Pressure Treated Wood- How Safe?-How can it be finished?


Old 05-18-01, 06:25 AM
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I am a little concerned about using PT wood as my deck suface for a few reasons. First is that there will be a lot of children using this deck and of course I am concerned about any transfer of chemicals from the wood to the children and/or the pool water.

Next, how is PT wood finished? Will it take a stain? I know that it is very dark when its new so do I wait till it dries out before staining? I have an existing Cedar deck near by and I realize that they are 2 different woods but I would like them to appear somewhat the same. Cedar deck will be stained a dark brown.

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Old 05-18-01, 02:57 PM
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Pressure-treated wood is usually treated with CCA (chromated copper arsenate) which gives it the green color. The wood is put into a sealed tube, a vacuum is created in the tube and the white cells of the wood, and then the tube is flooded with the CCA, and pressurized into the wood.
CCA contains arsenic, among other things, which protects the white wood cells from insects and rot. The CCA does not penetrate the naturally rot/insect-resistant red wood cells of the pine.
CCA can be harmful IF you inhale the smoke if burning it (the only really dangerous thing), or a LOT of sawdust, if sawing it. And, of course, anything with a protective chemical in it should not be chewed or eaten by children or pets. They would probably have to eat a whole board to harm them in any way, if even then.
Otherwise, p-t wood is perfectly safe for normal use by your family, such as decks, etc. That's what it's made for. Millions of boardfeet have been safely used for family decks.
The CCA, once it's dried (it crystalizes in the wood cells), won't "transfer" even if re-wet, unless it is consumed in a modified, concentrated quantity, such as in heavy smoke.
It usually is air-dried in the treatment plant yard, but you should let it "weather" and dry out for a few months in place if it is relatively new, before staining it. You can stain or paint it just like any untreated wood then.
With a little experimentation, you should be able to match stain the red wood and p-t wood pretty closely.
Good Luck and enjoy your deck!

Old 05-23-01, 07:45 AM
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OldGuy is exactly right. You have to let the PT lumber weather before staining it. I know that the Thompson's stain that I used to sell told right on the can how long to weather the lumber before staining. It was either 30 or 60 days.


Old 05-23-01, 01:26 PM
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The US Forest Service has been using pressure treated picnic tables for ages.............and they still do.
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