IICRC Wood and Laminate Flooring Inspector (WLFI)

Which species is the industry benchmark on the Janka hardness scale, against which other domestic flooring species are typically compared?

• AHard maple
• BRed oak
• CHickory
• DBlack walnut

What is the approximate Janka hardness rating of hickory?

• A~1010
• B~1290
• C~1450
• D~1820

Which cut method produces the most dimensionally stable wood flooring with the straightest, most consistent grain?

• APlain-sawn
• BRift-sawn
• CQuarter-sawn
• DLive-sawn

A board cut so the growth rings intersect the face at 30 to 60 degrees is described as:

• APlain-sawn
• BRift-sawn
• CQuarter-sawn
• DEnd-grain

Compared to red oak, white oak is generally:

• ASofter and more open-grained
• BSlightly harder and more closed-grained, with better moisture resistance
• CIdentical in hardness but lighter in color
• DLess dimensionally stable due to wider rays

Which species below has the LOWEST Janka hardness?

• ABlack walnut
• BRed oak
• CHard maple
• DHickory

The Janka hardness test measures:

• AThe compressive strength of wood parallel to the grain
• BThe force required to embed a 0.444-inch steel ball to half its diameter into the wood
• CThe moisture content at which fiber saturation occurs
• DThe shrinkage coefficient from green to oven-dry

The distinctive ray-fleck figure prized in some floors is most pronounced in:

• APlain-sawn red oak
• BQuarter-sawn white oak
• CRift-sawn maple
• DLive-sawn walnut

Which grading factor would NOT normally be considered a manufacturing defect in NOFMA/NWFA-style grading of solid strip oak flooring?

• AKnots within allowable size and count for the grade
• BSaw marks or chatter on the face from the milling machine
• CMis-milled tongue and groove that does not engage
• DMissing endmatch profile

Sapwood is generally allowed without restriction in which grade of solid oak flooring?

• AClear/Select
• B#1 Common
• C#2 Common
• DCharacter/Tavern

Hard maple is most often used in which type of flooring application?

• AExterior decking
• BGymnasium and bowling alley floors
• CBelow-grade wood floors
• DMarine plywood subflooring

Which of the following best describes plain-sawn (flat-sawn) lumber?

• AGrowth rings nearly parallel to the face of the board
• BGrowth rings perpendicular to the face of the board
• CGrowth rings at 30–60 degrees to the face of the board
• DNo discernible grain pattern

Tangential shrinkage in wood — relative to radial shrinkage — is approximately:

• AAbout one-half as much
• BAbout the same
• CRoughly twice as much
• DRoughly four times as much

Which species is most likely to display significant color change (yellowing or ambering) over time when exposed to UV light?

• ABrazilian cherry (jatoba)
• BHard maple
• CBlack walnut
• DHickory

Which is true of red oak compared with white oak for flooring use?

• ARed oak has tyloses-filled pores making it more water resistant
• BRed oak is harder than white oak
• CRed oak is more open-grained and absorbs stain more aggressively
• DRed oak is generally darker than white oak in natural color

An inspector finds severe color and grain mismatch across a quarter-sawn white oak floor installed from a single lot. The MOST likely cause is:

• AManufacturer milling defect
• BNatural color and ray-fleck variation inherent in quarter-sawn white oak
• CUV exposure causing photo-darkening
• DInstaller failure to acclimate the boards

What is the defining structural feature of engineered hardwood flooring?

• AA single thick piece of solid wood, identical to traditional hardwood
• BMultiple layers (typically plywood or HDF core) topped with a real wood veneer wear layer
• CA printed paper decor layer over an HDF core with a melamine wear surface
• DLayers of PVC with a printed film and clear vinyl wear layer

Laminate flooring is constructed of:

• AA real wood veneer over a plywood core
• BA photographic decor layer over an HDF core, topped with a melamine wear layer
• CPVC core with a printed film and clear wear layer
• DSolid linoleum laminated to a fiberboard backing

Luxury vinyl plank (LVP) flooring is primarily composed of:

• AA solid wood veneer bonded to PVC
• BMultiple layers of PVC with a printed film decor and a clear vinyl wear layer
• CAn HDF core with a paper decor and melamine wear layer
• DCork backing with a printed paper wear surface

The 'wear layer' on engineered hardwood refers to:

• AThe melamine coating on top of the decor paper
• BThe thickness of the real wood veneer above the core
• CThe clear vinyl topcoat over the printed film
• DThe factory-applied stain coat

Which flooring product can typically be sanded and refinished MULTIPLE times?

• ALaminate
• BLVP
• CSolid 3/4-inch hardwood
• DFoam-backed underlayment

An engineered floor with a 1 mm hardwood veneer wear layer can typically be sanded and refinished:

• A10 or more times, like solid hardwood
• BGenerally not at all — light screen and re-coat only
• COnce, removing approximately 0.5 mm of veneer
• DFive or six times

Which installation method requires that the flooring be mechanically fastened to a wood subfloor with cleats or staples?

• AFloating click-lock
• BNail-down (or staple-down)
• CFull-spread glue-down
• DLoose-lay

A 'floating floor' installation means:

• AThe floor is loosely nailed at the perimeter only
• BBoards interlock or are glued edge-to-edge but are NOT fastened to the substrate
• CThe floor is installed over a waterproof membrane in slab depressions
• DThe boards are suspended on adjustable pedestals above the subfloor

Which installation method is generally REQUIRED for direct-glue-down engineered hardwood over concrete?

• ANail-down with concrete nails
• BFloating over foam underlayment
• CFull-spread adhesive recommended by the flooring manufacturer, with a moisture mitigation…
• DMechanical screw-down through the tongue

Parquet flooring is characterized by:

• ALong strip planks installed parallel to the long wall
• BGeometric patterns assembled from short wood pieces (slats, blocks, or tiles)
• CPhotographic decor printed onto HDF tiles
• DPVC tiles printed in geometric patterns

Click-lock laminate planks are designed to be installed:

• AGlue-down to the subfloor over a hot-melt adhesive
• BNailed through the tongue every 8 inches
• CAs a floating floor with foam underlayment and an expansion gap at all vertical obstructi…
• DDirectly over carpet without underlayment

Which best describes the 'aluminum oxide' commonly listed in factory-finished wood floor specifications?

• AA ceramic abrasive embedded in the UV-cured finish to increase wear resistance
• BA natural mineral coloring used to stain oak floors
• CAn adhesive used to bond engineered ply layers
• DA vapor barrier installed under wood floors

Engineered hardwood is generally MORE dimensionally stable than solid hardwood primarily because:

• AEngineered hardwood has thinner boards
• BThe cross-banded core layers run perpendicular to each other, restraining seasonal moveme…
• CEngineered flooring contains no real wood
• DEngineered hardwood is sealed with paint instead of polyurethane

Which product type is generally MOST tolerant of high humidity and minor moisture exposure?

• ASolid 3/4-inch hardwood
• BLaminate with HDF core
• CLVP (luxury vinyl plank)
• DParquet over plywood

An inspector finds catastrophic edge swelling on a click-lock laminate floor near a refrigerator water-line leak. The MOST likely failure mode is:

• AUV photo-darkening of the decor layer
• BHDF core absorbed water, swelled, and lifted the planks at the joints
• CVinyl wear layer separation from the PVC core
• DTongue and groove tannin reaction with the moisture barrier

Which of the following is a primary purpose of cross-banding the plies of engineered hardwood flooring?

• ATo make the boards lighter for shipping
• BTo restrain wood movement in two directions and improve dimensional stability
• CTo allow the floor to conduct heat better for radiant systems
• DTo reduce material cost by using thinner veneer

What is equilibrium moisture content (EMC) in wood flooring?

• AThe maximum moisture wood can hold before fiber saturation
• BThe moisture content at which wood neither gains nor loses moisture to the surrounding ai…
• CThe moisture content required for the adhesive to fully cure
• DThe moisture content at the time of milling at the factory

What is the NWFA target relative humidity range for typical interior service conditions for installed wood flooring?

• A10–25%
• B30–50%
• C55–75%
• D75–90%

Within the NWFA-recommended 30–50% RH service range, installed wood flooring typically has an EMC of approximately:

• A2–4%
• B6–9%
• C12–15%
• D18–22%

Cupping in a wood floor is BEST described as:

• AA convex (high-center) deformation across the width of a board
• BA concave (high-edges, low-center) deformation across the width of a board
• CLengthwise warping along the entire board
• DA gap between adjacent boards along their edges

Crowning across a wood floor most commonly results from:

• ASubfloor moisture entering from below for the first time
• BMoisture entering from above the floor (such as a wet-mop habit) OR sanding a cupped floo…
• CInsufficient nail fastening at the manufacturer's prescribed schedule
• DUsing a UV-cured factory finish in a humid climate

Gapping between solid hardwood boards is most commonly observed:

• AIn the summer when humidity is highest
• BIn the winter when interior heating dries the air and reduces RH
• CImmediately after installation in any season
• DWhen the subfloor remains saturated

Buckling (or tenting) of a wood floor is BEST described as:

• ABoards lifting off the subfloor, often along a single seam, due to severe lateral compres…
• BBoards developing a permanent concave cup
• CBoards developing a permanent convex crown
• DBoards shrinking until they fall through the joists

ASTM F1869 measures concrete subfloor moisture by:

• AInserting a probe into a hole drilled to 40% slab depth
• BSealing a dish of anhydrous calcium chloride to the slab surface for 60–72 hours and weig…
• CApplying a polyethylene sheet overnight and observing condensation
• DReading a non-invasive capacitance meter on the slab surface

ASTM F2170 measures concrete subfloor moisture by:

• ASealing a calcium chloride dish to the slab surface
• BDrilling a hole and inserting an in-situ RH probe at 40% of the slab depth (or 20% on sla…
• CCutting a 1-foot square sample of slab and oven-drying it
• DMeasuring slab pH with a phenolphthalein test strip

A common ASTM F1869 limit for installing moisture-sensitive flooring over concrete is approximately:

• A3 lb/1,000 sq ft / 24 hr
• B12 lb/1,000 sq ft / 24 hr
• C30 lb/1,000 sq ft / 24 hr
• DThere is no published limit

A common ASTM F2170 in-situ RH ceiling for installing moisture-sensitive flooring over concrete is approximately:

• A35%
• B50%
• C75%
• D95%

NWFA installation guidelines specify that the moisture content of solid strip flooring should be within how many percentage points of the moisture content of a wood subfloor at the time of installation?

• A0.5%
• B2%
• C4%
• D10%

How many moisture readings does the NWFA recommend taking on a typical 1,000 sq ft solid strip wood floor at installation?

• AApproximately 4 readings
• BApproximately 10 readings
• CApproximately 40 readings
• DOne reading per room is sufficient

An inspector documents 65% RH and 80°F in a home for several months. Based on the Wood Handbook EMC tables, the likely equilibrium moisture content of the installed wood floor is approximately:

• AAround 4% MC
• BAround 7% MC
• CAround 12% MC
• DAround 22% MC

An installer reports the slab tested at 70% RH per ASTM F2170 and 4 lb MVER per ASTM F1869, but the engineered hardwood manufacturer's spec is 75% RH and 3 lb MVER. The installer proceeds. The MOST defensible inspector conclusion is:

• AInstallation is within specification because the RH was below 75%
• BInstallation is within specification because the MVER was within rounding error
• CThe installation exceeded the manufacturer's MVER limit; the installer failed to honor th…
• DASTM tests are advisory only and do not override the installer's judgment