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Home My WebLink AboutBLG_BLD-PEM-002_Wind_Exposure-Plan_RequirementsDEPARTMENT OF PUBLIC WORKS –BUILDING DIVISION COUNTY OF HAWAI'I - 101 Pauahi Street, Suite 7 - Hilo, Hawai‘i 96720 Hilo Office (808) 961-8331 Kona Office (808) 327-3520 Fax (808) 961-8410 Fax (808) 327-3509 The County of Hawai i is an Equal Opportunity Provider and Employer BLD-PEM-002 WIND EXPOSURE – PLAN REQUIREMENTS The purpose of this memo is to outline the correct procedure for determining the wind exposure category for a residential site. The wind exposure category is necessary in order to assess prescriptive bracing when utilizing Table R602.10.3(2) in the 2018 International Residential Code. It must be explicitly identified on the plans. Currently, confusion exists in the County Residential Building Code 5B Section R301.2.1.4 because it states that, “The exposure category shall be determined from Figure R301.2.1.4(a) or using the provisions of ASCE 7-10.” While the latter requires a current, site-specific determination based upon field observation, the former allows for a determination based upon utilizing the referenced Figure which does not reflect current conditions. Commonly, this results in conflicting determinations. The following procedure helps to mitigate the confusion. 1.Applicants are being advised to no longer refer to Figure R301.2.1.4(a) in the County Residential Building Code 5B because it does not account for current, site-specific information upon which each exposure category is based. In general, utilizing the actual field information, in lieu of that shown in the Figure, typically can result in a lower exposure category. 2.Therefore, the exposure category per the County Residential Building Code 5B Section R301.2.1.4 is allowed to be determined utilizing the exposure category descriptions in ASCE 7-10 Section 26.7.3. This Section 26.7.3, summarized, identifies Category B with urban areas, Category C with rural areas, and Category D with locations within 600 feet of the ocean. 3.The site-specific determination of the exposure category is to be performed by the design professional or their deputy and is based upon their personal knowledge and/or observation of the building site. 4.At the plan reviewer’s discretion, the plan reviewer has the authority to verify and question the stated exposure category on the plans if their personal knowledge of the site is in conflict with the designer’s.