4-5-055 INTERNATIONAL RESIDENTIAL CODE ADOPTED:

The 2021 Edition of the International Residential Code (IRC), as adopted and amended by the State Building Code Council in chapter 51-51 WAC, as published by the International Code Council, is adopted by reference, with the City’s amendments thereto, as specified in subsections A and B of this Section. Chapter 1, Scope and Administration, is not adopted and the Construction Administrative Code, as set forth in RMC 4-5-060, shall be used in place of IRC Chapter 1, Scope and Administration; provided, that Chapters 11 and 25 through 43 of the IRC are not adopted. The energy code is regulated by chapter 51-11R WAC; the plumbing code is regulated by chapter 51-56 WAC; the electrical code is regulated as adopted by RMC 4-5-040. The standards for liquefied petroleum gas installations shall be 2020 NFPA 58 (Liquefied Petroleum Gas Code) and 2021 NFPA 54 (National Fuel Gas Code). All other fuel gas installations shall be regulated by the 2021 International Mechanical Code and 2021 International Fuel Gas Code. Appendix Q – Tiny Houses (WAC 51-51-60104), Appendix T, Solar-Ready Provisions – Detached One- and Two-Family Dwellings, Multiple Single-Family Dwellings – Townhouses (WAC 51-51-60106), and Appendix U – Dwelling Unit Fire Sprinkler Systems (WAC 51-51-60105), are adopted.

A. CITY AMENDMENTS TO IRC TABLE R301.2(1), CLIMATIC AND GEOGRAPHIC DESIGN CRITERIA:

Table R301.2(1) of the International Residential Code is amended to read as follows:

IRC Table R301.2(1)

Climatic and Geographic Design Criteria

Ground Snow Load (nsf)1	Wind Design				Seismic Design Category	Subject to Damage From:			Ice Barrier Underlayment Required	Flood Hazards5	Air Freezing Index	Mean Annual Temp.
	Speed (mph)2	Topographic Effects3	Special Wind Region	Windborne Debris Zone		Weathering4	Frost Line Depth	Termite
20	100		No	No	D2	Moderate	12"	Slight	No	N/A	113	50ºF

 

Manual J Design Criteria

Elevation	Altitude Correction Factor	Coincident Wet Bulb	Indoor Winter Design Dry-Bulb Temperature	Indoor Winter Design Dry-Bulb Temperature	Outdoor Winter Design Dry-Bulb Temperature	Heating Temperature Difference
338 ft	0.99	66ºF	72ºF	72ºF	24ºF	48ºF

 

Latitude	Daily Range	Indoor Summer Design Relative Humidity	Summer Design Gains	Indoor Summer Design Dry-Bulb Temperature	Outdoor Summer Design Dry-Bulb Temperature	Cooling Temperature Difference
47° 34' 39"	M	50%	5	75ºF	83ºF	8ºF

Footnotes:

1. This is the minimum roof snow load. When using this snow load it will be left to the engineer’s judgment whether to consider drift or sliding snow. However, rain on snow surcharge of five pounds per square foot (5 psf) must be considered for roof slopes less than five degrees (5º).

2. The basic wind speed is determined from the basic wind speed map in Figure R301.2(2) of the International Residential Code. Wind exposure category shall be determined on a site-specific basis in accordance with Section R301.2.1.4 of the International Residential Code.

3. Topographic effects (Wind Speed-up Kzt factor) shall be determined on a site-specific basis in accordance with Section R301.2.1.5 of the International Residential Code.

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 C34, C55, C62, C73, C90, C129, C145, C216 or C652.

5. The City of Renton participates in the National Flood Insurance Program (NFIP) as specified in City of Renton Resolution No. 1984, dated April 21, 1975. On August 10, 2020, the City adopted by Ordinance No. 5977, “The Flood Insurance Study (FIS) for King County, Washington and Incorporated Areas,” effective for all communities in King County on August 19, 2020, with the accompanying Flood Insurance Rate Maps (FIRMs). The FIS and FIRMs are on file at the City of Renton, 1055 South Grady Way, Renton, WA 98057.

B. EXCEPTIONS:

The provisions of this code do not apply to temporary growing structures used solely for the commercial production of horticultural plants including ornamental plants, flowers, vegetables, and fruits. “Temporary growing structure” means a structure that has the sides and roof covered with polyethylene, polyvinyl, or similar flexible synthetic material and is used to provide plants with either frost protection or increased heat retention. A temporary growing structure is not considered a building for purposes of this code.

The provisions of this code do not apply to the construction, alteration, or repair of temporary worker housing except as provided by rule adopted under chapter 70.114A RCW or Chapter 37, Laws of 1998 (SB 6168). “Temporary worker housing” means a place, area, or piece of land where sleeping places or housing sites are provided by an employer for his or her employees or by another person, including a temporary worker housing operator, who is providing such accommodations for employees, for temporary, seasonal occupancy. (Ord. 5085, 6-21-2004; Amd. Ord. 5157, 9-26-2005; Ord. 5450, 3-2-2009; Ord. 5676, 12-3-2012; Ord. 5710, 4-14-2014; Ord. 5810, 7-11-2016; Ord. 6010, 1-25-2021; Ord. 6133, 3-4-2024)