unless there is a solid
roof or floor underneath the tank.

Tank cover. Unenclosed roof tanks shall have covers
sloping toward the outer edges.

International Building Code 1509.3.1

International Building Code 1509.3.2

Location. Such tanks shall not be placed over or
near a line of stairs or an elevator shaft, unless there is a solid
roof or floor underneath the tank.

International Building Code 1509.3.3

Tank cover. Unenclosed roof tanks shall have covers
sloping toward the outer edges.

International Building Code 1509.4

Cooling towers. Cooling towers in excess of 250
square feet (23.2 m2) in base area or in excess of 15 feet (4572
mm) high where located on building roofs more than 50 feet
(15 240 mm) high shall be of noncombustible construction.
Cooling towers shall not exceed one-third of the supporting
roof area.
Exception: Drip boards and the enclosing construction of
wood not less than 1 inch (25 mm) nominal thickness, provided
the wood is covered on the exterior of the tower with
noncombustible material.

International Building Code 1509.5

Towers, spires, domes and cupolas. Any tower, spire,
dome or cupola shall be of a type of construction not less in
fire-resistance rating than required for the building to which it
is attached, except that any such tower, spire, dome or cupola
that exceeds 85 feet (25 908 mm) in height above grade plane,
exceeds 200 square feet (18.6 m2) in horizontal area or is used
for any purpose other than a belfry or an architectural embellishment
shall be constructed of and supported on Type I or II
construction.
2006 INTERNATIONAL BUILDING CODE 275
ROOF ASSEMBLIES AND ROOFTOP STRUCTURES

Noncombustible construction required. Any
tower, spire, dome or cupola that exceeds 60 feet (18 288) in
height above the highest point at which it comes in contact
with the roof, or that exceeds 200 square feet (18.6 m2) in
area at any horizontal section, or which is intended to be
used for any purpose other than a belfry or architectural
embellishment, shall be entirely constructed of and supported
by noncombustible materials. Such structures shall
be separated from the building below by construction having
a fire-resistance rating of not less than 1.5 hours with
openings protected with a minimum 1.5-hour fire-protection
rating. Structures, except aerial supports 12 feet (3658
mm) high or less, flagpoles,water tanks and cooling towers,
placed above the roof of any building more than 50 feet (15
240 mm) in height, shall be of noncombustible material and
shall be supported by construction of noncombustible material.

Towers and spires. Towers and spires where
enclosed shall have exterior walls as required for the building
to which they are attached. The roof covering of spires
shall be of a class of roof covering as required for the main
roof of the rest of the structure.