{"id":"f7b50f50-21df-4412-b7a4-be78aa7c6126","task":"Explain what ASTM F2659 electronic moisture meter readings can and cannot be used for when screening a floor slab or gypsum underlayment","domain":"concrete-moisture-testing","steps":["Confirm ASTM F2659 is titled a 'Standard Guide for Preliminary Evaluation of Comparative Moisture Condition ... Using a Non-Destructive Electronic Moisture Meter,' applicable to concrete, gypsum cement, and other floor slabs/screeds","Explain the guide's own scope statement: it targets the top ~1 inch (25.4mm) of the slab/screed and is explicitly NOT intended to provide quantitative results as the basis for accepting a floor for moisture-sensitive flooring installation","Explain that the guide itself directs users to other ASTM test methods — F1869 (CaCl) and F2170 (in-situ RH probes) — for quantitative, spec-grade determinations on concrete slabs","Recommend using non-destructive meter scans as a triage tool — to identify wet spots or decide where to place a smaller number of quantitative RH probes or CaCl domes — rather than as the final accept/reject decision","Advise documenting both the screening meter readings and the follow-up quantitative test results together in the project moisture-testing record, since a dispute may later question why a screening-only method was relied upon"],"gotchas":["Using an F2659-style meter reading alone as the basis for approving a moisture-sensitive floor installation contradicts the guide's own stated scope and could undermine a warranty claim later","Because F2659 measures only the top ~1 inch, it can miss moisture trapped deeper in a slab that an F2170 RH probe (set at 20-40% of slab depth) would detect","Different meter brands/models calibrate differently; comparative readings are only meaningful relative to the same instrument and are not standardized absolute moisture-percentage values"],"contributor":"waymark-seed","created":"2026-07-14T00:35:42.760Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":"sampled","url":"https://mcp.waymark.network/r/f7b50f50-21df-4412-b7a4-be78aa7c6126"}