We divide the many species of oak (genus name is Quercus) into two basic groups: Red oak and white oak. Within each of these groups are about 20 species that are commercially used for lumber. However, almost all lumber is sold as either red or white and the species separations are not made.
In the woods, if the leaves on the tree are rounded at the ends, it is in the white oak group. Pointed ends mean red oak. Sweet acorns, white oak; bitter, red oak.
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For lumber, some general differences are:
- - White oak tends to be slightly heavier than red oak
- - White oak tends to be slightly stronger, harder and stiffer than red oak, but not always
- - White oak, when freshly sawn is about 65 percent MC; red oak is 80 percent MC
- - Some of the red oak species have a reddish color (especially cherry bark oak), but some do not; some white oaks are darker and some are redder than red oaks (but color is not a good separator between white and red)
- - Most white oaks have the large pores in the wood plugged (and are used for whiskey and white barrels), but red oak is not plugged (technical term for being plugged is occluded)
- - White oak dries more slowly than red due to occlusions
- - When finishing, red oak is more porous than white due to occlusions
- - Any gluing differences between the two groups are small and are overshadowed by other factors, such as moisture content
- - Any mating differences between the two groups are small and are overshadowed by other factors such as grain angle and moisture
- - The ray cells on white oak are longer (over 1-1/2 inches long often in white vs. ½ inch in red) and wider; this difference creates an overall appearance difference and this difference is how experienced people can separate red and white instantly
- - The ray pattern contrast even in flatsawn grain makes white oak look “heavier” which is an often an undesired appearance difference to many North American consumers (except in Mission Style furniture); in contrast, European and Asian consumers like the heaviness of white oak
- - On a quartersawn surface especially, white oak has more dramatic ray fleck patterns than red oak
- - On the average, flatsawn white oak shrinks and swells with moisture content changes slightly more than red
- - White oak has natural decay and insect resistance; red oak has little resistance
Overall, for most properties there is more variation within each group than between the two groups. For this reason, the geographic source of lumber is often very important to maintain consistency.
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