AquabarB Moisture Vapor Retarder Underlayment

AquabarB is a nonreinforced, GradeB, asphaltlaminated kraft paper underlayment (30/30/30 construction) that serves as an effective ClassII moisture vapor retarder for interior hardwood and tile installations backed by over 75 years of trusted performance from Fortifiber:contentReference[oaicite:1]{index=1}.

With a water vapor permeance below 1perm, it slows moisture migration to help prevent wood floor damage (buckling, cupping, splitting). As a semipermeable material, it also minimizes condensation risk compared to plastic sheets and acts as a clean slipsheet that reduces squeaks, dust, and noise:contentReference[oaicite:2]{index=2}.

• Meets ASTME96 (<1perm), ASTMD779 (>16hrs water resistance), ASTMD828 (20lb/in tensile strength):contentReference[oaicite:3]{index=3}
• Complies with Federal UUB790a Type1 GradeB Style1a and ASTM F1861 TypeTP:contentReference[oaicite:4]{index=4}
• Meets IBC/IRC ClassII vapor retarder and ANSI A108 standards for hardwood/tile installations:contentReference[oaicite:5]{index=5}
• Available in 36″ 167′ (500sqft) and 36″ 334′ (1,000sqft) rolls; weighs ~3lb per 100sqft:contentReference[oaicite:6]{index=6}
• Certified low-emitting under Californias CA01350 Indoor Air Quality standard:contentReference[oaicite:7]{index=7}

Ideal uses: Serves as a moisture vapor retarder under naildown wood floors and as a cleavage membrane under tile/backerboard. Not waterproof do not use in wet areas (showers, exterior):contentReference[oaicite:8]{index=8}.

Installation tip: Lay over a clean, dry, structurally sound subfloor with 4 overlap at seams. May be loose-laid or stapled easier and cleaner than felt or plastic film:contentReference[oaicite:9]{index=9}.

Choose AquabarB for a reliable, easy-to-install moisture retarder that helps protect hardwood and tile flooring. Available now at .