🛡️ Aquabar “B” Moisture Vapor Retarder Underlayment

Aquabar “B” is a non‑reinforced, Grade B, asphalt‑laminated kraft paper underlayment (30/30/30 construction) that serves as an effective Class II 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 1 perm, it slows moisture migration to help prevent wood floor damage (buckling, cupping, splitting). As a semi‑permeable 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 ASTM E96 (<1 perm), ASTM D779 (>16 hrs water resistance), ASTM D828 (20 lb/in tensile strength) :contentReference[oaicite:3]{index=3}
• ✔️ Complies with Federal UU‑B‑790a Type 1 Grade B Style 1a and ASTM F1861 Type TP :contentReference[oaicite:4]{index=4}
• ✔️ Meets IBC/IRC Class II vapor retarder and ANSI A108 standards for hardwood/tile installations :contentReference[oaicite:5]{index=5}
• ✔️ Available in 36" × 167' (500 sq ft) and 36" × 334' (1,000 sq ft) rolls; weighs ~3 lb per 100 sq ft :contentReference[oaicite:6]{index=6}
• ✔️ Certified low-emitting under California’s CA‑01350 Indoor Air Quality standard :contentReference[oaicite:7]{index=7}

Ideal uses: Serves as a moisture vapor retarder under nail‑down 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 Aquabar “B” for a reliable, easy-to-install moisture retarder that helps protect hardwood and tile flooring. Available now at PreFloorTools.com.