Hardwood

Summary

Hardwood is wood from flowering (angiosperm) trees, distinguished from softwood by pores (vessels) and generally slower growth, with Janka hardness ranging from 70 lbf (balsa) to over 5,000 lbf. Species choice sets hardness, decay resistance, and appearance, so specify the species for flooring, millwork, cabinetry, and exterior decking rather than "hardwood" alone.

Cols

Image

Janka hardness: force in lbf to embed an 11.28 mm (7/16 in.) steel ball halfway into the wood; test created by Gabriel Janka (1864 to 1932)
Vessels (pores): water-conducting cells that distinguish hardwood from softwood
Ring-porous / diffuse-porous: pore arrangement (oak, ash, elm / birch, maple, poplar)
Heartwood / sapwood: inner decay-resistant wood / outer less resistant wood
Quartersawn: sawn to show vertical grain lines
Tropical hardwood: dense imported species such as ipê, cumaru, and teak
EAB: emerald ash borer, a beetle killing ash trees

History and demand

First uses in construction

Starting in the late 1960s, New York City used ipê for its boardwalks, eventually converting the whole Coney Island boardwalk (over 10 miles); the original ipê lasted about 25 years

Sourcing

Tropical hardwood logs: Indonesia, India, Viet Nam, Brazil, Thailand, and Malaysia produced about 83 percent of the total in 2021; ITTO members produced about 294 million m3 in 2019 (ITTO)

Demand trend

Teak and mahogany are scarce because of over-exploitation; some wood sold as ipê is mislabeled, and some FSC certificates have been forged
The emerald ash borer has killed at least 50 million ash trees and threatens most ash in North America; hard maple has increasingly replaced white ash in baseball bats

Composition and production

Raw materials

Cellulose, hemicellulose, and lignin (sinapyl and coniferyl alcohols are the main lignin monomers); fewer extractives than softwoods

Product forms

Solid lumber, flooring, veneer, and plywood or MDF faced with hardwood veneer; solid hardwood joinery is costly, so many "hardwood" doors are veneer over a softwood, plywood, or MDF core

Grades and types

Species	Janka (lbf)	Density	Typical building and related uses
White oak	1,360	—	Furniture, floors, building frames, veneers; resistant to insect and fungal attack
Northern red oak	1,290	—	Highly prized for lumber; furniture, floors, veneers
Hard (sugar) maple	1,450	—	Flooring, basketball courts, bowling lanes, musical instruments; valued wavy and birdseye figure
White ash	1,320	About 670 kg/m³ (42 lb/ft³)	Tool handles, bats, furniture, flooring; interior use because it deteriorates in soil contact
Black walnut	1,010	660 kg/m³ (41 lb/ft³)	Furniture, flooring, gunstocks; strong, shock resistant, holds shape after kiln drying
Black cherry	950	About 560 kg/m³ (35 lb/ft³) dried	Premier United States cabinetry timber; veneers and plywood from quartersawn lumber
Yellow poplar	540	About 26.4 lb/ft³ (specific gravity 0.42)	Interior finish, siding clapboards, pattern stock; light, soft, easy to work, stable
Teak	1,155	About 660 kg/m³ (41 lb/ft³) at 15% moisture	Outdoor furniture, boat decks, flooring, countertops, veneer; resists rot, fungi, termites
Ipê (Brazilian walnut)	3,684	Among the hardest and heaviest woods	Decking and boardwalks; durable outdoors and insect resistant

Janka hardness of other species

Species	Janka (lbf)
Cumaru (Brazilian teak)	3,330
Brazilian cherry (jatoba)	2,350
Hickory, pecan	1,820
Black locust	1,700
American beech	1,300
Yellow birch	1,260
Red maple	950
Paper birch	910
African mahogany	830
Honduran mahogany	800
Sycamore	770
Basswood	410
Balsa	70

Properties

Physical

Density: generally higher than softwoods, but the ranges overlap; balsa is softer than most softwoods

Mechanical

Hardness: Janka values above run from 70 lbf (balsa) to 3,684 lbf (ipê) for the species listed; the full Janka table runs above 5,000 lbf

Durability

Decay: heartwood is more decay resistant than sapwood; teak and ipê are rated durable outdoors; black walnut is called one of the most durable United States hardwoods; white ash deteriorates quickly in soil contact

Uses in buildings

Building elements

Hardwood Flooring: solid and engineered flooring
Stile and Rail Wood Doors, Flush Wood Doors: stiles, rails, face veneers, and edge bands
Interior Millwork, Cabinetry and Casework: trim, paneling, and casework
Exterior Decking: dense tropical species such as ipe

Pros and cons

Pros

Wide hardness range, from 410 lbf (basswood) to over 3,000 lbf (cumaru, ipê)
Dense tropical species suit exterior decking
Grain and figure are valued in flooring and cabinetry

Cons

Solid hardwood joinery is costly
Teak and mahogany are scarce from over-exploitation
Mislabeled species and forged certificates in the ipê trade

Manufacturing and cost

Main manufacturers and suppliers

Weyerhaeuser

Trade associations: National Hardwood Lumber Association; American Hardwood Information Center.

Sources

Wikipedia: Hardwood, https://en.wikipedia.org/wiki/Hardwood
Wikipedia: Janka hardness test, https://en.wikipedia.org/wiki/Janka_hardness_test
Wikipedia: Oak, https://en.wikipedia.org/wiki/Oak
Wikipedia: Acer saccharum, https://en.wikipedia.org/wiki/Acer_saccharum
Wikipedia: Fraxinus americana, https://en.wikipedia.org/wiki/Fraxinus_americana
Wikipedia: Juglans nigra, https://en.wikipedia.org/wiki/Juglans_nigra
Wikipedia: Prunus serotina, https://en.wikipedia.org/wiki/Prunus_serotina
Wikipedia: Liriodendron tulipifera, https://en.wikipedia.org/wiki/Liriodendron_tulipifera
Wikipedia: Tectona grandis, https://en.wikipedia.org/wiki/Tectona_grandis
Wikipedia: Handroanthus, https://en.wikipedia.org/wiki/Handroanthus
Wikimedia Commons: Pine hardwood floor board from Long-Bell Lumber Company.jpg, photo by RichardTallent (CC BY-SA 3.0), https://commons.wikimedia.org/wiki/File:Pine_hardwood_floor_board_from_Long-Bell_Lumber_Company.jpg
ITTO: tropical log production, imports down in 2020, https://www.itto.int/news/2021/08/30/tropical_log_production_imports_down_in_2020_itto_releases_latest_review_of_world_timber_situation