Janka Hardness
A standardized test measuring the force required to embed a 0.444-inch steel ball halfway into wood — the primary tool for comparing wood species hardness and wear resistance.
In Detail
The Janka hardness test (ASTM D1037) measures Wood resistance to denting and wear by recording the force in pounds-force (lbf) needed to push a 0.444-inch (11.28 mm) steel ball to half its diameter into the wood surface. Higher numbers mean harder wood and better resistance to surface damage.
Common reference points: Western Red Cedar = 350 lbf (soft — decks easily and needs careful fastening). Southern Yellow Pine = 1,225 lbf (moderate — standard framing). White Oak = 1,360 lbf. Ipe = 3,510 lbf (extremely hard — among the top commercial species). Brazilian hardwoods used for decking typically range from 2,000–5,600 lbf.
For decking, Janka hardness is one factor in durability — but resistance to rot, UV, and moisture matters as much or more outdoors. A low Janka species like cedar can outperform a hard species in outdoor longevity if the harder species lacks natural durability.
Related Materials
Ipe Decking
Ipe (Handroanthus spp., formerly Tabebuia) is an extremely dense Brazilian hardwood prized for exceptional durability, fire resistance, and a rich dark-brown appearance. Often called "ironwood," it's the premium choice for high-end residential and commercial decks.
Cedar Decking
Western Red Cedar (Thuja plicata) is a premium natural decking choice valued for its natural decay resistance, dimensional stability, and warm appearance. The go-to natural wood deck board for contractors and homeowners seeking a traditional aesthetic.