International Building Code Section 1609


International Building Code 1609.1

Applications. Buildings, structures and parts thereof
shall be designed to withstand the minimum wind loads prescribed
herein. Decreases in wind loads shall not be made for
the effect of shielding by other structures.
2006 INTERNATIONAL BUILDING CODE 289
STRUCTURAL DESIGN

Determination of wind loads. Wind loads on
every building or structure shall be determined in accordance
with Chapter 6 of ASCE 7. The type of opening protection
required, the basic wind speed and the exposure
category for a site is permitted to be determined in accordance
with Section 1609 or ASCE 7.Wind shall be assumed
to come from any horizontal direction and wind pressures
shall be assumed to act normal to the surface considered.
Exceptions:
1. Subject to the limitations of Section 1609.1.1.1,
the provisions of SBCCI SSTD 10 shall be permitted
for applicable Group R-2 and R-3 buildings.
2. Subject to the limitations of Section 1609.1.1.1,
residential structures using the provisions of the
AF&PA WFCM.
3. Designs using NAAMM FP 1001.
4. Designs using TIA/EIA-222 for antenna-supporting
structures and antennas.

Applicability. The provisions of SSTD 10
are applicable only to buildings located within Exposure
B or C as defined in Section 1609.4. The provisions of
SBCCI SSTD 10 and the AF&PAWFCMshall not apply
to buildings sited on the upper half of an isolated hill,
ridge or escarpment meeting the following conditions:
1. The hill, ridge or escarpment is 60 feet (18 288
mm) or higher if located in Exposure B or 30 feet
(9144 mm) or higher if located in Exposure C;
2. The maximum average slope of the hill exceeds 10
percent; and
3. The hill, ridge or escarpment is unobstructed
upwind by other such topographic features for a distance
from the high point of 50 times the height of
the hill or 1 mile (1.61 km), whichever is greater.

Protection of openings. In wind-borne debris
regions, glazing in buildings shall be impact-resistant or
protected with an impact-resistant covering meeting the
requirements of an approved impact-resisting standard or
ASTM E 1996 and ASTM E 1886 referenced therein as follows:
1. Glazed openings located within 30 feet (9144 mm) of
grade shall meet the requirements of the Large Missile
Test of ASTM E 1996.
2. Glazed openings located more than 30 feet (9144
mm) above grade shall meet the provisions of the
Small Missile Test of ASTM E 1996.
Exceptions:
1. Wood structural panels with a minimum thickness
of 7/16 inch (11.1 mm) and maximum panel span of
8 feet (2438 mm) shall be permitted for opening
protection in one- and two-story buildings. Panels
shall be precut so that they shall be attached to the
framing surrounding the opening containing the
product with the glazed opening. Panels shall be
secured with the attachment hardware provided.
Attachments shall be designed to resist the components
and cladding loads determined in accordance
with the provisions of ASCE 7. Attachment
in accordance with Table 1609.1.2 is permitted for
buildings with a mean roof height of 33 feet (10
058 mm) or less where wind speeds do not exceed
130 mph (57.2 m/s).
2. Glazing in Occupancy Category I buildings as
defined in Section 1604.5, including greenhouses
that are occupied for growing plants on a production
or research basis, without public access shall
be permitted to be unprotected.
3. Glazing in Occupancy Category II, III or IV buildings
located over 60 feet (18 288 mm) above the
ground and over 30 feet (9144 mm) above aggregate
surface roofs located within 1,500 feet (458
m) of the building shall be permitted to be unprotected.

Louvers. Louvers protecting intake and
exhaust ventilation ducts not assumed to be open that are
located within 30 feet (9144 mm) of grade shall meet
requirements of an approved impact-resisting standard
or the Large Missile Test of ASTM E 1996.

International Building Code 1609.1.1

Determination of wind loads. Wind loads on
every building or structure shall be determined in accordance
with Chapter 6 of ASCE 7. The type of opening protection
required, the basic wind speed and the exposure
category for a site is permitted to be determined in accordance
with Section 1609 or ASCE 7.Wind shall be assumed
to come from any horizontal direction and wind pressures
shall be assumed to act normal to the surface considered.
Exceptions:
1. Subject to the limitations of Section 1609.1.1.1,
the provisions of SBCCI SSTD 10 shall be permitted
for applicable Group R-2 and R-3 buildings.
2. Subject to the limitations of Section 1609.1.1.1,
residential structures using the provisions of the
AF&PA WFCM.
3. Designs using NAAMM FP 1001.
4. Designs using TIA/EIA-222 for antenna-supporting
structures and antennas.

Applicability. The provisions of SSTD 10
are applicable only to buildings located within Exposure
B or C as defined in Section 1609.4. The provisions of
SBCCI SSTD 10 and the AF&PAWFCMshall not apply
to buildings sited on the upper half of an isolated hill,
ridge or escarpment meeting the following conditions:
1. The hill, ridge or escarpment is 60 feet (18 288
mm) or higher if located in Exposure B or 30 feet
(9144 mm) or higher if located in Exposure C;
2. The maximum average slope of the hill exceeds 10
percent; and
3. The hill, ridge or escarpment is unobstructed
upwind by other such topographic features for a distance
from the high point of 50 times the height of
the hill or 1 mile (1.61 km), whichever is greater.

International Building Code 1609.1.1.1

Applicability. The provisions of SSTD 10
are applicable only to buildings located within Exposure
B or C as defined in Section 1609.4. The provisions of
SBCCI SSTD 10 and the AF&PAWFCMshall not apply
to buildings sited on the upper half of an isolated hill,
ridge or escarpment meeting the following conditions:
1. The hill, ridge or escarpment is 60 feet (18 288
mm) or higher if located in Exposure B or 30 feet
(9144 mm) or higher if located in Exposure C;
2. The maximum average slope of the hill exceeds 10
percent; and
3. The hill, ridge or escarpment is unobstructed
upwind by other such topographic features for a distance
from the high point of 50 times the height of
the hill or 1 mile (1.61 km), whichever is greater.

International Building Code 1609.1.2

Protection of openings. In wind-borne debris
regions, glazing in buildings shall be impact-resistant or
protected with an impact-resistant covering meeting the
requirements of an approved impact-resisting standard or
ASTM E 1996 and ASTM E 1886 referenced therein as follows:
1. Glazed openings located within 30 feet (9144 mm) of
grade shall meet the requirements of the Large Missile
Test of ASTM E 1996.
2. Glazed openings located more than 30 feet (9144
mm) above grade shall meet the provisions of the
Small Missile Test of ASTM E 1996.
Exceptions:
1. Wood structural panels with a minimum thickness
of 7/16 inch (11.1 mm) and maximum panel span of
8 feet (2438 mm) shall be permitted for opening
protection in one- and two-story buildings. Panels
shall be precut so that they shall be attached to the
framing surrounding the opening containing the
product with the glazed opening. Panels shall be
secured with the attachment hardware provided.
Attachments shall be designed to resist the components
and cladding loads determined in accordance
with the provisions of ASCE 7. Attachment
in accordance with Table 1609.1.2 is permitted for
buildings with a mean roof height of 33 feet (10
058 mm) or less where wind speeds do not exceed
130 mph (57.2 m/s).
2. Glazing in Occupancy Category I buildings as
defined in Section 1604.5, including greenhouses
that are occupied for growing plants on a production
or research basis, without public access shall
be permitted to be unprotected.
3. Glazing in Occupancy Category II, III or IV buildings
located over 60 feet (18 288 mm) above the
ground and over 30 feet (9144 mm) above aggregate
surface roofs located within 1,500 feet (458
m) of the building shall be permitted to be unprotected.

Louvers. Louvers protecting intake and
exhaust ventilation ducts not assumed to be open that are
located within 30 feet (9144 mm) of grade shall meet
requirements of an approved impact-resisting standard
or the Large Missile Test of ASTM E 1996.

International Building Code 1609.1.2.1

Louvers. Louvers protecting intake and
exhaust ventilation ducts not assumed to be open that are
located within 30 feet (9144 mm) of grade shall meet
requirements of an approved impact-resisting standard
or the Large Missile Test of ASTM E 1996.

International Building Code 1609.2

Definitions. The following words and terms shall, for
the purposes of Section 1609, have the meanings shown herein.
HURRICANE-PRONE REGIONS. Areas vulnerable to
hurricanes defined as:
1. The U. S. Atlantic Ocean and Gulf of Mexico coasts
where the basic wind speed is greater than 90 mph (40
m/s) and
2. Hawaii, Puerto Rico, Guam, Virgin Islands and American
Samoa.
WIND-BORNE DEBRIS REGION. Portions of hurricane-
prone regions that are within 1 mile (1.61 km) of the
coastal mean high water line where the basic wind speed is 110
mph (48 m/s) or greater; or portions of hurricane-prone regions
292 2006 INTERNATIONAL BUILDING CODE
STRUCTURAL DESIGN
?
?
?
?
?
where the basic wind speed is 120 mph (53 m/s) or greater; or
Hawaii.

International Building Code 1609.3

Basic wind speed. The basic wind speed, in mph, for
the determination of the wind loads shall be determined by Figure
1609. Basic wind speed for the special wind regions indicated,
near mountainous terrain and near gorges shall be in
accordance with local jurisdiction requirements. Basic wind
speeds determined by the local jurisdiction shall be in accordance
with Section 6.5.4 of ASCE 7.
In nonhurricane-prone regions, when the basic wind speed is
estimated from regional climatic data, the basic wind speed
shall be not less than the wind speed associated with an annual
probability of 0.02 (50-year mean recurrence interval), and the
estimate shall be adjusted for equivalence to a 3-second gust
wind speed at 33 feet (10 m) above ground in Exposure Category
C. The data analysis shall be performed in accordance
with Section 6.5.4.2 of ASCE 7.

Wind speed conversion. When required, the
3-second gust basic wind speeds of Figure 1609 shall be
converted to fastest-mile wind speeds, Vfm, using Table
1609.3.1 or Equation 16-34.

International Building Code 1609.3.1

Wind speed conversion. When required, the
3-second gust basic wind speeds of Figure 1609 shall be
converted to fastest-mile wind speeds, Vfm, using Table
1609.3.1 or Equation 16-34.

International Building Code 1609.4

Exposure category. For each wind direction considered,
an exposure category that adequately reflects the characteristics
of ground surface irregularities shall be determined for
the site at which the building or structure is to be constructed.
Account shall be taken of variations in ground surface roughness
that arise from natural topography and vegetation as well
as from constructed features.

Wind directions and sectors. For each selected
wind direction at which the wind loads are to be evaluated,
the exposure of the building or structure shall be determined
for the two upwind sectors extending 45 degrees (0.79 rad)
either side of the selected wind direction. The exposures in
these two sectors shall be determined in accordance with
Sections 1609.4.2 and 1609.4.3 and the exposure resulting
in the highest wind loads shall be used to represent winds
from that direction.

Surface roughness categories. A ground surface
roughness within each 45-degree (0.79 rad) sector shall be
determined for a distance upwind of the site as defined in
Section 1609.4.3 from the categories defined below, for the
purpose of assigning an exposure category as defined in
Section 1609.4.3.
Surface Roughness B. Urban and suburban areas,
wooded areas or other terrain with numerous closely
spaced obstructions having the size of single-family
dwellings or larger.
Surface Roughness C. Open terrain with scattered
obstructions having heights generally less than 30 feet
(9144 mm). This category includes flat open country,
grasslands, and all water surfaces in hurricane-prone
regions.
Surface Roughness D. Flat, unobstructed areas and
water surfaces outside hurricane-prone regions. This category
includes smooth mud flats, salt flats and unbroken
ice.

Exposure categories. An exposure category shall
be determined in accordance with the following:
Exposure B. Exposure B shall apply where the ground
surface roughness condition, as defined by Surface
Roughness B, prevails in the upwind direction for a distance
of at least 2,600 feet (792 m) or 20 times the height
of the building, whichever is greater.
Exception: For buildings whose mean roof height is
less than or equal to 30 feet (9144 mm), the upwind distance
is permitted to be reduced to 1,500 feet (457 m).
Exposure C. Exposure C shall apply for all cases where
Exposures B or D do not apply.
Exposure D. Exposure D shall apply where the ground
surface roughness, as defined by Surface Roughness D,
prevails in the upwind direction for a distance of at least
5,000 feet (1524 m) or 20 times the height of the building,
whichever is greater. ExposureDshall extend inland
from the shoreline for a distance of 600 feet (183 m) or 20
times the height of the building, whichever is greater.

International Building Code 1609.4.1

Wind directions and sectors. For each selected
wind direction at which the wind loads are to be evaluated,
the exposure of the building or structure shall be determined
for the two upwind sectors extending 45 degrees (0.79 rad)
either side of the selected wind direction. The exposures in
these two sectors shall be determined in accordance with
Sections 1609.4.2 and 1609.4.3 and the exposure resulting
in the highest wind loads shall be used to represent winds
from that direction.

International Building Code 1609.4.2

Surface roughness categories. A ground surface
roughness within each 45-degree (0.79 rad) sector shall be
determined for a distance upwind of the site as defined in
Section 1609.4.3 from the categories defined below, for the
purpose of assigning an exposure category as defined in
Section 1609.4.3.
Surface Roughness B. Urban and suburban areas,
wooded areas or other terrain with numerous closely
spaced obstructions having the size of single-family
dwellings or larger.
Surface Roughness C. Open terrain with scattered
obstructions having heights generally less than 30 feet
(9144 mm). This category includes flat open country,
grasslands, and all water surfaces in hurricane-prone
regions.
Surface Roughness D. Flat, unobstructed areas and
water surfaces outside hurricane-prone regions. This category
includes smooth mud flats, salt flats and unbroken
ice.

International Building Code 1609.4.3

Exposure categories. An exposure category shall
be determined in accordance with the following:
Exposure B. Exposure B shall apply where the ground
surface roughness condition, as defined by Surface
Roughness B, prevails in the upwind direction for a distance
of at least 2,600 feet (792 m) or 20 times the height
of the building, whichever is greater.
Exception: For buildings whose mean roof height is
less than or equal to 30 feet (9144 mm), the upwind distance
is permitted to be reduced to 1,500 feet (457 m).
Exposure C. Exposure C shall apply for all cases where
Exposures B or D do not apply.
Exposure D. Exposure D shall apply where the ground
surface roughness, as defined by Surface Roughness D,
prevails in the upwind direction for a distance of at least
5,000 feet (1524 m) or 20 times the height of the building,
whichever is greater. ExposureDshall extend inland
from the shoreline for a distance of 600 feet (183 m) or 20
times the height of the building, whichever is greater.

International Building Code 1609.5

Roof systems.

Roof deck. The roof deck shall be designed to
withstand the wind pressures determined in accordance
with ASCE 7.
2006 INTERNATIONAL BUILDING CODE 293
STRUCTURAL DESIGN

Roof coverings. Roof coverings shall comply
with Section 1609.5.1.
Exception: Rigid tile roof coverings that are air permeable
and installed over a roof deck complying with Section
1609.5.1 are permitted to be designed in accordance
with Section 1609.5.3.
Asphalt shingles installed over a roof deck complying
with Section 1609.5.1 shall be tested to determine the resistance
of the sealant to uplift forces using ASTM D 6381.
Asphalt shingles installed over a roof deck complying
with Section 1609.5.1 are permitted to be designed using
UL 2390 to determine appropriate uplift and force coefficients
applied to the shingle.

Rigid tile. Wind loads on rigid tile roof coverings
shall be determined in accordance with the following equation:
Ma =
Concrete and clay roof tiles complying with the following
limitations shall be designed to withstand the aerodynamic
uplift moment as determined by this section.
1. The roof tiles shall be either loose laid on battens,
mechanically fastened, mortar set or adhesive set.
2. The roof tiles shall be installed on solid sheathing
which has been designed as components and cladding.
3. An underlayment shall be installed in accordance
with Chapter 15.
4. The tile shall be single lapped interlocking with a
minimum head lap of not less than 2 inches (51
mm).
5. The length of the tile shall be between 1.0 and 1.75
feet (305 mm and 533 mm).
6. The exposed width of the tile shall be between 0.67
and 1.25 feet (204 mm and 381 mm).
7. The maximum thickness of the tail of the tile shall not
exceed 1.3 inches (33 mm).
8. Roof tiles using mortar set or adhesive set systems
shall have at least two-thirds of the tile’s area free of
mortar or adhesive contact.

International Building Code 1609.5.1

Roof deck. The roof deck shall be designed to
withstand the wind pressures determined in accordance
with ASCE 7.
2006 INTERNATIONAL BUILDING CODE 293
STRUCTURAL DESIGN

International Building Code 1609.5.2

Roof coverings. Roof coverings shall comply
with Section 1609.5.1.
Exception: Rigid tile roof coverings that are air permeable
and installed over a roof deck complying with Section
1609.5.1 are permitted to be designed in accordance
with Section 1609.5.3.
Asphalt shingles installed over a roof deck complying
with Section 1609.5.1 shall be tested to determine the resistance
of the sealant to uplift forces using ASTM D 6381.
Asphalt shingles installed over a roof deck complying
with Section 1609.5.1 are permitted to be designed using
UL 2390 to determine appropriate uplift and force coefficients
applied to the shingle.

International Building Code 1609.5.3

Rigid tile. Wind loads on rigid tile roof coverings
shall be determined in accordance with the following equation:
Ma =
Concrete and clay roof tiles complying with the following
limitations shall be designed to withstand the aerodynamic
uplift moment as determined by this section.
1. The roof tiles shall be either loose laid on battens,
mechanically fastened, mortar set or adhesive set.
2. The roof tiles shall be installed on solid sheathing
which has been designed as components and cladding.
3. An underlayment shall be installed in accordance
with Chapter 15.
4. The tile shall be single lapped interlocking with a
minimum head lap of not less than 2 inches (51
mm).
5. The length of the tile shall be between 1.0 and 1.75
feet (305 mm and 533 mm).
6. The exposed width of the tile shall be between 0.67
and 1.25 feet (204 mm and 381 mm).
7. The maximum thickness of the tail of the tile shall not
exceed 1.3 inches (33 mm).
8. Roof tiles using mortar set or adhesive set systems
shall have at least two-thirds of the tile’s area free of
mortar or adhesive contact.