NWFA CWFI flashcards
NWFA CWFI · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Equilibrium moisture content
- The moisture level wood reaches when its vapor pressure matches the surrounding air at a given temperature and relative humidity. Typical conditioned interiors hold wood near 6 to 9 percent.
- Cupping
- A condition where board edges sit higher than the center, indicating higher moisture at the bottom face. Commonly caused by a wet subfloor, plumbing leak, or humid crawl space beneath the floor.
- Crowning
- A condition where the board center sits higher than the edges, indicating higher moisture at the top face. Often results from sanding a cupped floor before it dried, or from surface moisture.
- Seasonal gapping
- Normal shrinkage gaps between boards during heating season when interior relative humidity drops. Gaps that close in humid months are generally environmental, not a manufacturing defect.
- Acclimation
- Conditioning flooring in the installation environment until its moisture content stabilizes near the expected in-service level. Skipping it commonly causes gapping, cupping, or fastener problems after installation.
- Moisture meter correction
- Pin and pinless meters read differently by species, temperature, and meter type. Readings must be adjusted per the meter's species correction table before conclusions about moisture content are drawn.
- Normal lighting inspection
- Finished floors are judged under ordinary lighting from a standing position. Raking light or close-up viewing exaggerates natural grain and color variation beyond accepted standards.
- Natural wood variation
- Differences in grain, color, and texture between boards are inherent characteristics of wood. They are not defects and are generally excluded from finish or appearance complaints.
- Site-related finish failure
- Finish problems caused by jobsite conditions such as inadequate acclimation, high subfloor moisture, or HVAC not running. These differ from product defects and shift responsibility to the installer or builder.
- Mill glaze
- A polished, compressed surface on some sanded boards that resists finish penetration. It is addressed by proper sanding sequence and screening rather than by extra finish coats.
- Inspection documentation
- A report should record meter type and calibration, number and location of readings, environmental conditions, and moisture content of flooring, subfloor, and framing at the time of inspection.
- Moisture content differential
- The gap between flooring and subfloor moisture content. A difference of roughly 2 to 4 percentage points or more warrants investigation before blaming the product.
- Wood movement direction
- Wood moves predominantly across its width as moisture changes, while lengthwise movement is negligible. This drives the need for perimeter expansion space and controls gapping behavior.
- Relative humidity target
- Interior relative humidity is generally maintained between about 30 and 50 percent. Sustained levels below 30 percent during heating commonly produce shrinkage gaps.
- Calcium chloride test
- ASTM F1869 test measuring moisture vapor emission from concrete, expressed in pounds per 1,000 square feet per 24 hours. A common limit is 3 pounds.
- In-situ relative humidity test
- ASTM F2170 test measuring relative humidity inside a concrete slab using embedded probes. A commonly cited limit is 75 percent relative humidity unless the manufacturer states otherwise.
- Subfloor flatness tolerance
- Typically 3/16 inch in 10 feet, or 1/8 inch in 6 feet, for most wood flooring. High spots and low spots must be corrected before installation begins.
- Wood subfloor moisture limit
- Wood subfloor moisture content should generally not exceed about 12 percent and should fall within roughly 2 to 4 percentage points of the flooring moisture content.
- Perimeter expansion space
- A gap left at walls and fixed obstructions to allow widthwise movement. The required size depends on flooring width, span, and expected seasonal moisture change per the manufacturer.
- Glue-down installation
- Flooring is adhered to the substrate with an approved adhesive. The adhesive, trowel size, and open time are specified by the manufacturer and affect moisture and movement performance.
- Floating installation
- Boards are joined to each other rather than to the subfloor, often over an underlayment. Floating floors require larger perimeter expansion space and protection at doorways and transitions.
- Nail or staple installation
- Fasteners are driven through the tongue into a wood subfloor at manufacturer-specified intervals. Fastener type, length, and angle affect squeaks and board movement.
- Sanding grit progression
- Rough sanding with coarse grit followed by progressively finer grits removes old finish and levels the floor. Skipping grits can leave scratches that show after finish is applied.
- Screening between coats
- Light abrasion between finish coats improves adhesion and removes dust nibs. The screen grit and any tacking procedure are specified by the finish manufacturer.
- Finish spread rate
- The coverage rate specified by the finish manufacturer, usually in square feet per gallon. Applying too thin or too thick a coat causes adhesion and durability problems.
- Jobs-ite conditions
- Interior temperature and humidity must be controlled before, during, and after installation and finishing. Typical targets are about 60 to 80 degrees Fahrenheit and 30 to 50 percent relative humidity.
- Manufacturer instructions precedence
- Where NWFA guidelines and manufacturer instructions conflict, the more restrictive requirement generally governs. Following neither can void warranties and shift responsibility to the installer.
- Underlayment requirements
- The product and substrate dictate whether an underlayment is needed and which type. Using the wrong underlayment can trap moisture or cause movement and noise problems.
- Subfloor deflection criteria
- The floor structure must be stiff enough to limit deflection under load. Excessive deflection causes squeaks, fastener movement, and finish cracking regardless of installation quality.
- Moisture barrier purpose
- A barrier over a crawl space or on-grade concrete limits vapor movement into the flooring. Missing or damaged barriers are a common root cause of cupping complaints.
- Finish cure versus dry time
- Dry time is when the floor can be walked on; cure time is when the finish reaches full hardness. Confusing the two leads to premature traffic damage and inspection disputes.
- Applicable guideline citation
- Inspection findings should cite the specific NWFA guideline and the manufacturer's written instruction relied upon. Vague opinions without a cited standard carry little weight in disputes.