International Subfloor Acceptance Protocol (NWFA / DIN)
Based on NWFA (North America),
DIN / EN (Europe), and
ASTM international standards.
Concrete Subfloor Requirements
Flatness: ≤ 2 mm per 2 m (DIN 18202) or ≤ 1/8″ per
6′ (NWFA).
Moisture: ≤ 2% CM for cement screed, ≤ 0.5% CM for
anhydrite (EN / DIN). ASTM F2170 ≤ 75% RH.
Strength: Minimum 3000 psi (NWFA) / C20/25 (EN).
Vapor barrier: Recommended 6‑mil polyethylene
(≈0.15 mm, perm ≤ 0.13).
Cleanliness: No sealers, waxes, oils, paint, dust
(NWFA / DIN 18356).
No cracks or hollow spots.
Job Site Conditions
Wood flooring moisture: 7–11% (EN 13226) / 6–9%
(NWFA).
Ambient humidity: 40–60% RH (maintained for 7–14
days prior).
Room temperature: 18–22°C (64–72°F) — NWFA minimum
60°F also acceptable.
⚠️ Disclaimer: JOVI is an independent technical tool
and is not affiliated with NWFA, DIN, CEN, or ASTM. This document is a
professional summary of international requirements, including moisture
testing (ASTM F2170) and surface flatness (DIN 18202). All calculations
are provided for estimation purposes only.