Depends. The range in specific gravity (density) for Doug fir in a large sampling in the West was .33-.59. 95% of all samples were between .36-.54 with the mean being .45. This sampling was done in the late 60's and early 70's and included old growth trees.

Studies have shown that Doug fir from low elevations can have wood 10% denser than from higher elevations in the same region. In addition, Doug fir from west of the Cascades and from low elevations in the Inland Empire can be up to 20% harder than Doug fir sourced from the Rocky Mtn. region (Colorado/New Mexico).

Younger trees do have lower average specific gravity (density), but this is mainly due to the effect of juvenile wood in the inner core of the tree (10-20 years). The center of the tree is not typically used for making select or clear flooring because of the large number of knots. Additionally, studies with Doug fir have shown that once the tree reaches about 75 years, the specific gravity levels off around .50 and only trees from low elevations in the Cascades showed an additional 10-15% density increase into the "old growth" years.

Wood doesn't harden with age. Once it is kiln dried to 6-10% MC (and the pitch is set for Doug fir) it has a given specific gravity. The only way that would change is to add something to it like water or chemicals.

High ring count (in a given piece of wood) could be caused by a young tree being suppressed or by an older tree with slow growth due to old age. Generally, once a tree reaches 50-75 years in age, the specific gravity of the wood from that point out does not change much.

Janka hardness is directly related to wood density or specific gravity.

Lots of grain (like in rift-sawn, tight ringed Doug fir) tends to mask or hide dents. A satin or matte finish also tends to hide surface scratches. Doug fir is fine for flooring, just accept that it will dent more.

Very interesting! Thanks for the info. The fir we're considering is coastal Douglas fir from Vancouver Island in British Columbia. Will look for examples of rift-sawn and matte finish. Makes sense that the grain would hide the dents.

I installed new growth Doug fir in my house in San Francisco. Although the color and grain were simply gorgeous, it was incredibly soft. It dented if you looked at it wrong. If I'd had it to do over again, I would have chosen something harder.

"Wood doesn't harden with age. Once it is kiln dried to 6-10% MC (and the pitch is set for Doug fir) it has a given specific gravity." Tell that to the old timers in B.C. I myself have tried to plane 75 year old DF with virtually ZERO success. 3" common nails can not be shot into it and get penetration through into next board. Nails are drilled prior to using... That is the established method for re - employing salvaged DF. Someone needs to look at that if that so called wisdom is tested!

" Someone needs to look at that if that so called wisdom is tested! "

Yes, someone needs to look into why someone would pull up a 16 year old post for that tidbit of info.