Climatic and Geographic Design Criteria

2018 CODE - [February 1, 2021 - July 1, 2023]

IRC TABLE R301.2 (1) 
Climatic and Geographic Design Criteria - Click HERE for PDF.

IRC TABLE R301.2 (1)  Climatic and Geographic Design Criteria
Roof
Snow Loada		 Wind Designb Seismic Design Categoryc Subject to Damage From: Outside Design Temp– Heat/Cool Ice Barrier Under-layment Required Flood Hazardse Air Freezing Index Mean Annual Temp
 
Speed
  
Topographic Effects		 Weatheringd Frost Line Depth Termite Decay
25 psf 110 mph See footnoteb D2 Moderate 12” Slight to Moderate 24oF/83oF No NA 113 53oF
 
  1. When using this roof snow load it will be left to the engineer’s judgment whether to consider drift or sliding snow. However, rain on snow surcharge of 5 psf must be considered for roof slopes less than 5 degrees.
  2. Wind exposure category and Topographic effects (Wind Speed-up Kzt factor) shall be determined on a site-specific basis by the Engineer of Record (components and cladding need not consider topographic effects unless otherwise determined by the engineer of record).
  3. From IRC Table 301.2(1).
  4. Weathering may require a higher strength concrete or grade of masonry than necessary to satisfy the structural requirements of this code. The grade of masonry units shall be determined from ASTM C 34, C 55, C 62, C 73, C 90, C 129, C 145, C 216 or C 652.
  5. The City of Mercer Island participates in the National Flood Insurance Program (NFIP); Regular Program (No Special Flood Hazard Area). Further NFIP participation information: CID 530083, Initial FHBM Identified 06/28/74, Initial FIRM Identified 05/16/95, Current Effective Map Date (NSFHA), Reg-Emer Date 06/30/97.
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