Douglas fir is a single species of tree that grows primarily in America's Pacific Northwest. It is a soft wood, in the same category as pine, spruce or cedar, used primarily for structural framing. Oak is a generic name for a number of individual hardwood species, used for flooring, siding, trim and furniture and other applications from railroad ties to crates to fence posts.

Forest in the Fog
credit: randimal/iStock/Getty Images
A path through several Douglas fir trees.

Douglas Fir Forests Most Productive

Douglas fir is a distinct species first discovered by a Scottish naturalist on Vancouver Island in 1791 and named for David Douglas, a Scottish botanist who identified it in 1826. Douglas fir timberlands are the most productive softwood forests in America, with Oregon the leading producer. The region has had systematic replanting since 1912 to ensure a continuing supply.

Fir is Framing Lumber

Douglas fir is a dominant framing lumber, with a superior strength-to-weight ratio, great nail-holding ability and elasticity for resistance to such natural forces as wind, earthquakes and storms. Fir from trees from the Cascade Crest to the Pacific is identified as DF. Lumber from the eastern slope is graded DF-L because the species intermixes with Western Larch, which has nearly identical properties. Fir from other mountain states and Canada is marked with S for south or N for north.

Oaks Dominated Eastern Hardwood Forests

Oaks were the dominant trees in the forests referred to as eastern hardwoods when settlers first arrived in America. There are many varieties but white and red are the dominant types in construction and other applications. White oak, which varies in color from light tan to pale yellowish-brown, is the most common hardwood flooring and also is frequently used in dining room tables and other furniture. Red oak is a deeper reddish brown, also used in flooring and furniture but also for many non-building purposes.

Oak is Tough, Rot-Resistant

Oak is tough, fine-grained, resistant to rot and extremely strong and durable. Oaks have the broadest distribution across the United States and southern Canada. There are many variations within the generic white oak and red oak classifications, with many different species producing similar colors of wood. There also are geographic differences, with northern and southern trees differing in density and texture.

Which is Harder?

Anyone who has ever driven a nail into a Douglas fir stud or an oak beam or tried to saw lumber with a hand saw will know which wood is harder. Douglas fir nails easily and holds securely because of its high specific gravity. Oak generally must be predrilled for nailing although it holds nails and screws tightly. All oaks tend to dull sharp cutting edges because they are so hard. The Janka Hardness Scale, a standard measurement of force to drive an object into wood, uses red oak as a benchmark, at 1290. White oak rates 1360, harder than red oak. Douglas fir rates from 510 to 710, depending on its origin, with Pacific Northwest the hardest.