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duajones April 2, 2007 10:43 AM

Treated lumber?
Just wondering how many of you use treated lumber for your raised beds. I removed my dilapidated greenhouse and am going to add another raised bed. I used treated lumber on my first bed, just curious as to what you guys use.


feldon30 April 2, 2007 10:51 AM

This is one of those perennial topics that can be a bit controversial.

Pressure treated wood is treated with an arsenic-like compound.

The questions to consider:
* How much leeches into the ground?
* How much makes its way into your veggies?
* How much longer does it last than regular lumber?

Some of my garden beds are pressure treated, some aren't. It came down to budget for me.

I suppose weed barrier could be used to try to keep some of the chemical seepage out of the soil. Some tests have been done (no, I don't have links), showing that the amount of hazardous chemical that leeches into the vegetables is very low, but I don't blame people for not wanting to take that risk.

Untreated lumber may need to be replaced as often as every 2-3 years.

dcarch April 2, 2007 10:59 AM

FYI: Googled this:
" Nearly 40 million lb. of arsenic is used in this country every year, and most of it goes into the pressure-treated wood that we use to build decks and playgrounds. But that all changes Jan. 1, 2004. The Environmental Protection Agency (EPA) is banning chromated copper arsenate (CCA) as a preservative for wood intended for residential use (except for the lumber that is used in permanent wood foundations). CCA-treated lumber will still be available for industrial and agricultural use, however.
By the way, there's no need to panic about existing CCA-treated structures. The EPA says that they're fine. But if you're nervous about the chances of leaching chromium and arsenic, you can make your deck or swing set safer by coating it with an oil-based penetrating stain every couple of years.
Taking CCA's place as a preservative are two waterborne compounds: alkaline copper quat (ACQ types B and D) and copper azole (CBA-A, CA-B). Sold under the trade names Preserve, NatureWood, and Natural Select, they have been used around the world for up to 15 years. These EPA-approved low-toxicity pesticides resist bugs, mold, and rot as effectively as CCA. (See How much safer? for more on quat and azoles.)"


Tomstrees April 2, 2007 11:06 AM

Glad you guys posted this as I was going to use the wooden "kiddie" playground set when I take it down this spring for raised beds ,,,
I wonder if its old enough for it not ot matter ?

I'm strickly organic so ... prob. wouldnt want to take that chance ~


duajones April 2, 2007 11:14 AM

Acq is what everyone carries locally.

dcarch April 2, 2007 11:24 AM


Originally Posted by Tomstrees (Post 52894)
-----I was going to use the wooden "kiddie" playground set when I take it down this spring -----------

You may need the Kiddie playground set sooner then you think.:arrow: :lol:


keithaxis April 2, 2007 11:32 AM

I buy what they call green wood. It is 4" by 6" by 8' and it seems to last very well. I built more first 9 raised beds out of it 4 years ago and it is still looking real good with no rot at least on outside...only thing leaching from the "green wood' is sticky sap...
Those boards make some nice hefty, sturdy raised beds..I have...$12 for each board so it does add up but I love em...


feldon30 April 2, 2007 11:55 AM

4" x 6" wow that's thick.

feldon30 April 2, 2007 05:41 PM

Think I'll run right out and buy some YellaWood (What they are calling it here) with confidence. ;)

dice April 2, 2007 07:09 PM

Why not use broken up concrete? Anytime that
I browse Craig's List, I see it available for free.
One can mortar manageably sized chunks of it
together with type-S mortar ($5 for a good-sized
bag at HD). It requires some exertion and
muscle to hand-mix the mortar in a bucket,
but the wall will not rot, is not toxic (lime,
gypsum, and various kinds of sand and gravel),
and one can make the sides as high as one desires.

One can easily make it higher in successive
years after adding more compost, manure, topsoil
or whatever to a raised bed: simply mortar another
layer of concrete chunks on top of the existing walls.

(People who habitually overbuild will want to
pound 2-3' pieces of rebar into the soil every
4-6' of wall, with 4-6" left sticking up into the
mortar between chunks of concrete in the bottom

Wood is light and easy to machine and looks
nice in a yard, but it does rot, especially in
contact with soil. Concrete is heavy and requires
muscle to build with, but it does not need to be
treated with anything to avoid rot. One can
make it a little easier to work with by ignoring
"must take all or nothing" listings and only
selecting chunks that one could easily carry from
the pile of debris to one's vehicle. (Caveat: using
small pieces requires more mortar.)

landarc April 2, 2007 08:06 PM

The caveat with pressure treated wood without the old treatments is that it does seem to be more susceptible to decay. In fact, in our experience in California, pressure treated wood is rapidly losing favor to other materials as it is not a long term solution where soil contact is considered. The process, more so thatn the chemicals seem to be at fault, with deoth of chemical treatment being the biggest issue. In fact, most of the manufacturers no longer warranty the produict for soil contact at all. The key is keeping moisture from building up in contact with the wood. One of the ways we see this being achieved, is by backing the walls with drain rock wrapped in filter fabric to a width of at least 6" and leaving a gap of 1/2" above grade to allow drainage. Also, many advocate that all cut ends be treated with preservative prior to assembly of structures.

BTW, as recently as a year ago, I saw some old stock with CCA tags, there is still some old illegal stock out there. As well as Wolmanized lumber.

Sherry_AK April 2, 2007 10:19 PM

Most of our beds are pressure treated wood. I've read that the arsenic leaches only a very short horizontal distance. In the veggie beds we dug out a few inches of soil, added a non-pressure-treated liner, and filled it back up. Probably not necessary, but I feel better.

where_with_all April 3, 2007 09:22 AM

I have a pressure treated fence and have often wondered about it, but I have been reassured multiple times that its ok.

Tomstrees April 3, 2007 09:24 AM

Dcarch ~

HA HA !!! LOL ~ wait a minute..:shock: might be onto something here! :mrgreen:

~ Tom

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