WSR 03-18-076



[ Filed August 29, 2003, 2:13 p.m. ]

Original Notice.

Preproposal statement of inquiry was filed as WSR 03-08-027.

Title of Rule: Chapter 51-13 WAC, Washington State Ventilation and Indoor Air Quality Code.

Purpose: To consider amendments to the Washington State Ventilation and Indoor Air Quality Code.

Statutory Authority for Adoption: RCW 19.27.190 and 19.27.020.

Statute Being Implemented: Chapters 19.27 and 34.05 RCW.

Summary: The proposed rule amends two sections of the Washington State Ventilation and Indoor Air Quality Code to improve the radon collection system required by the code and reduce or eliminate future potential costs of radon mitigation.

Reasons Supporting Proposal: RCW 19.27.190 and 19.27.020.

Name of Agency Personnel Responsible for Drafting and Implementation: Al Rhoades, Olympia, Washington 98504-8350, (360) 725-2970; and Enforcement: Local jurisdictions.

Name of Proponent: Washington State Building Code Council, governmental.

Agency Comments or Recommendations, if any, as to Statutory Language, Implementation, Enforcement, and Fiscal Matters: The council is seeking comments on the issues proposed in the rules shown below.

Rule is not necessitated by federal law, federal or state court decision.

Explanation of Rule, its Purpose, and Anticipated Effects: The proposed rule amends chapter 51-13 WAC, Washington State Ventilation and Indoor Air Quality Code. One proposed change improves the code by providing more specific criteria for the sealed pipe required to be placed within the aggregate under concrete slabs for radon venting. The second proposed change provides for an improved method of venting under slab areas separated by footings or other barriers. These amendments are intended to reduce or eliminate future potential costs of radon mitigation by providing an improved venting system under concrete slabs at the time of initial construction.

Proposal Changes the Following Existing Rules: Section 503.2.6: Radon vent pipe size is required to be larger as the area under a concrete slab increases. Either PVC schedule 40 or equivalent ABS plastic pipe is specified as permitted for use. Inspection and labeling details are more specific.

Section 503.2.8: The exception which provides for connecting separate aggregate areas underneath a concrete slab is amended to require improved coverage of the areas being vented.

No small business economic impact statement has been prepared under chapter 19.85 RCW. No economic impact on small business was identified.

RCW 34.05.328 does not apply to this rule adoption. The State Building Code Council is not listed in this section as one of the agencies required to comply with this regulation.

Hearing Location: Spokane City Council Chambers, West 808 Spokane Falls Boulevard, Spokane, WA, on October 10, 2003, at 10:00 a.m.; and at the Holiday Inn Select/Renton, One Grady Way South, Renton, WA, on October 17, 2003, at 10:00 a.m.

Assistance for Persons with Disabilities: Contact

Sue Mathers by September 26, 2003, TDD (360) 753-7427 or (360) 725-2967.

Submit Written Comments to: Stan Price, Chairman, State Building Code Council, P.O. Box 48350, Olympia, WA 98504-8350, fax (360) 586-9383, e-mail, by October 17, 2003.

Date of Intended Adoption: November 21, 2003.

August 7, 2003

Tim Nogler

for Stan Price



AMENDATORY SECTION(Amending WSR 01-02-099, filed 1/3/01, effective 7/1/01)

WAC 51-13-503   Radon prescriptive requirements.  

503.1 Scope: This section applies to those counties specified in section 501.2.2. This section establishes prescriptive construction requirements for reducing the potential for radon entry into all Group R Occupancies, and for preparing the building for future mitigation if desired.

In all crawlspaces, except crawlspace plenums used for providing supply air for an HVAC system, a continuous air barrier shall be installed between the crawlspace area and the occupied area to limit air transport between the areas. If a wood sheet subfloor or other material is utilized as an air barrier, in addition to the requirements of section 502.1.6.2 of the Washington state energy code, all joints between sheets shall be sealed.

503.2 Floors in Contact with the Earth

503.2.1 General: Concrete slabs that are in direct contact with the building envelope shall comply with the requirements of this section.

EXCEPTION: Concrete slabs located under garages or other than Group R Occupancies need not comply with this chapter.

503.2.2 Aggregate: A layer of aggregate of four inch minimum thickness shall be placed beneath concrete slabs. The aggregate shall be continuous to the extent practical.

503.2.3 Gradation: Aggregate shall:

a) Comply with ASTM Standard C-33 Standard Specification for Concrete Aggregate and shall be size No. 8 or larger size aggregate as listed in Table 2, Grading Requirements for Coarse Aggregate; or

b) Meet the 1988 Washington State Department of Transportation specification 9-03.1 (3) "Coarse Aggregate for Portland Cement Concrete," or any equivalent successor standards. Aggregate size shall be of Grade 8 or larger as listed in section 9-03.1 (3) C, "Grading"; or

c) Be screened, washed pea gravel free of deleterious substances in a manner consistent with ASTM Standard C-33 with one hundred percent (100%) passing a one-half (1/2) inch sieve and less than five percent (5%) passing a No. 16 sieve. Sieve characteristics shall conform to those acceptable under ASTM Standard C-33.

EXCEPTION: Aggregate shall not be required if a substitute material or system, with sufficient load bearing characteristics, and having approved capability to provide equal or superior air flow, is installed.

503.2.4 Soil-Gas Retarder Membrane: A soil-gas retarder membrane, consisting of at least one layer of virgin polyethylene with a thickness of at least six mil, or equivalent flexible sheet material, shall be either placed directly under all concrete slabs so that the slab is in direct contact with the membrane, or on top of the aggregate with two inches (2") minimum of fine sand or pea gravel installed between the concrete slab and membrane. The flexible sheet shall extend to the foundation wall or to the outside edge of the monolithic slab. Seams shall overlap at least twelve inches. The membrane shall also be fitted tightly to all pipes, wires, and other penetrations of the membrane and sealed with an approved sealant or tape. All punctures or tears shall be repaired with the same or approved material and similarly lapped and sealed.

503.2.5 Sealing of Penetrations and Joints: All penetrations and joints in concrete slabs or other floor systems and walls below grade shall be sealed by an approved sealant to create an air barrier to limit the movement of soil-gas into the indoor air.

Sealants shall be approved by the manufacturer for the intended purpose. Sealant joints shall conform to manufacturer's specifications. The sealant shall be placed and tooled in accordance with manufacturer's specifications. There shall be no gaps or voids after the sealant has cured.

503.2.6 Radon Vent: One continuous sealed pipe shall run from a point within the aggregate under each concrete slab to a point outside the building. Joints and connections shall be permanently gas tight. The continuous sealed pipe shall interface with the aggregate in the following manner, or by other approved equal method: The pipe shall be permanently connected to a "T" within the aggregate area so that the two end openings of the "T" lie within the aggregate area. A minimum of five feet of flexible or rigid perforated drain pipe ((of three inches minimum diameter)) shall join to and extend from the "T." The pipe shall be sized as follows:

a. 3" minimum diameter for slabs 750 sq. ft. or smaller,

b. 4" minimum diameter for slabs larger than 750 sq. ft. and smaller than 3000 sq. ft., or

c. Radon venting systems for slabs 3000 sq. ft. or larger shall be approved.

Acceptable sealed plastic pipe shall be smooth walled, and shall be permitted to include either PVC schedule 40 or ABS schedule of equivalent wall thickness.

The perforated pipe shall remain in the aggregate area and shall not be capped at the ends. The "T" and it's perforated pipe extensions shall be located at least ((five)) ten feet horizontally from the exterior perimeter of the aggregate area. Below grade ducting shall remain exposed in the aggregate area for inspection.

The continuous sealed pipe shall terminate no less than twelve inches above the eave, and more than ten horizontal feet from a woodstove or fireplace chimney, or operable window. The continuous sealed pipe shall be permanently labeled "radon ((vent." The)) vent" on each floor and attic space. At least one label shall be placed so as to remain visible to an occupant.

((The minimum pipe diameter shall be three inches unless otherwise approved. Acceptable sealed plastic pipe shall be smooth walled, and may include either PVC schedule 40 or ABS schedule of equivalent wall thickness.))

The entire sealed pipe system shall be sloped to drain to the sub-slab aggregate.

The sealed pipe system may pass through an unconditioned attic before exiting the building; but to the extent practicable, the sealed pipe shall be located inside the thermal envelope of the building in order to enhance passive stack venting.

EXCEPTION: A fan forced sub-slab depressurization system includes:

1) Soil-gas retarder membrane as specified in section 503.2.4;
2) Sealing of penetrations and joints as specified in section 503.2.5;
3) ((A three-inch)) Continuous sealed radon pipe shall run from a point within the aggregate under each concrete slab to a point outside the building;
4) Joints and connections ((may)) shall be gas tight, and may be of either PVC schedule 40 or ABS schedule of equivalent in wall thickness;
5) A label of "radon vent" on each floor and attic space shall be placed on the pipe so ((as to remain)) at least one label remains visible to the occupant;
6) Fan circuit and wiring as specified in section 503.2.7 and a fan.
((If the sub-slab depressurization system is exhausted through the concrete foundation wall or rim joist, the exhaust terminus shall be a minimum of six feet from operable windows or outdoor air intake vents and shall be directed away from operable windows and outdoor air intake vents to prevent radon re-entrainment.))

503.2.7 Fan Circuit and Wiring and Location: An area for location of an in-line fan shall be provided. The location shall be as close as practicable to the radon vent pipe's point of exit from the building, or shall be outside the building shell; and shall be located so that the fan and all downstream piping is isolated from the indoor air.

Provisions shall be made to allow future activation of an in-line fan on the radon vent pipe without the need to place new wiring. A one hundred ten volt power supply shall be provided at a junction box near the fan location.

503.2.8 Separate Aggregate Areas: If the four-inch aggregate area underneath the concrete slab is not continuous, but is separated into distinct isolated aggregate areas by a footing or other barrier, a minimum of one radon vent pipe shall be installed into each separate aggregate area.

EXCEPTION: Separate aggregate areas may be considered a single area ((if a minimum three-inch diameter connection joining the separate areas is provided for every thirty feet of barrier separating those areas)) and a separate vent pipe is not required if flexible or rigid perforated drain pipe connects the separate aggregate areas below grade directly to the sealed vent pipe.

503.2.9 Concrete Block Walls: Concrete block walls connected to below grade areas shall be considered unsealed surfaces. All openings in concrete block walls that will not remain accessible upon completion of the building shall be sealed at both vertical and horizontal surfaces, in order to create a continuous air barrier to limit the transport of soil-gas into the indoor air.

[Statutory Authority: RCW 19.27.190, 19.27.020. 01-02-099, 51-13-503, filed 1/3/01, effective 7/1/01. Statutory Authority: RCW 19.27.190(2) and 1992 c 132. 93-02-056, 51-13-503, filed 1/6/93, effective 7/1/93. Statutory Authority: RCW 19.27.190. 91-01-102, 51-13-503, filed 12/18/90, effective 7/1/91.]

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