WAC 51-11-1313   Moisture control.  


1313.1 Vapor Retarders: Vapor retarders shall be installed on the warm side (in winter) of insulation as required by this section.

EXCEPTION:

Vapor retarder installed with not more than 1/3 of the nominal R-value between it and the conditioned space.

1313.2 Roof/Ceiling Assemblies: Roof/ceiling assemblies where the ventilation space above the insulation is less than an average of twelve inches shall be provided with a vapor retarder. (For enclosed attics and enclosed rafter spaces see Section 1203.2 of the International Building Code.) Roof/ceiling assemblies without a vented airspace, allowed only where neither the roof deck nor the roof structure are made of wood, shall provide a continuous vapor retarder with taped seams.

EXCEPTION:

Vapor retarders need not be provided where all of the insulation is installed between the roof membrane and the structural roof deck.

1313.3 Walls: Walls separating conditioned space from unconditioned space shall be provided with a vapor retarder.


1313.4 Floors: Floors separating conditioned space from unconditioned space shall be provided with a vapor retarder.


1313.5 Crawl Spaces: A ground cover of six mil (0.006 inch thick) black polyethylene or approved equal shall be laid over the ground within crawl spaces. The ground cover shall be overlapped twelve inches minimum at the joints and shall extend to the foundation wall.

EXCEPTION:

The ground cover may be omitted in crawl spaces if the crawl space has a concrete slab floor with a minimum thickness of three and one-half inches.

[Statutory Authority: RCW 19.27A.020, 19.27A.045. 04-01-106, § 51-11-1313, filed 12/17/03, effective 7/1/04. Statutory Authority: RCW 19.27A.025, 19.27A.045. 01-03-010, § 51-11-1313, filed 1/5/01, effective 7/1/01. Statutory Authority: RCW 19.27A.025. 93-21-052, § 51-11-1313, filed 10/18/93, effective 4/1/94.]