Reusing Lumber -- Weather Effect?

[grwold]

I recently took out an old, sagging, cedar picket fence, and now I've started planing down some of the pickets to re-use.

What I'm finding is that as I plane off the old, lichen-infested surface, at first I get this rather nasty, gray-green dust.  Then I start getting some threads mixed in, from the harder parts of the rings.  Eventually the shavings become web-like, and after getting deep enough, they begin to look like real wood (and I finally get that cedar aroma, too).

So, what has the weather done to the surface of the fencing, over the years?  It seems as if the wood cells(?) have been hollowed out over the years.  Is this a common effect as wood ages, or only because the fence was fully exposed to the weather?

[hbmcc]

I recently took out an old, sagging, cedar picket fence, and now I've started planing down some of the pickets to re-use.

What I'm finding is that as I plane off the old, lichen-infested surface, at first I get this rather nasty, gray-green dust.  Then I start getting some threads mixed in, from the harder parts of the rings.  Eventually the shavings become web-like, and after getting deep enough, they begin to look like real wood (and I finally get that cedar aroma, too).

So, what has the weather done to the surface of the fencing, over the years?  It seems as if the wood cells(?) have been hollowed out over the years.  Is this a common effect as wood ages, or only because the fence was fully exposed to the weather?

Wood deterioration includes weathering, attack by mold and fungus, which are the common early vehicles of decomposition. The lichen is the next level of the decomposition cycle. If you grow tomatoes over a wood deck, individual plants will accelerate the process of reduction. Insects jump in when the natural toxins leach away.

Solar/UV degradation of unprotected wood (silvering) is the first point of degradation. I recall reading that the sun will tear down surface structure at about 1/16th inch a year. At some depth UV will be blocked by the "dead" wood layers. However, wear by rain, by animals (birds and squirrels) and paper wasps will continue the weathering process. 

You can get a better explanation by searching for and reading real science from people like Bruce Hoadley, and USDA, if stupid traters haven't destroyed it.... https://www.fpl.fs.fed.us/documnts/fplgt...gtr190.pdf  My science is from experience and about 40 years in the business. You can plan your own salvage and rebuild, but I'll add my own summary:

In about 2010 I decided to dismantle, pressure wash and salvage as much of my backyard fence as I possibly could when rebuilding it. At the time it was about 25 years old. The western red cedar pickets were cut back to 5-feet length, clear of decay at each end--soil and exposure decay. The rails, Wolmanized (P. treated), were trimmed about as much to remove angle cuts for slope and toenailing damage. All I bought were nails and new pressure treated posts. I went from 8-foot spacing to 7-foot and only removed one concrete footing. 

It was a lot of work, rewarding, but only gained ten to 15 years on wood that was hundreds of years old when cut. Western US forests have a paucity of  old growth wood which is the only wood that is durable. The current treating standards and wood used locally is so poor I got about 7 years from the posts before they rotted and fell apart.

YMMV