Virginia Law

A. Add the following notation to the list of notations in Section 1602.1 (all other notations remain):

V_T = Tornado speed, miles per hour (mph) (m/s) determined from Chapter 32 of ASCE 7.

B. Change Section 1603.1.4 of the IBC to read:

1603.1.4 Wind and tornado design data. The following information related to wind loads and, where required by Section 1609.5 tornado loads, shall be shown regardless of whether wind loads govern the design of the lateral force-resisting system of the structure:

1. Basic wind speed, V (mph), tornado speed, V_T, and allowable stress design wind speed, V_asd, as determined in accordance with Section 1609.3.1.

2. Risk category.

3. Effective plan area, A_e for tornado design in accordance with Chapter 32 of ASCE 7.

4. Wind exposure. Applicable wind direction if more than one wind exposure is utilized.

5. Applicable internal pressure coefficients and applicable tornado internal pressure coefficients.

6. Design wind pressures and their applicable zones with dimensions to be used for exterior component and cladding materials not specifically designed by the registered design professional responsible for the design of the structure, pounds per square foot (kN/m²). Where design for tornado loads is required, the design pressures shown shall be the maximum of wind or tornado pressures.

C. Add Exception 4 to Section 1605.1 of the IBC to read:

4. Where design for tornado loads is required, the alternative allowable stress design load combinations of Section 1605.2 shall not apply when tornado loads govern the design.

D. Change Sections 1607.14 and 1607.14.3 of the IBC to read:

1607.14 Roof loads. The structural supports of roofs and marquees shall be designed to resist wind and, where applicable, tornado, snow, and earthquake loads, in addition to the dead load of construction and the appropriate live loads as prescribed in this section or as set forth in Table 1607.1. The live loads acting on a sloping surface shall be assumed to act vertically on the horizontal projection of that surface.

1607.14.3 Awnings and canopies. Awnings and canopies shall be designed for uniform live loads as required in Table 1607.1 as well as for snow loads and wind and tornado loads as specified in Sections 1608 and 1609.

E. Change Section 1609.3 of the IBC to read:

1609.3 Basic wind speed. The basic design wind speed, V, in miles per hour (mph), for the determination of the wind loads shall be determined by Figures 1609.3(1), 1609.3(2), 1609.3(3), and 1609.3(4). The basic design wind speed, V, for use in the design of Risk Category II buildings and structures shall be obtained from Figure 1609.3(1). The basic design wind speed, V, for use in the design of Risk Categories III and IV buildings and structures shall be obtained from Figures 1609.3(2) and 1609.3(3), respectively. The basic design wind speed, V, for use in the design of Risk Category I buildings and structures shall be obtained from Figure 1609.3(4). The basic design wind speeds for localities in special wind regions, near mountainous terrains, and near gorges shall be based on elevation. Areas at 4,000 feet in elevation or higher shall use 142 V mph ( 62.3 m/s) and areas lower than 4,000 feet in elevation shall use 116 V mph ( 52 m/s). Gorge areas shall be based on the highest recorded speed per locality or in accordance with local jurisdiction requirements determined in accordance with Section 26.5.1 of ASCE 7.

In nonhurricane-prone regions, when the basic design wind speed, V, is estimated from regional climatic data, the basic design wind speed, V, shall be determined in accordance with Section 26.5.3 of ASCE 7.

F. Delete Sections 1609.5.1, 1609.5.2, and 1609.5.3 and change Section 1609.5 of the IBC to read:

1609.5 Tornado loads. The design and construction of Risk Category III and IV buildings and other structures located in the tornado-prone region as shown in Figure 1609.5 shall be in accordance with Chapter 32 of ASCE 7, except as modified by this code.

G. Add Figure 1609.5 Tornado-Prone Region to the IBC.

H. Add Sections 1609.6, 1609.6.1, 1609.6.2, 1609.6.3, 1609.6.3.1, and 1609.6.3.2 to the IBC to read:

1609.6 Roof systems. Roof systems shall be designed and constructed in accordance with Sections 1609.6.1 through 1609.6.3, as applicable.

1609.6.1 Roof deck. The roof deck shall be designed to withstand the greater of wind pressures or tornado pressures determined in accordance with ASCE 7.

1609.6.2 Roof coverings. Roof coverings shall comply with Section 1609.6.1.

Exception: Rigid tile roof coverings that are air permeable and installed over a roof deck complying with Section 1609.6.1 are permitted to be designed in accordance with Section 1609.6.3.

Asphalt shingles installed over a roof deck complying with Section 1609.6.1 shall comply with the wind-resistance requirements of Section 1504.2.

1609.6.3 Rigid tile. Wind and tornado loads on rigid tiles shall comply with Section 1609.6.3.1 or 1609.6.3.2, as applicable.

1609.6.3.1 Wind loads. Wind loads on rigid tile roof coverings shall be determined in accordance with the following equation:

(Equation 16-18)

For SI:

where:
b = Exposed width, feet (mm) of the roof tile.

C_L = Lift coefficient. The lift coefficient for concrete and clay tile shall be 0.2 or shall be determined by test in accordance with Section 1504.3.1.

GC_p = Roof pressure coefficient for each applicable roof zone determined from Chapter 30 of ASCE 7. Roof coefficients shall not be adjusted for internal pressure.

L = Length, feet (mm) of the roof tile.

L_a = Moment arm, feet (mm) from the axis of rotation to the point of uplift on the roof tile. The point of uplift shall be taken at 0.76L from the head of the tile and the middle of the exposed width. For roof tiles with nails or screws (with or without a tail clip), the axis of rotation shall be taken as the head of the tile for direct deck application or as the top edge of the batten for battened applications. For roof tiles fastened only by a nail or screw along the side of the tile, the axis of rotation shall be determined by testing. For roof tiles installed with battens and fastened only by a clip near the tail of the tile, the moment arm shall be determined about the top edge of the batten with consideration given for the point of rotation of the tiles based on straight bond or broken bond and the tile profile.

M_a = Aerodynamic uplift moment, feet-pounds (N-mm) acting to raise the tail of the tile.

q_h = Wind velocity pressure, psf (kN/m² ) determined from Section 26.10.2 of ASCE 7.

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 that 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 two 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 not less than two-thirds of the tile's area free of mortar or adhesive contact.

1609.6.3.2 Tornado loads. Tornado loads on rigid tile roof coverings shall be determined in accordance with Section 1609.6.3.1, replacing q_h with q_hT and (GC_P) with K_vT (GC_p) in Equation 16-18, where:

q_hT = tornado velocity pressure, psf (kN/m² ) determined in accordance with Section 32.10 of ASCE 7.

K_vT = tornado pressure coefficient adjustment factor for vertical winds, determined in accordance with Section 32.14 of ASCE 7.

I. Add Section 1612.1.1 to the IBC to read:

1612.1.1 Elevation of manufactured homes. New or replacement manufactured homes to be located in any flood hazard zone shall be placed in accordance with the applicable elevation requirements of this code.

Exception: Manufactured homes installed on sites in an existing manufactured home park or subdivision shall be permitted to be placed so that the manufactured home chassis is supported by reinforced piers or other foundation elements of at least equivalent strength that are no less than 36 inches (914 mm) above grade in lieu of being elevated at or above the base flood elevation, provided no manufactured home at the same site has sustained flood damage exceeding 50% of the market value of the home before the damage occurred.

J. Change Items 1.1 and 2.1 of Section 1612.4 of the IBC to read:

1.1. The elevation of the lowest floor, including the basement, as required by the lowest floor elevation inspection in Section 113.3.2 and for the final inspection in Section 113.3.3.

2.1. The elevation of the bottom of the lowest horizontal structural member as required by the lowest floor elevation inspection in Section 113.3.2 and for the final inspection in Section 113.3.3.