Section 1609.1/Wind Loads
IBC 1609 establishes wind load design requirements including basic wind speed, exposure category, and reference to ASCE 7 for calculation procedures.
All buildings and structures must be designed and constructed to resist wind loads as determined by ASCE 7 Chapters 26 through 31. Section 1609.1.1 requires the basic wind speed to be determined from the ASCE 7 wind speed maps based on the building's Risk Category. The exposure category (B, C, or D) is determined by the surface roughness of the surrounding terrain per ASCE 7 Section 26.7. Section 1609.1.2 requires buildings in wind-borne debris regions (wind speeds of 130 mph or greater in hurricane-prone areas, or within one mile of the coast where wind speeds are 110 mph or greater) to have impact-resistant glazing or shutters tested per ASTM E1996 and E1886. The structural general notes must include the basic wind speed, risk category, exposure category, and the applicable ASCE 7 edition.
Why this section exists
Wind is the governing lateral load for most low-rise and mid-rise buildings outside of high seismic regions. The IBC references ASCE 7 for wind load calculation procedures, which determine both the main wind-force resisting system (MWFRS) pressures for the overall structure and the component and cladding (C&C) pressures for individual elements. The wind-borne debris requirements protect building envelopes in hurricane zones from flying debris that can breach glazing, allowing wind-driven rain and internal pressurization that lead to roof failures. The exposure category significantly affects design pressures: a building in Exposure D (flat, unobstructed coastal terrain) can experience 50% higher pressures than the same building in Exposure B (suburban terrain).
What plan reviewers look for
Plan reviewers check the structural general notes for the basic wind speed (must match the ASCE 7 map for the building's location and risk category), exposure category (with justification for the selected category), and the ASCE 7 edition used. They verify that the MWFRS wind pressures and C&C pressures are calculated and applied correctly. For buildings in wind-borne debris regions, they check that impact- resistant glazing or shutters are specified on the window and door schedules with the applicable ASTM E1996 missile level.