If you're building outside next year, read this

As of December 31, 2003, lumber containing Chromated Cupric Arsenide will no longer be manufactured for residential use. (it will still be available for industrial use, and for permanent foundations.) This post is to describe the new wood treatments, and to give you a short list of dos and don'ts when working with it.

Understand first that CCA wood is still safe. It can be made even safer by coating it with a clear preservative--anything that's reasonably thick is fine. The gold standard is Sikkens Cetol; it also costs around $60 a gallon. An American-made product that works well is Flood CWF/UV. (Don't use Thompson's Water Seal for this; it doesn't work for this purpose.)

There are three treatment options that a lumber company can choose. The first is borate. When exposed to water, it leaches too fast to use, but it's good as the bottom plate in a wall, or some other built-in use. They also treat siding with it.

The other two options are both copper-based. The first is Alkaline Copper Quaternary, or ACQ. The other is Copper Azole, or CA. These are essentially interchangeable; your local lumberyard will probably have both products at various times.

ACQ is exceptionally safe: some shampoos list it as an ingredient. CA is probably about as gentle.

All the old-time handymen will remember the last time someone attempted to get the government to regulate a building product: we got the toilet that holds a cup and a half of water. This is different. ACQ and CA have been used in Europe for the last fifteen years. This stuff works. We know it works.

The biggest change in ACQ/CA lumber is the fasteners you use. There is enough copper in this wood to cause galvanic corrosion of aluminum and of unprotected steel. I don't mean it will get a little rust--I mean it will rot the heads off nails. It is, however, very safe to use stainless steel, copper and galvanized fasteners with ACQ/CA.

Some rules:

* Do not use aluminum flashing with ACQ/CA. Use copper, galvanized (if you can't get anything else) or EPDM flashing.
* Do not put aluminum plinths (little metal feet that go under porch columns and other such structures; their purpose is to raise the timber up above any water that gets on your porch) in contact with ACQ/CA lumber. Until we can get some brass or bronze plinths, your best bet would be to put a sheet of EPDM rubber between the aluminum plinth and the ACQ/CA lumber.
* Simpson also makes an aluminum post cap. Needless to say, don't get any of those either.
* If your project calls for metal ties such as joist hangers, use something equivalent to the Simpson ZMax series. (Example model number: a 2x6 joist hanger is LUS-26 if it's not what you want and LUS-26-Z if it's the right thing.) These hangers are triple-dipped in molten zinc, as are Simpson's special joist hanger nails.
* Only use hot-dipped galvanized nails with ACQ/CA. The days of grabbing any old nail and pounding it in are over.
* Deck screws: the best kind are polymer-coated. Phillips (the screw company, not the oil company) makes a screw called Deck-Mate in three polymer coatings: one for CCA, one for cedar and redwood, and one for ACQ/CA. There are other brands that do the same thing. As good but more expensive are stainless steel ones. Then there are hot-dipped galvanized screws. Don't put a drywall screw in this stuff because it will not survive. (I'm not sure what you do right now if you use composite decking like Trex, ChoiceDek or Fiberon; the special screw used with those deck boards is not yet ACQ/CA ready, although I predict that it will be very soon.)
* Do not, whatever you do, make an underwater structure from this wood! It leaches copper when you submerge it; copper is extremely toxic to aquatic life. CCA is much better for this and will remain available for this purpose.
* ACQ/CA wood carries no HAZMAT restrictions; CCA is listed as a hazardous material by OSHA. You can landfill ACQ/CA scraps (you can't landfill CCA scraps) and you can linehaul ACQ/CA without a HAZMAT permit. You still can't burn ACQ/CA. Burning CCA liberated chromium and arsenic; burning ACQ/CA liberates copper. Neither of them is any good for you when inhaled.

Reading the labels: There are four grades of ACQ/CA, due to the fact that the chemical is so expensive. The first of the four grades is Decking--all 5/4" boards are Decking grade, and probably all fencing too. Then we have Above Ground, which is all 2x stock--2x4s, 2x6s and so on. Ground Contact wood (which at this time seems to all be ACQ; my computer doesn't list any CA timbers) is 4x and 6x stock, and PFD, or Permanent Foundation, wood can be any dimension (although all PT plywood will be this grade) but very heavily treated because it's made to be buried. In the CCA days it would have been .40 lb/cu ft CCA retention for everything but Below Ground wood, which was .60 lb/cu ft, and fencing, which was .25 lb/cu ft.

That's what I know so far.

I forwarded that on to my husband, who is wanting to build a shop next spring. If I tell you how wonderful you are, will you check out my thread 'Need Advice from a Tool Guy' and if you can't answer, at least kick it? :)

You're WONDERFUL! :toast:

//nt//

Instead of mucking about with chemical impregnated wood, there is an alternative. Recycled plastic lumber for decking, structural recycled plastic like Polywood (a composite of recycled HDPE and polystyrene) for structural bits. www.polywood.com and US Plastic lumber make this stuff. Your deck and children's playgym will outlive you with this stuff.

Advantages: removes trash from waste stream, does not rot, stain, warp, decay, burn well, contribute to deforestation, or involve toxic chemicals. Disadvantages...well...not much. Doesn't quite look and feel like wood, but it's close. A little pricy, but that is easily made up by the complete lack of maintenance. At the end of its life it can easily be recycled again. Since the plastic is oil-derived and it's already out of the ground, you might as well turn those one-use grocery bags into something worthwhile and keep that carbon out of the atmosphere.

Composite plastic/wood like Trex and Weatherbest do not yet have evidence of long-term behavior and typically only carry 10-year warranties. All-plastic will last decades, easy.

Naturally rot-resistant wood like cedar is heavily clearcut in Canada and should be avoided. For the US there are locally grown woods, black locust and orange osage, that can be hard to find but will easily outlast cedar, even in the ground. Tropical woods like ipe should be avoided, again, due to massive rainforest deforestation related to its harvesting.

due to price sensitivity, and here you are talking about 100-percent-plastic alternative materials! And naturally-resistant woods!

I will agree that building out of synthetics or naturally-resistant woods is the way to go, if you can swing it. My customers, though, are of a different mindset: if I can build an 8x8 deck for $2500 out of synthetic, or an 20x24 deck out of PT pine for the same amount, give me the PT pine and a respirator for when I build the deck.

And that is the reality we all have to face: a big deck is better than a little one. You can do more with it. An 8x8 deck is basically a large porch; a 20x24 deck is large enough for parties and cookouts. (It's also bigger than most of the decks I sell--a real nice deck around here is 12x16.) A 16-foot stick of Fiberon composite decking costs $22.24. A 16-foot stick of Eon full-synthetic decking costs $36, but a 16-foot stick of PT pine runs about $8.

My favorite decking you'll laugh at: mahogany from a managed forest. Mahogany is naturally-rot-resistant (there is a reason mahoganies are used as floor underlayment), very easy to work, more durable than plastic decking and fairly close in price to the fully-synthetic decking. And people do use it as decking. I can get one-inch mahogany that's been wide-belt sanded for about six bucks a board foot, or $48 for a 16-foot stick. Put a coat of Sikkens Cetol 1 on it every spring, and it will outlast your house. But if I told my rich customers to put mahogany decking on the decks around their $350,000 houses, they'd call the store manager and request I be drug tested. A mahogany deck? Who ever heard of such a thing?

As a liberal, I can dream of the day when wood isn't used for such mundane purposes as building decks. As a lumberman, I have to deal with the reality that decks are going to be made of wood.