Washington Administrative Code › Title 51 - Enterprise Services, Department of (Building Code Council) › Chapter 51-51 - State Building Code adoption and amendment of the 2021 edition of the International Residential Code › Section 51-51-0703 - Section R703-Exterior covering

Current through Register Vol. 24-14, July 15, 2024
R703.1.1 Water resistance.
The exterior wall
				envelope shall be designed and constructed in a manner that prevents the
				accumulation of water within the wall assembly by providing a water-resistant
				barrier behind the exterior veneer as required by Section R703.2 and a means of
				draining water that enters the assembly to the exterior. Protection against
				condensation in the exterior wall assembly shall be provided in accordance with
				Section R702.7 of this code.
EXCEPTIONS:
1. A weather-resistant exterior wall envelope shall not
						  be required over concrete or masonry walls designed in accordance with Chapter
						  6 and flashed according to Section R703.4 or R703.8.
2. Compliance with the requirements for a means of
						  drainage, and the requirements of Sections R703.2 and R703.4, shall not be
						  required for an exterior wall envelope that has been demonstrated to resist
						  wind-driven rain through testing of the exterior wall envelope, including
						  joints, penetrations and intersections with dissimilar materials, in accordance
						  with ASTM E 331 under the following conditions:
2.1. Exterior wall envelope test assemblies shall
						  include at least one opening, one control joint, one wall/eave interface and
						  one wall sill. All tested openings and penetrations shall be representative of
						  the intended end-use configuration.
2.2. Exterior wall envelope test assemblies shall be at
						  least 4 feet (1219 mm) by 8 feet (2438 mm) in size.
2.3. Exterior wall assemblies shall be tested at a
						  minimum differential pressure of 6.24 pounds per square foot (299Pa).
2.4. Exterior wall envelope assemblies shall be
						  subjected to a minimum test exposure duration of 2 hours.
3. The requirement for a means of drainage shall not be
						  construed to mean an air space cavity under the exterior cladding for an
						  exterior wall clad with panel or lapped siding made of plywood, engineered
						  wood, hardboard, or fiber cement. A water-resistive barrier as required by
						  Section R703.2 will be required on exterior walls.
The exterior wall envelope design shall be considered to resist
				wind-driven rain where the results of testing indicate that water did not
				penetrate control joints in the exterior wall envelope; joints at the perimeter
				of opening penetration; or intersections of terminations with dissimilar
				materials.
R703.10.2 Lap siding.
Fiber-cement lap siding
				having a maximum width of 12 inches (305 mm) shall comply with the requirements
				of ASTM C 1186, Type A, minimum Grade II or ISO 8336, Category A, minimum Class
				2. Lap siding shall be lapped a minimum of 1 1/4 inches (32 mm) and lap siding
				shall be installed in accordance with the manufacturer's installation
				instructions or shall be designed to comply with Section R703.1. Lap siding
				courses shall be installed with the fastener heads exposed or concealed, in
				accordance with Table R703.3(1) or approved manufacturer's
				instructions.
Statutory Authority:
				  RCW
				    19.27.031 and
				  chapters
				  19.27 and
				  34.05 RCW. 13-04-068, §
				  51-51-0703, filed 2/1/13, effective 7/1/13. Statutory Authority:
				  RCW
				    19.27.031 and
				  19.27.074. 10-03-098, §
				  51-51-0703, filed 1/20/10, effective 7/1/10. Statutory Authority:
				  RCW
				    19.27.190,
				  19.27.020, and
				  chapters
				  19.27 and
				  34.05 RCW. 08-01-102, §
				  51-51-0703, filed 12/18/07, effective
				  4/1/08.