Hardwood Flooring
Summary
Hardwood flooring is solid wood boards or engineered planks with a hardwood wear layer over a plywood or composite core, installed by nailing, gluing, or floating, factory- or site-finished. It is a warm, refinishable floor, but wood moves with humidity, so moisture control of the subfloor, acclimation, and expansion space decide whether it cups, gaps, or buckles.
Cols
Terminology
- Solid hardwood: one piece of wood through the thickness; 3/4 in. common
- Engineered hardwood: hardwood wear layer bonded to a cross-ply or composite core; more dimensionally stable
- Strip / plank: boards under 3 in. wide, and 3 in. and wider
- Wear layer: hardwood above the tongue; sets how many times a floor can be sanded
- Prefinished / site-finished: factory-applied finish vs. sanded and finished in place
- Cupping / crowning / gapping: distortions from moisture differences across or between boards
- Acclimation: letting flooring adjust to the space's operating temperature and humidity
- Expansion space: gap at walls and fixed objects hidden by base or shoe
- Janka hardness: relative dent resistance of species
- Sleeper system: wood strips over concrete for nailing and ventilation
- Floating floor: planks joined to each other, not fastened to the subfloor
Standards
Ratings
- Moisture difference: NWFA limits flooring-to-subfloor difference to 4 percent for solid strip under 3 in. wide and 2 percent for solid flooring 3 in. and wider; engineered per manufacturer
- Subfloor moisture: 12 percent or less in most regions, within 4 percent of the flooring
- Acclimation: at least five days in the conditioned space is common guidance; moisture meter readings govern
- Concrete slabs: moisture tested per ASTM F2170 or F1869 to the manufacturer's limits
Test standards
- NWFA Installation Guidelines
- ASTM F2170 and F1869: slab moisture
- ASTM E648 / NFPA 253: critical radiant flux where floor finish classification is required
Materials
- Species: red oak, white oak, hard maple, hickory, walnut; white oak and maple for heavy wear
- Solid strip and plank: nail-down over wood subfloors
- Engineered plank: glue-down over concrete, wide planks, and radiant heat
- Finishes: factory UV-cured urethane, site-applied waterborne or oil-modified urethane, hardwax oils
- Underlayments: moisture retarders and acoustic underlayments for multifamily
Detailing
- Keep the building conditioned and dry before delivery; test moisture of flooring and subfloor
- Leave expansion space at walls, columns, and thresholds
- Use engineered flooring over concrete, radiant heat, and in wide planks
- Provide acoustic underlayment in multifamily to meet impact sound targets
- Run boards perpendicular to joists over wood framing where possible
- Detail transitions to tile and resilient floors for level changes
Uses
Specific uses
- Residential living areas and bedrooms
- Hospitality lobbies and guest rooms
- Retail and boutique interiors
- Gymnasium and sports floors (maple systems)
- Offices and conference rooms with residential character
Pros and cons
Pros
- Warm appearance; adds value
- Long life with sanding and refinishing
- Wide species, widths, and finish options
- Engineered planks work over concrete and radiant heat
Cons
- Moves with humidity; cupping and gaps if moisture is not controlled
- Dents and scratches in soft species and high traffic
- Not suited to wet areas
- Impact noise in multifamily without underlayment
Manufacturing and cost
Construction
- Lumber milled to tongue-and-groove profiles; engineered planks laminated to cores
- Installed nailed, stapled, glued, or floated; site-finished floors sanded and coated in place
Main manufacturers and suppliers
- Bruce (AHF Products)
- Mohawk Flooring
- Mirage
- Bona (finishes)
Trade association: National Wood Flooring Association.
Typical costs
- Hardwood flooring, installed: $8 to $28 per sq ft
- Solid red oak strip: $11 to $14 per sq ft installed; solid white oak 5 in. plank: $14 to $18; engineered floating: $7 to $11
Sources
- Weyerhaeuser: managing moisture for hardwood floors (NWFA guidance), https://www.weyerhaeuser.com/blog/manage-moisture-stable-beautiful-hardwood-floors/
- Floor Trends: hardwood installation best practices, https://floortrendsmag.com/articles/104757-hardwood-installation-best-practices
- JLC: controlling the moisture content of wood flooring, https://www.jlconline.com/?p=71880
- Clean Invoice: hardwood flooring cost guide, https://www.clean-invoice.com/en/guides/hardwood-flooring-cost
- Sweets: 09 64 29 wood strip and plank flooring, https://sweets.construction.com/masterformat/finishes-09-00-00/wood-strip-and-plank-flooring-09-64-29
- Wikimedia Commons: Oak herringbone wood floor with two stripe wenge border.jpg, by Pazzo4562 (CC BY-SA 4.0), https://commons.wikimedia.org/wiki/File:Oak_herringbone_wood_floor_with_two_stripe_wenge_border.jpg