1 Scope
NOTE This standard governs the materials and installation of interior wood finish flooring — solid strip and plank, engineered multi-ply flooring, wood parquet tile and block, and end-grain block — installed over wood and concrete substrates in commercial and institutional construction. (1.1)
NOTE Wood flooring is specified where the appearance, warmth, resilience, or sports performance of a real wood surface is required: corridors, offices, classrooms, lobbies, gymnasiums and multipurpose rooms, residential units within commercial projects, and specialty commercial spaces. (1.2)
NOTE Unlike a manufactured floor covering laid down as a finished sheet, a wood floor is a hygroscopic natural material that gains and loses moisture with its surroundings and changes dimension as it does; its long-term performance is inseparable from the moisture condition of the substrate, the acclimation of the wood, and the building's ability to hold a stable interior climate. (1.3)
NOTE A wood floor is a system of substrate, attachment, wood, and finish, not a single product. (1.4)
NOTE It consists of the prepared and tested subfloor, any required vapor retarder or sleeper assembly, the attachment medium (fasteners or adhesive), the wood flooring itself, and the finish — factory-applied or field-applied — together with perimeter expansion provisions, transitions, and the maintenance regime that preserves it. (1.5)
1.6The Contractor shall verify that the wood flooring, the adhesive or fasteners, and the moisture-control measures are compatible with the measured substrate condition and with one another.
1.7The Contractor shall not begin installation until the substrate, the ambient conditions, and the wood have met the moisture and acclimation acceptance criteria of this standard.
NOTE The species, grade, dimensions, attachment method, and finish are selected together for the service the floor must survive — a wide solid plank that performs in a stable, conditioned residence will cup and gap in a high-traffic lobby with swinging humidity, where a narrow engineered product is required. (1.10)
NOTE The dominant causes of wood flooring failure are moisture-related — installation over a wet or untested slab, installation of wood that was not acclimated to its in-service moisture content, and operation of the building outside the humidity band the floor was specified for; all three are preventable and all three are controlled before and during installation, not after. (1.11)
2 Referenced Standards
| Standard |
Title |
| NWFA Installation Guidelines |
Wood Flooring Installation Guidelines (2025 revision) |
| NWFA/NOFMA Unfinished |
Grading and Manufacturing Standards for Unfinished Solid Wood Flooring (2018 revision) |
| NWFA/NOFMA Factory Finished |
Grading and Manufacturing Standards for Factory Finished Solid Wood Flooring (2019 revision) |
| ANSI/HPVA EF 2020 |
American National Standard for Engineered Wood Flooring (Decorative Hardwoods Association) |
| MFMA Grading Rules |
Maple Flooring Manufacturers Association Grading Rules for Northern Hard Maple, Beech, and Birch |
| ASTM D2394 |
Test Methods for Simulated Service Testing of Wood and Wood-Based Finish Flooring |
| ASTM F1667 |
Specification for Driven Fasteners: Nails, Spikes, and Staples |
| ASTM F1869 |
Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride |
| ASTM F2170 |
Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes |
| ASTM F2772 |
Standard Specification for Athletic Performance Properties of Indoor Sports Floor Systems |
| IBC |
International Building Code, Chapter 23 — Wood (current adopted edition) |
2.1All materials, testing, and installation shall comply with the latest edition adopted by the Authority Having Jurisdiction for each of the standards listed, unless a specific edition is cited.
2.2Where the contract documents, a referenced standard, or the flooring manufacturer's written instructions impose a more stringent requirement than the minimum of any other standard, the more stringent requirement governs unless the Architect of Record directs otherwise in writing.
2.3The Contractor shall follow the manufacturer's written installation instructions in addition to this standard.
NOTE As with all field-installed wood finishes, the manufacturer's written installation instructions define the conditions under which the product warranty is valid; an installation that departs from them — wrong adhesive, wrong fastener, wrong substrate, or wrong moisture condition — voids the warranty regardless of workmanship quality. (2.4)
NOTE The NWFA Installation Guidelines are the de facto industry installation reference, universally accepted by manufacturers; the NWFA/NOFMA standards define the grade of unfinished and factory-finished solid hardwood; ANSI/HPVA EF 2020 is the governing product standard for engineered wood specifically, defining veneer thickness, the three-cycle-soak bond-line delamination test, moisture content, and machining tolerances; and the MFMA rules together with ASTM F2772 govern the specialty case of maple gymnasium sports floors. (2.5)
3 Submittals
3.1 Action Submittals
3.1.1The Contractor shall submit the following for the Architect's review prior to procurement and installation:
- Product data for the wood flooring, identifying species (by botanical name where ambiguous), grade and the governing grading standard, nominal thickness and face width, edge and end profile, wear-layer (veneer) thickness for engineered products, factory finish or unfinished, and the manufacturer's written installation instructions
- Product data for the adhesive, fasteners, vapor retarder, underlayment, sound-control mat, and any moisture-mitigation or sleeper components, demonstrating compatibility with the wood flooring and the substrate
- Substrate moisture test reports for the actual subfloor — wood moisture content for wood subfloors, and ASTM F2170 in-situ relative humidity (and ASTM F1869 emission rate where used) for concrete slabs — identifying test locations, ambient conditions, and dates
- Samples of the wood flooring showing the specified species, grade, surface texture, finish, and the natural range of color and grain to be expected
- For site-finished work, samples of the finished floor showing the specified stain color, finish type, and sheen
- For gymnasium maple sports floors, MFMA grade certification, the floor-system performance class, and ASTM F2772 performance test data for the proposed system
- Maintenance instructions identifying approved cleaning agents and the recoat or refinish compatibility of the delivered finish
☐ Product data — wood flooring (species, grade, dimensions, profile, finish)
☐ Product data — adhesive, fasteners, vapor retarder, underlayment, sound mat
☑ Substrate moisture test reports (wood MC; F2170 / F1869 for concrete)
☐ Samples — species, grade, texture, finish, color/grain range
☐ Site-finish samples (stain color, finish type, sheen)
☐ Gymnasium: MFMA certification + ASTM F2772 performance data
☐ Maintenance instructions (cleaning + recoat compatibility)
3.1.2Installation shall not begin until the substrate moisture test reports have been submitted and reviewed.
NOTE The substrate moisture condition determines whether the specified product and attachment method are appropriate at all, and whether a moisture-mitigation measure is required; it is the gating submittal. (3.1.3)
3.2 Closeout Submittals
3.2.1The Contractor shall provide the following at project closeout:
- Manufacturer product warranty documentation executed in the Owner's name
- Record of the final substrate moisture test results, the wood moisture content at installation, the acclimation period and conditions, and the attachment method and adhesive or fastener actually used, retained for warranty purposes
- For gymnasium sports floors, the ASTM F2772 field or certified performance test results and the game-line layout record
- Maintenance materials transmittal documenting attic stock, touch-up, and finish material delivered to the Owner
☑ Manufacturer product warranty (executed in Owner's name)
☐ Record of substrate moisture, wood MC, acclimation, attachment method
☐ Gymnasium: ASTM F2772 performance results + game-line layout record
☐ Maintenance materials transmittal (attic stock, touch-up, finish)
4 Quality Assurance
4.1 Installer Qualifications
○ NWFA Certified Installer (or manufacturer-certified for the specified system)
● Experienced commercial wood flooring installer (documented comparable projects)
○ MFMA / sports-floor certified installer (gymnasium maple systems)
4.1.1Wood flooring shall be installed by an installer with documented experience installing the specified product type, attachment method, and finish on commercial projects of comparable size and complexity.
4.1.2Gymnasium maple sports floors shall be installed by an installer certified or approved by the sports-floor system manufacturer.
NOTE A wood floor is fitted, fastened or bonded, and on site-finished work sanded and finished by hand, and the cured result reflects the installer's judgment about acclimation, fastening schedule, expansion gaps, and moisture readings that cannot be inspected or corrected after the floor is down and finished. (4.1.3)
4.2 Mock-Up
○ Yes — install a representative area including a transition and, for site-finish, the finish system
● No
4.2.1Where a mock-up is required, the Contractor shall install a representative area of the complete floor at a location directed by the Architect, including a perimeter expansion detail and a transition to an adjacent finish, and for site-finished work the full sealer, stain, and finish system.
4.2.2The mock-up shall remain available for comparison throughout the work and shall establish the acceptable standard for color and grain range, surface texture, stain color, sheen, and joint tightness.
NOTE Wood is a natural material with an inherent color and grain range within any grade; the mock-up sets the Owner's and Architect's expectation for that range so that natural variation is not later rejected as a defect. (4.2.3)
4.3 Pre-Installation Conference
4.3.1Before installation begins, the Contractor shall hold a pre-installation conference with the Architect, the flooring installer, the concrete or framing subcontractor, and the mechanical contractor responsible for building conditioning, to review the moisture test results, the acclimation plan, the HVAC startup sequence, the substrate preparation and flatness, the attachment method, the expansion provisions, the finish schedule, and the protection plan.
4.3.2The HVAC shall be operational and the interior climate stabilized to the in-service range before the wood is delivered, acclimated, and installed.
NOTE The single most consequential coordination item is building conditioning; the conference exists to confirm that the mechanical and finishes schedules support that sequence rather than collide with it. (4.3.3)
5 Acclimation and Service Conditions
5.1 Building Conditioning Before Installation
5.1.1The permanent HVAC system shall be operational and the interior temperature and relative humidity stabilized to the expected in-service range before wood flooring is delivered to the project, throughout acclimation and installation, and continuously thereafter.
3055
303540455055
Default: 45 % RH
5.1.2The interior shall be maintained between 60 °F and 80 °F and within a relative humidity band of approximately 35% to 55% during acclimation and installation, and the building shall be operated to hold that band in service.
NOTE Wood reaches an equilibrium moisture content set by the surrounding temperature and humidity; if the floor is installed into a dry, unconditioned shell and the building is later humidified, the boards swell and buckle, and if installed into a humid shell that is later dried, they shrink and gap. Stabilizing the climate before installation is what makes the wood's installed moisture content match its in-service moisture content. (5.1.3)
5.2 Wood Acclimation
3-5 days (engineered, stable jobsite conditions)
5-7 days (engineered or solid, typical)
7-14 days (solid, wide plank, or large moisture differential)
Until wood MC is verified within tolerance of subfloor MC (no fixed period)
5.2.1Wood flooring shall be acclimated on the conditioned jobsite until its moisture content reaches equilibrium with the in-service environment and is within the tolerance of this standard relative to the subfloor.
5.2.2Acclimation shall be verified by moisture meter readings of the flooring and the subfloor, not by elapsed time alone.
5.2.3Flooring shall be broken out of its packaging or cross-stacked with spacers as the manufacturer directs so that air can reach all surfaces during acclimation.
NOTE A fixed number of days is a planning estimate, not an acceptance criterion: the floor is acclimated when its measured moisture content is in equilibrium with the conditioned space, which depends on species, thickness, board width, and how far the delivered wood was from equilibrium. Wide and thick solid boards take longest; engineered products, being dimensionally more stable, take least. (5.2.4)
5.3 Wood and Subfloor Moisture Content
24
24
Default: 2 percentage points
5.3.1Solid wood flooring shall be installed at a moisture content between 6% and 9% per the NWFA Installation Guidelines, and engineered flooring at the moisture content stated by its manufacturer under ANSI/HPVA EF 2020, generally also 6% to 9%.
5.3.2The wood subfloor moisture content shall not exceed 12%.
5.3.3The moisture content differential between solid strip flooring and the wood subfloor shall not exceed 2 percentage points, and for plank 3 inches and wider shall not exceed 2 percentage points unless the manufacturer permits otherwise.
5.3.4The Contractor shall measure and record the moisture content of both the flooring and the subfloor at multiple representative locations before installation.
NOTE A large moisture differential between the floor and the subfloor guarantees movement after installation as the two equalize: a floor drier than its subfloor will absorb moisture and cup or buckle, and a floor wetter than its subfloor will release moisture and gap. The differential limit, not the absolute reading alone, is what protects against post-installation movement. (5.3.5)
5.4 Concrete Slab Moisture
5.4.1The acceptable concrete substrate moisture condition is a governing service condition for wood flooring and shall be established by test before installation and confirmed against the lower of the system manufacturer's limit and the limit of this standard.
7090
7075808590
Default: 75 % RH
35
35
Default: 3 lb/1000 sq ft/24 hr
5.4.2The relative humidity within the concrete slab, measured by in-situ probe per ASTM F2170 at 40% of the slab depth for slabs drying from one side, shall not exceed the limit stated without a moisture-mitigation measure rated for the actual reading.
5.4.3Where moisture vapor emission rate is used as a screening or supplementary measure per ASTM F1869, the rate shall not exceed 3 lb/1000 sq ft/24 hr for most adhesive glue-down, or 5 lb where a urethane adhesive with an integral moisture-control limit is specified.
NOTE Failure to test the slab — or testing only with the surface calcium chloride method on a slab on or below grade — is the single largest cause of adhesive failure, cupping, and delamination claims, because a slab interior can remain wet long after the surface reads dry. ASTM F2170 internal relative humidity is the reliable measure for slabs on or below grade. (5.4.4)
6 Wood Flooring Products
6.1 Product Type
NOTE The product type is the foundational selection; it determines which substrates and attachment methods are available, the achievable board width, the dimensional stability, and the refinishing lifecycle. (6.1.1)
Solid strip flooring (tongue-and-groove, face width 3 in or less)
Solid plank flooring (tongue-and-groove, face width over 3 in)
Engineered multi-ply strip flooring (hardwood face veneer)
Engineered multi-ply plank flooring (hardwood face veneer)
Wood parquet tile / block (finger block or pattern)
Maple gymnasium sports floor (over resilient sleeper system)
End-grain wood block (industrial / specialty)
Per drawings
6.1.2The product type shall be selected for the substrate, the climate stability of the space, and the attachment method, and shall be indicated in the finish schedule. NOTE Solid wood is milled from a single piece of hardwood and can be sanded and refinished many times, but it moves the most with humidity and is restricted to above-grade wood subfloors or to sleeper assemblies over concrete; it is not appropriate directly on or below grade. Engineered flooring is built up from a hardwood face veneer over a cross-laminated plywood or HDF core, which dramatically reduces dimensional movement and allows installation over concrete on and above grade by glue-down or floating; its refinishing lifecycle is limited by the veneer thickness. Parquet is small finger blocks or patterned pieces, usually glued down. Maple gymnasium floors are a specialty assembly of solid hard maple over a sprung or pad-and-sleeper system engineered for athletic performance. End-grain block, set with the grain vertical, is an industrial wearing surface, not a typical commercial finish. (6.1.3)
6.2 Species and Hardness
Red oak (domestic, Janka ≈1290 lbf)
White oak (domestic, Janka ≈1360 lbf)
Hard (sugar) maple (domestic, Janka ≈1450 lbf)
Hickory / pecan (domestic, Janka ≈1820 lbf)
Ash (domestic, Janka ≈1320 lbf)
American walnut (domestic, Janka ≈1010 lbf)
Specified imported/exotic species (by botanical name, Janka per submittal)
Per drawings
10001820
10101290136014501820
Default: 1290 lbf
6.2.1The species shall be selected for the hardness, dimensional stability, appearance, and cost appropriate to the application, and shall be specified by name and minimum Janka hardness.
6.2.2Imported and exotic species shall be specified by botanical name in addition to any common or trade name.
NOTE Janka hardness measures resistance to denting and wear and should be matched to traffic: red oak at about 1290 lbf is the residential and light-commercial benchmark, hard maple at about 1450 lbf is preferred for heavy commercial corridors and retail, and gymnasium floors use northern hard maple graded under the MFMA rules. Common names are ambiguous — "Brazilian cherry" alone can denote more than one species with different hardness and stability — so specifying the botanical name or a minimum Janka value prevents a substitution that looks similar but performs differently. (6.2.3)
6.3 Grade
Clear / Premier (most uniform color and grain, fewest character marks)
Select and Better (limited character marks)
No. 1 Common / Character (moderate color variation and character marks)
No. 2 Common / Rustic (pronounced variation, knots, and character marks)
Per drawings
6.3.1The flooring grade shall be specified by reference to the governing grading standard — NWFA/NOFMA for solid hardwood, ANSI/HPVA EF 2020 for engineered — not by a trade grade name alone.
NOTE Grade governs the permitted amount of color variation, sapwood, knots, and other character marks, not the structural quality of the wood: a Clear grade is the most uniform, while No. 2 Common (Rustic) deliberately shows pronounced variation and character. Grade nomenclature is not interchangeable between standards — NWFA/NOFMA "Clear" is not the same definition as an ANSI/HPVA EF 2020 A-Grade, and each manufacturer's proprietary grade names map differently again — so the specification must name the standard the grade is measured against. (6.3.2)
6.4 Dimensions and Profile
3/4 in (solid strip/plank; heavy-duty engineered)
1/2 in (engineered plank, typical commercial)
3/8 in (engineered or thin solid)
5/16 in (thin solid / parquet)
Per drawings
2-1/4 in (standard strip)
3 in (narrow plank)
5 in (plank)
7 in (wide plank)
Over 7 in (wide plank, engineered recommended)
Per drawings
○ Tongue-and-groove, end-matched (T&G all four edges)
○ Tongue-and-groove, square edge (no microbevel)
● Tongue-and-groove, micro-beveled / eased edge
○ Click-lock profile (engineered floating)
6.4.1The nominal thickness, face width, and edge and end profile shall be as specified and coordinated with the attachment method and the refinishing expectation.
NOTE Wider boards move more across their width with the same change in moisture content than narrow boards do, so wide solid plank is more prone to visible gapping and cupping and is more reliably delivered as an engineered product; thickness governs both the available attachment method (3/4-inch product accepts cleats and staples; thinner solid takes finer staples) and how many times a floor can be resanded. A micro-beveled edge hides minor height variation between boards and is common on prefinished flooring; a true square edge yields a flush, monolithic surface but demands a flatter substrate and is typical of site-finished work. (6.4.2)
6.5 Engineered Wear Layer
2 mm (light residential, not refinishable)
3 mm (commercial, one light resand)
4 mm (commercial, refinishable)
6 mm (heavy commercial, two-sand lifecycle)
Per drawings
6.5.1For engineered flooring, the hardwood face veneer (wear layer) thickness shall be specified per ANSI/HPVA EF 2020 for the intended refinishing lifecycle.
NOTE The wear layer is the only part of an engineered board that can be sanded; a 2 mm veneer is essentially never refinishable, 3 mm to 4 mm permits one to two light resands over a commercial lifecycle, and 6 mm supports a genuine two-sand lifecycle approaching that of solid flooring. Specifying a thin wear layer for a floor expected to be refinished is a false economy that forces a full replacement when the floor wears. (6.5.2)
6.6 Surface Texture
● Smooth / flat (sanded)
○ Wire-brushed (open grain, hides wear)
○ Hand-scraped (artisan texture)
○ Skip-sawn / distressed
Per drawings
6.6.1The surface texture shall be as selected and consistent with the finish and grade.
NOTE A smooth, flat surface is the conventional commercial and institutional finish; wire-brushing opens the grain and is effective at hiding scuffs and wear in high-traffic areas; hand-scraped and skip-sawn textures are appearance choices that read as rustic or artisan. Texture is largely an appearance and wear-concealment decision and does not change the wood's structural performance. (6.6.2)
7 Attachment and Substrate
7.1 Attachment Method
Nail / cleat-down (wood subfloor only)
Staple-down (wood subfloor only)
Full-spread adhesive glue-down (concrete or wood)
Floating, glued tongue-and-groove (engineered)
Floating, click-lock (engineered)
Per drawings
7.1.1The attachment method shall be compatible with both the product type and the substrate, and shall be indicated on the finish schedule. 7.1.2Floating installation shall be used only with engineered products designed for it, not with solid 3/4-inch flooring.
7.1.3Nail- and staple-down attachment requires a wood subfloor; nail- or staple-down attachment shall not be specified over a bare concrete slab unless a wood sleeper assembly or nailable underlayment over a vapor retarder is provided.
NOTE Each attachment method suits a different combination of product and substrate: nail- and staple-down fastens solid (and some engineered) flooring through the tongue into a wood subfloor and is the traditional method for solid 3/4-inch product; full-spread glue-down bonds the flooring to concrete or wood with adhesive and is the common method for engineered flooring and parquet over slabs; floating leaves the flooring unattached to the substrate, joined only at its edges by glue or a click profile, riding on an underlayment, and is limited to engineered products. Specifying floating for solid strip, or nail-down without providing the wood substrate it requires, is a common error that voids the manufacturer warranty and creates a scope gap between the finish and the substrate trades. (7.1.4)
7.2 Fasteners (Nail/Staple-Down)
16-gauge cleats, 1-3/4 in to 2 in (solid 3/4 in)
15.5-gauge staples, 1-3/4 in to 2 in (solid 3/4 in)
18-gauge staples, 1-1/2 in (3/8 in to 1/2 in solid/engineered)
7.2.1Fasteners for nail- and staple-down installation shall conform to ASTM F1667 and shall be the type and size matched to the flooring thickness per the NWFA Installation Guidelines.
7.2.2For solid 3/4-inch flooring, cleats or staples shall be installed at 6 in to 8 in along each board and within 1 in to 3 in of each board end, with additional fasteners as the board length and width require.
NOTE Fastener size is correlated to flooring thickness: 16-gauge cleats or 15.5-gauge staples 1-3/4 in to 2 in long for solid 3/4-inch product, and finer 18-gauge staples 1-1/2 in long for 3/8-inch to 1/2-inch material. An undersized or under-spaced fastening schedule lets boards move and squeak; an oversized fastener can split the tongue. (7.2.3)
7.3 Adhesive (Glue-Down)
Urethane (full-spread, moisture-tolerant)
MS polymer / silane-modified (full-spread, low-VOC)
Epoxy (specialty / high-strength)
Pressure-sensitive (parquet / repositionable only)
○ 3/32 in V-notch
● 1/8 in V-notch
○ 1/4 in square notch (per adhesive manufacturer)
7.3.1The adhesive shall be a full-spread urethane or MS-polymer adhesive for commercial glue-down installations, applied with the trowel notch and at the spread rate the adhesive manufacturer specifies for the flooring.
7.3.2Pressure-sensitive adhesive shall not be used for full-spread plank glue-down in commercial traffic.
7.3.3The adhesive shall be compatible with the flooring and, where the slab moisture approaches the limit, shall be a moisture-control adhesive rated for the measured condition.
NOTE Commercial glue-down demands a full-spread urethane or MS-polymer adhesive: these cure to a strong, slightly flexible bond, tolerate slab moisture better than other chemistries, and many include an integral moisture and crack-isolation function. Pressure-sensitive adhesive is repositionable and appropriate for parquet or tile but does not develop the bond a plank floor needs under rolling and foot traffic. Spread rate matters — too little adhesive starves the bond and leaves hollow spots, too much squeezes onto the face — so the specified trowel notch, typically a 3/32 in or 1/8 in V-notch yielding roughly 40 to 60 sq ft per gallon, is part of the requirement. (7.3.4)
7.4 Substrate Type and Vapor Retarder
Wood structural panel subfloor (above grade)
Concrete slab, above grade
Concrete slab, on grade
Concrete slab, below grade
Per drawings
● None required (wood subfloor, or slab passes within limits)
○ Vapor retarder sheet under wood subfloor / sleepers (asphalt-laminated kraft or poly)
○ Penetrating moisture-control sealer on slab
○ Moisture-control membrane or moisture-control adhesive (rated for measured RH)
Per drawings
7.4.1The substrate type shall be identified and, where it is concrete on or below grade, the product and attachment method shall be limited to engineered or to a sleeper assembly, with the moisture-mitigation measure selected for the measured slab condition.
7.4.2Where solid wood flooring is installed over concrete, a wood sleeper system or nailable subfloor over a vapor retarder shall be provided, and the vapor retarder and sleeper assembly shall be detailed on the details. 7.4.3Where the slab relative humidity exceeds the flooring or adhesive limit, the moisture-mitigation product shall be rated for the RH actually measured, not a generic value.
NOTE Solid wood directly bonded to on-grade or below-grade concrete is outside its appropriate use; either an engineered product is specified, or a raised sleeper assembly over a vapor retarder is built to create the wood substrate and the air space solid flooring requires. Where a mitigation measure is installed, the product must be matched to the measured slab RH, not selected generically. (7.4.4)
7.5 Subfloor Flatness
● 3/16 in in 10 ft (nail/staple-down and glue-down)
○ 1/8 in in 10 ft (floating installation)
Per drawings
7.5.1The subfloor shall be flat within 3/16 in in 10 ft for nail-, staple-, and glue-down installation, and within 1/8 in in 10 ft for floating installation, per the NWFA Installation Guidelines.
7.5.2High and low spots beyond the tolerance shall be ground down or filled with a compatible patching or self-leveling compound before installation.
NOTE A floating floor is least forgiving of an out-of-flat subfloor because it is not held down to follow the substrate; unsupported humps and hollows let the floor flex underfoot, telegraph as hollow spots, and stress the edge joints. Glue-down and nail-down are somewhat more tolerant but still require the stated flatness to bond and fasten uniformly. (7.5.3)
8 Finish
8.1 Finish Type
● Factory prefinished (aluminum-oxide UV-cured)
○ Site-finished (sealer and finish applied after installation)
Per drawings
8.1.1The finish type shall be specified as factory-prefinished or site-finished, and the choice shall be coordinated with the construction sequence and the other finish trades.
NOTE Site-finished flooring requires the floor to be clear of millwork toe-kicks, cabinetry, and traffic during sanding and finishing; specifying a site finish where casework is already installed creates a coordination conflict. (8.1.2)
NOTE The two finish approaches drive sharply different coordination. A factory-prefinished floor arrives with a tough, aluminum-oxide UV-cured finish already cured under factory conditions and is walkable as soon as it is installed, eliminating jobsite sanding dust, odor, and downtime, but its micro-beveled edges and fixed color are the price. A site-finished floor is installed raw and then sanded flat and sealed, stained, and finished in place, yielding a smooth monolithic surface and any custom color, but it adds days of dust- and odor-generating work that must be sequenced after the floor is clear of other trades and before the space is occupied. The decision belongs early in the finish narrative because it reshapes the whole closeout sequence. (8.1.3)
8.2 Factory Finish
10 years (residential)
15 years (light commercial)
25 years (commercial)
Lifetime (residential, limited)
8.2.1Factory-prefinished flooring shall carry an aluminum-oxide UV-cured finish with a manufacturer wear-through warranty appropriate to the commercial use.
8.2.2The maintenance regime for a prefinished aluminum-oxide floor shall be obtained from the manufacturer, including the compatible recoat finish.
8.2.3The maintenance regime and recoat compatibility information shall be captured in the closeout documents delivered at turnover.
NOTE A prefinished aluminum-oxide finish is extremely abrasion-resistant but cannot be recoated with ordinary oil-modified polyurethane — the new finish will not adhere to the cured aluminum-oxide surface without the manufacturer's prescribed abrasion and tie-coat procedure — so the closeout documents are the only reliable record of the correct recoat procedure once the floor is in service. (8.2.4)
8.3 Site Finish System
Water-based urethane (low odor, fast recoat, color-stable)
Oil-modified urethane (amber tone, durable, slower cure)
Penetrating / hardwax oil (natural matte, spot-repairable)
Per drawings
○ Matte / low-luster (10-20 sheen units)
● Satin (25-35 sheen units)
○ Semi-gloss (55-65 sheen units)
Per drawings
As selected by Architect from manufacturer's standard range, or natural (no stain)
Per drawings
8.3.1Site-finished flooring shall receive the specified sealer, stain (where a stain is specified), and finish system, applied in the number of coats and within the recoat windows the finish manufacturer requires.
8.3.2Satin sheen is the common commercial and institutional default.
8.3.3The finish system shall be selected for durability, color stability, odor and cure time, and maintainability appropriate to the occupancy.
NOTE The finish system is both a wear surface and an appearance choice. Water-based urethane cures fast, has low odor, stays color-stable, and is the common commercial choice where the space must be turned over quickly; oil-modified urethane is durable and inexpensive but ambers over time and cures slowly with strong solvent odor; penetrating and hardwax oils give a natural matte look and are spot-repairable but offer less film protection and need more frequent maintenance. Sheen is a trade-off with how readily the floor shows traffic and scratches: higher gloss reveals every scuff and footprint, which is why satin and matte dominate commercial work. (8.3.4)
9 Special Conditions
9.1 Radiant Heat Compatibility
● No radiant heating
○ Yes - engineered flooring approved for radiant heat
○ Yes - solid flooring (narrow, species- and manufacturer-approved)
Per drawings
9.1.1Where the flooring is installed over an in-floor radiant heating system, the flooring shall be a product the manufacturer approves in writing for radiant heat, and the radiant system shall be limited to a maximum floor surface temperature of 85 °F.
9.1.2Solid flooring over radiant heat shall be limited to narrow widths (3 in or less) of a species and product the manufacturer approves for radiant service.
9.1.3The radiant system shall be operated through a warm-up cycle before installation and the surface-temperature limit shall be maintained in service.
NOTE Radiant heat continuously drives moisture out of the underside of the wood, exaggerating the seasonal shrinkage that causes gapping; engineered flooring, being dimensionally stable, is generally preferred over solid for radiant applications, and where solid is used it must be narrow and species-approved. Exceeding the surface-temperature limit accelerates drying and can scorch the finish, so the limit is a service requirement, not just an installation note. (9.1.4)
9.2 Expansion Provisions
0.50.75
0.50.75
Default: 0.75 in
Per drawings
9.2.1A perimeter expansion gap shall be provided at all walls, doorframes, columns, thresholds, and fixed objects.
9.2.2The perimeter expansion gap shall be sized to match or exceed the flooring manufacturer's requirement, and shall be never less than 3/4 in for 3/4-inch solid flooring or 1/2 in for engineered.
9.2.3The expansion gap shall be concealed by the base, shoe, or threshold and shall never be filled rigidly or omitted.
9.2.4Continuous runs of solid flooring exceeding the manufacturer's maximum unbroken length or width shall be interrupted by an expansion break (a T-molding or expansion joint) so the floor can move without buckling.
NOTE Wood expands and contracts across its width with the seasons, and a floor installed tight to the walls in a continuous large area with no room to grow will swell and buckle in humid weather, lifting off the substrate. The perimeter gap and, in large areas, an intermediate expansion break give the floor the room it must have; omitting or undersizing them is among the most common and most destructive errors. (9.2.5)
9.3 Gymnasium Sports Floors
Anchored resilient (sleeper or channel system, fixed to slab)
Floating resilient (pad-and-sleeper or panel system)
Portable / panel sports floor
Per drawings
○ Class 1 (entry athletic performance)
○ Class 2
● Class 3
○ Class 4 (highest force reduction / area deflection)
Per drawings
9.3.1Gymnasium and multipurpose sports floors shall be northern hard maple graded under the MFMA rules.
9.3.2Gymnasium and multipurpose sports floors shall be installed as a complete resilient sleeper-and-pad system.
9.3.3Gymnasium and multipurpose sports floors shall meet the specified ASTM F2772 athletic performance class for force reduction, ball rebound, area deflection, and surface friction.
9.3.4The sports floor system, its resilient pads, the game-line layout, and the surface finish shall be furnished as a coordinated system from a single manufacturer.
9.3.5Game lines and logos shall be applied per the governing athletic body's layout and within the floor finish system so they wear with the floor.
NOTE A gymnasium maple floor is an engineered athletic system, not just a wood surface: the resilient pads and sprung sleepers give the floor the controlled deflection and shock absorption that protect athletes, and ASTM F2772 grades that performance into classes. Specifying MFMA-certified maple without an ASTM F2772 performance class lets a substandard sleeper system satisfy the letter of the specification while failing the athletic performance the floor exists to provide. (9.3.6)
9.4 Reclaimed and Salvaged Wood
9.4.1Where reclaimed or salvaged wood flooring is specified, the Contractor shall submit the source, the remilling and re-grading basis, the kiln-dried moisture content, and evidence that the material is free of embedded metal, insects, and contaminants, and shall acclimate and test it as for new flooring.
9.4.2The moisture content of reclaimed flooring shall be verified by meter before acclimation begins, because salvaged material arrives at an unknown equilibrium that may differ substantially from kiln-dried new product.
NOTE Reclaimed flooring is within the scope of this standard but the standard NWFA/NOFMA grading rules do not apply directly to it; the NWFA's separate reclaimed-wood guidance and the project-specific grade defined in the submittal govern its appearance, and moisture verification is especially important because the material's equilibration history is unknown. (9.4.3)
10 Installation
10.1 Layout and Substrate Acceptance
10.1.1The Contractor shall not begin installation until the substrate is prepared to the required flatness, the documented moisture tests confirm the substrate and wood are within the governing limits or the specified mitigation is installed, the acclimation is verified by meter, and the ambient conditions are within range.
10.1.2Layout shall establish a straight, square starting line and balance the board courses so that the field is symmetrical and no excessively narrow ripped course occurs at a wall, following the finish plan for direction and any feature or border pattern. NOTE Acceptance of the substrate is the Contractor's responsibility; installing wood flooring over a substrate that is out of tolerance, too wet, or untested transfers a known defect into the finished floor, and the resulting failure is not a product defect and is not covered by the warranty. (10.1.3)
10.2 Installation Execution
10.2.1Flooring shall be installed with end joints staggered and racked for a random distribution of board lengths and a natural blend of the grade's color and grain range.
10.2.2Nail- and staple-down flooring shall be fastened on the specified schedule, blind-nailed through the tongue, with the first and last courses face-nailed or top-nailed and the holes filled where the manufacturer directs.
10.2.3Glue-down flooring shall be set into wet adhesive within the adhesive's working time, fully bedded, and rolled or weighted as the adhesive manufacturer requires to achieve full transfer.
10.2.4Floating flooring shall be installed over the specified underlayment with edge joints glued or clicked per the profile and with the perimeter gap maintained continuously.
NOTE Racking the floor from several open cartons at once blends the natural color and grain variation across the field; installing carton by carton concentrates variation into visible patches that read as a defect even when every board is within grade. (10.2.5)
10.3 Protection During Construction
10.3.1After installation, the floor shall be protected from traffic, point loads, spills, and other trades with a breathable protective covering until turnover, and site-finished floors shall be protected only after the finish has reached the cure the manufacturer requires.
10.3.2A non-breathable plastic film shall not be laid directly over a newly site-finished floor.
NOTE A newly site-finished floor continues to cure and off-gas for days; sealing it under non-breathable plastic traps solvent and moisture against the finish and causes it to cloud or fail to harden, so any covering placed over a fresh finish must be breathable. (10.3.3)
11 Field Inspection
11.1 Moisture and Acclimation Verification
11.1.1The Contractor shall record and retain the substrate moisture readings, the wood moisture content, the acclimation period and conditions, and the ambient temperature and relative humidity at installation as the documented basis for the warranty.
11.1.2Where concrete-slab mitigation was installed, the Contractor shall verify it was rated for the relative humidity actually measured.
11.2.1After installation and, for site-finished work, after the finish has cured, the floor shall be inspected under permanent or equivalent lighting for cupping, crowning, gapping, hollow or loose boards, squeaks, finish uniformity and sheen, color and grain blend, board-end and edge tightness, expansion-gap continuity, and transition quality.
11.2.2Hollow, loose, or squeaking boards shall be corrected by re-fastening, re-bonding, or replacement, and the cause investigated where the condition is widespread.
11.2.3For gymnasium sports floors, the installed system shall be verified against the specified ASTM F2772 performance class before acceptance.
12 Cleaning and Initial Maintenance
12.1After installation and finish cure, the floor shall be cleaned of construction soil using only the cleaning method and products the flooring and finish manufacturers approve, and protected from heavy traffic until turnover.
12.2The Contractor shall furnish the Owner with the manufacturer's maintenance program, identifying approved cleaning agents, the recoat or refinish procedure and compatible finish, and the interior humidity band the floor must be kept within to remain stable.
NOTE Wood floors are damaged by standing water and by cleaners not formulated for wood finishes; a wet-mopping or steam-cleaning regime intended for resilient or tile floors will dull, swell, or delaminate a wood floor, which is why the approved-products maintenance program is part of the deliverable. (12.3)
13 Delivery, Storage, and Handling
13.1Wood flooring, adhesives, and accessories shall be delivered in the manufacturer's original sealed packaging with grade, species, and lot information intact, and shall not be delivered to the project until the building is enclosed, conditioned, and within the acclimation temperature and humidity range.
13.2Flooring shall be stored flat, off the floor, in the conditioned space where it will be installed, protected from moisture, direct sun, and physical damage, and broken out or cross-stacked for acclimation as the manufacturer directs.
13.3Adhesives and water- or solvent-based finishes shall be stored within their temperature range, protected from freezing, and handled per the safety data sheet.
NOTE Delivering wood flooring to an unconditioned or unenclosed building defeats acclimation before it begins: the wood equalizes to the wrong moisture content, and no amount of jobsite time afterward corrects a floor that was wetted on a damp slab or dried in an overheated shell during storage. (13.4)
14 Warranty
1 year (material defects only)
5 years (commercial wear / structural)
10 years (commercial)
25 years (prefinished commercial wear-through)
1 year from substantial completion
2 years from substantial completion
14.1The flooring manufacturer shall warrant the material against manufacturing and grading defects and, for prefinished product, against finish wear-through for the period stated.
14.2The Contractor shall warrant the installation — including substrate preparation, moisture control, acclimation, attachment, expansion provisions, site finish, and transitions — against defective workmanship for the project warranty period.
14.3The moisture and acclimation records are part of the warranty basis and shall be retained and delivered.
NOTE Most manufacturer warranties are void unless the substrate moisture was within the stated limit and the wood was acclimated and installed at the correct moisture content, both documented at the time of installation. Failures arising from operating the building outside the specified humidity band, from water intrusion, or from maintenance contrary to the manufacturer's instructions are excluded from both warranties. (14.4)
15 Spare and Extra Materials
● Yes - sealed flooring and touch-up/finish material for each type and color
○ No
15.1The Contractor shall deliver to the Owner sealed attic stock of each flooring type, species, grade, and color installed, together with touch-up and, for site-finished floors, matching finish material, in a quantity sufficient for localized repair and labeled with the species, grade, color, and lot information.
NOTE Because wood color and grain vary over production runs and a later finish ambers with age, attic stock from the original lot is the only reliable way to make an inconspicuous repair; replacement material bought years later will rarely match the installed floor's color and patina. (15.2)