Wood and Laminate Flooring Inspector cheat sheet

Moisture: wood flooring equilibrates to its environment; acceptable in-service moisture content varies by region and species but commonly falls near 6-9% in heated interiors. Compare flooring, subfloor, and ambient readings before blaming material.

Wood moisture content (MC%) = (wet weight − oven-dry weight) / oven-dry weight × 100. A 100 g sample drying to 90 g is 11.1% MC.

Equilibrium moisture content (EMC) responds to relative humidity and temperature; a floor installed at one EMC and exposed to another will shrink or swell across grain, causing gaps or cupping.

Cupping = edges high, center low (convex top). Crown = center high, edges low. Cupping usually follows moisture gain from below; crowning often follows surface moisture or over-sanding after cupping.

Gaps between boards in heating season are commonly seasonal shrinkage; measure gap width, note RH history, and check whether gaps close in humid months before assigning cause.

Subfloor flatness tolerance for wood flooring is typically 3/16 in. in 10 ft (or 1/8 in. in 6 ft); check with a 10 ft straightedge before installation.

Concrete slab moisture testing: calcium chloride test (ASTM F1869) reports lb/1000 ft²/24 h; relative humidity probe (ASTM F2170) reports in-situ RH%. Both are valid; probes measure the slab, not just the surface.

Inspection sequence: document site conditions (temperature, RH, HVAC operation), measure MC of flooring and subfloor, verify flatness, then map defects with photos, measurements, and a moisture map.

Wood species and cut affect movement: plainsawn boards move more in width than quartersawn; wider boards and rift/quarter sawn material behave differently under humidity swings.

Laminate is a composite: wear layer, decorative print, core (usually HDF), and backing. Core swelling from water is the most common failure mode and is generally not reversible.

Laminate requires an expansion gap at perimeter walls and fixed objects, typically 1/4 to 3/8 in., hidden by baseboard or quarter round. Missing gaps cause buckling or peaking.

Laminate is a floating floor: it must not be fastened to the subfloor and requires an underlayment. Inspect for fasteners, glue-down errors, or missing underlayment.

Subfloor flatness for laminate is commonly 3/16 in. in 10 ft; check with a straightedge and correct with leveling compound before installation.

Acclimation: laminate should be acclimated in the room in unopened cartons for the manufacturer's stated period (often 48 hours) at normal living conditions; verify with installation records.

Peaking (tenting) at seams often results from inadequate expansion space, tight fits against walls, or moisture swelling of the core; check perimeter gaps and moisture exposure.

Laminate is not a moisture-tolerant floor: standing water, wet mopping, and plumbing leaks cause edge swelling, joint separation, and delamination of the wear layer.

Inspection evidence: measure joint gaps, check for core swelling at seams, verify underlayment type and vapor barrier, and document transition profiles and perimeter clearances.