Two Concrete Moisture Numbers May Not Be Comparable
A facilities spreadsheet can contain several moisture numbers without containing a valid trend. Before comparing results, establish what each method measured and why it was selected. Similar units, dates or device screens do not automatically make two readings suitable for the same installation decision.
Preserve each method’s identity
Keep the original report or field record with the location, method, date and stated conditions. Do not shorten every result to moisture percentage. NRMCA’s slab-moisture guidance distinguishes the installation requirements of different floor systems. A result should be interpreted against the applicable method and selected system, rather than whichever limit is easiest to find in another report.
Ask the reviewer to classify the relationship
Are the records repeat measurements under a comparable procedure, complementary observations, or results that should not be combined? Ask for that distinction before building a graph or calculating an average. An apparent increase can reflect a different method or location. This does not establish that the building is unchanged either; it identifies a comparison that needs a qualified interpretation.
Make the procurement consequence explicit
If a floor-covering decision depends on the result, identify who reviews the evidence and which requirement governs the proposed assembly. Keep screening observations separate from acceptance testing. Ask whether further work is needed to answer the actual decision, including any limits on accessible locations. A clearer spreadsheet retains uncertainty without converting an inconsistent collection of numbers into a site-wide pass or fail.
Copyable worksheet
Use one row for each field. Mark unknown information clearly and retain the original records.
| Field | Your note |
|---|---|
| Original report and method | ____________________ |
| Location and conditions | ____________________ |
| Selected installation requirement | ____________________ |
| Comparable, complementary or separate | ____________________ |
| Decision owner and next evidence | ____________________ |
Worked example
Illustrative example: a fictional facilities team receives a handheld screening value and a different installation test result. The team stores both but does not chart them as one rising trend. The flooring decision is referred to the appropriate reviewer using the actual system requirements.