Exterior wall envelope: water-resistive barrier + drainage path to weep water out

Description

Exterior walls must be constructed to PREVENT accumulation of water within the wall assembly. That requires (a) a water-resistive barrier (WRB) behind the exterior cladding (R703.2) AND (b) a drainage path for any water that penetrates the cladding. Concrete + masonry walls per Chapter 6 are exempted from the WRB rule; alternative wall envelopes passing ASTM E331 (4×8 ft assembly, 6.24 psf differential, 2-hour exposure) are also allowed.

Why this exists

Drainage-plane construction is the modern standard. Just a WRB without a drainage path can trap water and cause mold/rot. Rain-screen detailing (battens or proprietary mat behind cladding) is the most reliable drainage solution. Architects specifying fiber-cement or vinyl over a hous wrap without a drainage plane in wet climates risk early envelope failure.

Categories

Applies to

• Jurisdiction: New York State

Source

Solver enforcement

Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.

Related directives

• Habitable space minimum ceiling height · IRC R305.1
• Wind design · IRC R301.2.1
• Seismic provisions · IRC R301.2.2
• Snow loads · IRC R301.2.3
• Floodplain construction · IRC R301.2.4