Last time, when we started working on putting up a clothesline, there was a great disturbance in the force. Possibly up to a dozen people recoiled with a gasp of horror at the idea that I was using pressure-treated lumber. The very idea that I would be using such stuff got my name on the protest banners with Deepwater Horizon, nuclear weapons, and…apparently I use it to club baby seals? What’s the big deal? Well, this is an issue that has been cropping up since pressure-treated lumber started becoming widely available. I figured it might be prudent to address it here.
In the beginning there was wood. And it was good. But behold the fungus and termite doth corrupt it, and it was not good. And the habitations of men were thus vexed. But man reasoned within himself and did force noxious chemicals into wood, and the fungus and termite were repulsed, and the habitations of men were spared. And the peasants rejoiced.
The problem was with those noxious chemicals. We’ve been slathering stuff on wood to keep out the rot and bugs since roughly the Neolithic. Thus did we paint houses and coat utility poles in creosote. But this was something different. Instead of a thick, gloppy coating, we instead figured out that we could inject chemicals under high pressure into timbers and infuse them with
hints of acai and lavender anti-fungal chemicals. The chemical blend that ended up being chosen was CCA, or Chromated Copper Arsenate.
Yup, you read that last word right. Basically, treated lumber was impregnated with arsenic. So there were a lot of problems that emerged like the fact that contractors started getting sick from inhaling the sawdust and absorbing through the skin while working with it. The arsenic would also leach out into the soil and water (mostly a problem for docks and such). Admittedly, it wasn’t a lot, but it was some. And this worried people, particularly those who had made garden beds using this CCA-treated lumber.
Well, that’s the old news. In 2004, CCA got the kibosh from the EPA. But by now treated lumber was pretty well established in the building trades. For instance, if you have a deck, it’s because of treated lumber. Before then, it was a patio or nothing. The bridges on the bikeways here are mostly made from treated lumber. The idea wouldn’t have existed without treated lumber.
Enter ACQ, which is the treatment that gets used now, by and large. That stands for Alkaline Copper Quaternary. It’s still got copper in it (thus the greenish tinge), but uses an ammonium compound instead of arsenic. It’s pretty benign, as the literature has pointed out. If anything, it will help alleviate copper deficiencies in the soil, and so far as I’ve found, it isn’t mobile like nitrogen, so it doesn’t end up dumping out into the Gulf or Lake Erie.
So here are your options if you want to build outdoors, as of right now:
- Build it from regular old white pine and paint it a lot (and don’t put it on/in the soil)
- Use one of the tannin-rich native hardwoods like black locust or osage orange
- Use a tropical hardwood (teak, jatoba, ipe, etc.)
- Use a redwood, cypress, or cedar
- Use pressure-treated pine
I suppose you could add “pour concrete ad nauseam”, but it seems a bit superfluous. Regular pine just won’t cut it for this. If you can find black locust, good on you. That would be my preference, if I could afford it. In that same vein, tropical hardwoods and redwood are right out, though I hear that it’s quite the selling point for people with more money than they know what to do with. If you have this problem, send me some of that money because I’m sure I can find a use for it.
So we’re left with PT timber. Since the change to the ACQ method, I don’t really worry too much about it. It’s not like I make heaps of dust from the stuff, so exposure isn’t a problem. I do pick up my waste and bin it rather than compost it, but that’s not really a bit deal, and done more out of an abundance of caution than anything. Will I use it in the garden? Yup, sure will. The possibility of it being noticeable (let alone harmful to plants, let alone harmful to me) are down there with “lightning striking during shark attack” and “Chixclub crater”. Instead I’ll worry about much more likely things, like ending up as the hood ornament on a Kia. Or bird flu. Or the Yellowstone supercaldera opening up…
So go ahead and use PT timber. It’s not evil or anything. If you can afford something different, then by all means do so, but do it because you want something more beautiful. Don’t think you have to buy special cedar boards because PT timber will turn your backyard into a Superfund site, because they won’t.