Why it matters in Reno specifically
Reno's air is dry — afternoon relative humidity averages around 30% over the year and runs in the high teens and low twenties in summer. That leads a lot of homeowners, and some installers, to assume moisture is not a local problem. It is, for two reasons.
First, slab moisture comes from the ground, not the air. A concrete slab in contact with soil wicks moisture upward continuously; without an intact vapor retarder under the slab (common in older Reno and Sparks homes), that moisture emerges at the surface, and anything glued or laid on top of it takes the hit. The air in the room above has nothing to do with it.
Second, dry air on top plus moisture underneath is the worst combination for wood. A board that is drying from its top face while absorbing moisture through its bottom face cups — edges up, center down. A humid climate wets both faces roughly evenly; Reno's does not. That asymmetry is why moisture testing is arguably more important here than in a wet climate, not less. The climate and flooring page covers the wood-movement side in depth.
The tests, and what each one tells you
| Test | Subfloor | What it measures | How it works |
|---|---|---|---|
| ASTM F2170 (in-situ RH) | Concrete | Relative humidity inside the slab, at depth | Holes are drilled to a depth proportional to slab thickness, probes are sealed in and left to equilibrate, then read. Reflects the moisture the floor will actually see once sealed over. The industry's preferred method for critical installs. |
| ASTM F1869 (calcium chloride) | Concrete | Moisture vapor emission rate at the surface, in lbs per 1,000 sq ft per 24 hours | A sealed dish of desiccant sits on the slab for a set period and is weighed before and after. Simpler and older; sensitive to room conditions and only reads the top of the slab. |
| Moisture meter (pin or pinless) | Wood (plywood/OSB) and the new flooring | Moisture content of the wood, as a percentage | Readings taken across the subfloor and on the new flooring after acclimation. NWFA guideline: the two should be within 4 points for strip flooring, 2 points for plank. |
Pass/fail limits for the slab tests are set by the flooring manufacturer for the specific product and adhesive, not by a single universal number — which is why a good quote names the product and the test together. Ask for both.
What should be on the quote
- Which subfloor you have — slab or wood — stated, because it changes the test.
- Which test will be run, by name, and whether it is included or a separate line.
- The product's moisture limit, or at least a statement that the result will be checked against the manufacturer's specification.
- What happens on a fail — a mitigation option and its price, or a material change — so a failed test is not a surprise change order.
- Acclimation — for wood floors, how long the material will sit in the room at normal living conditions before installation. NWFA's guidance is that the home should be held at normal occupied conditions (roughly 60–80°F and 30–50% relative humidity) for at least five days before materials arrive, then the flooring acclimates to it.
A quote for hardwood, laminate, or glue-down flooring over a slab that mentions none of this is not necessarily from a bad installer, but it is an incomplete quote, and the cheapest bid is often cheapest precisely because this step is missing.
How much each floor cares
| Floor | Sensitivity to subfloor moisture | Typical requirement |
|---|---|---|
| Solid hardwood | Very high | Wood subfloor only; meter check; never directly on slab or below grade |
| Engineered hardwood (glue-down) | High | Slab test to the adhesive/product limit; often a vapor retarder |
| Laminate | High (fiberboard core swells) | Vapor barrier over concrete as a warranty condition; flatness check |
| Glue-down LVP | Moderate to high (adhesive can fail) | Slab test to the adhesive's limit |
| Floating LVP | Low to moderate | Flatness matters more; some products still specify a vapor barrier |
| Carpet | Low (but pad can mildew) | Address obvious dampness; moisture-barrier pad in risk areas |
| Tile | Low for the tile; substrate flatness and rigidity matter most | Waterproofing membrane where water is expected |
If the test fails
A failing slab result is information, not a dead end, and it is far cheaper to have at the quote stage than after the floor is down. The usual paths, from least to most expensive: choose a floor that tolerates the reading (floating LVP, tile); apply a moisture-mitigation system or vapor retarder rated for the measured level, which adds a real line to the quote; or fix the source — grading, gutters, a plumbing leak under the slab. What a reputable installer will not do is proceed with hardwood or laminate over a failed slab and hope.
The license angle
Moisture testing is part of competent practice, not a separate licensed trade — any flooring installer working under Nevada's NSCB Classification C-16a ("Covering Floors") should be doing it for wood, laminate, and glue-down floors, and a C-20 ("Tiling") contractor should be checking substrate condition before tile. Verify the classification at https://app.nvcontractorsboard.com; the license guide explains the C-16a/C-20 split and the vetting guide covers the rest of the pre-signing checklist.
Sources
ASTM F2170 (Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes) and ASTM F1869 (Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride); National Wood Flooring Association installation guidelines as summarized in Hardwood Floors Magazine, "A Wood Floor Installer's Guide to Moisture Testing" (August 2024); Reno humidity averages from published climate normals (secondary source), September 2026. Product-specific limits come from each manufacturer's installation instructions.