treated wood

Toby Hemenway hemenway at jeffnet.org
Sun May 9 13:55:18 EDT 1999


Joann wrote:

>Does anyone have any thoughts or suggestions on substitutes for treated
>wood.

I'm glad you're designing an arbor that doesn't use  CCA
(copper/chromium/arsenic) treated wood; we can do without those in our food
and soil. The problem I assume you're hoping to avoid is wood rotting
because of ground contact. I can think of two strategies to deal with the
problem.

1. Use a rot-resistant substance: woods such as cedar, black locust,
redwood (preferably sustainably grown, salvaged, or used), cypress,
mulberry, osage orange, or Pacific yew (there's lots of this in the NW
because of the taxol industry). You could avoid wood altogether on the
ground-touching parts, and use metal, plastic, or concrete posts (if you
don't mind the embodied energy in concrete, Ken Kern's "Owner-Built
Homestead" gives directions for concrete posts; they will outlast
civilization but need months to cure). Traditionally, charring the end of a
non rot-resistant wood post has been used to make it last longer; soil bugs
won't eat charcoal. I've never tried it.

2. Keep the wood off the ground. Set wood posts on a rock foundation; the
rock beneath the post should slope or curve to keep water from pooling (the
wood will rot eventually but much slower than in the ground) or on metal
fence-post connectors set in concrete footings. If you do this, you'll need
to use ample diagonal bracing where the posts connect to the crossbars,
since the post-in-the-ground technique helps stiffen the arbor.

For a kiwi arbor, make it really strong: kiwi vines weight far more than
grapes; I've seen  them break down a convetional grape trellis

I hope this helps.

Toby Hemenway



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