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Earlier today, I posted a question about building a small table with pressure-treated wood. A few people chewed me out for using PT wood indoors, so I deleted it.

So just now I called a lumber store for other options to PT wood, and he said that the next option (mahogany or cedar) were 5x the price of PT wood and out of my budget. But he said that if I followed the following steps, I could use pressure-treated lumber for my indoor table:

  • Wash the lumber with a hose and use clorox. Let dry.
  • Sand the wood.
  • Apply a layer of polyurethane.

Does this make sense? He said that all the PT chemicals would be sealed due to the polyurethane.

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    The current pressure treated wood in the US is much less toxic than the older versions. Having said that why are you using treated wood? non treated wood is less expensive. We used a picnic table made with the older treated lumber for years other than the tail we have had no side effects (tail is a joke). A strong detergent would be a better choice than bleach for cleaning the wood, PT wood is often very wet to start drying might take a long time. I am going to say I would not use it, but it is YOUR choice. – Monte Glover Dec 18 '19 at 2:33
  • I chose pressure treated wood because of termites. I guess I can ask in SE what I can use to make non-treated wood termite-resistant. – rbhat Dec 18 '19 at 3:02
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    What is the commercial furniture in your home made of? What I'm getting at is if you have a genuine problem with termites indoors you have far more to worry about than just this one table. – Graphus Dec 18 '19 at 7:53
  • I don't have a termite problem. Besides, this isn't really the point of the question. – rbhat Dec 18 '19 at 13:25
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    This entire comment thread is one of those where you want to exclaim "but that just raises more questions!" But, in general, this feels like an "X-Y question". You want advice on using PT lumber indoors, even though this is not recommended. And you got terrible advice on how to do so. The appropriate response is "why do you need to use this material at all?" Maybe take a step back and tell us how you got to considering PT lumber in the first place? – jdv Dec 18 '19 at 22:19
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I'm going to answer this question as if the primary question is intended: "is this a good way to treat pressure-treated lumber for indoor use" in case anyone else stumbles across this Q&A.

The answer is no.

  • Washing the lumber with water and bleach isn't going to do anything. PT lumber has been soaked or sprayed with a mixture of chemicals and then subjected to hours or days inside a sealed, pressurized tank so that these chemicals are pushed deeper into the lumber. These chemicals are intended not to wash off in water so washing the surface of the wood doesn't remove them. Using water with or without bleach will not remove these chemicals (to any significant degree) or otherwise make them inert or immediately safe, mostly because any surface treatment will never even touch the chemicals below the surface.

  • Pressure treated lumber has a much larger moisture content. It is heavy and wet and unsuitable for extended indoor use.

  • Sanding wood almost always makes dust that is dangerous to breathe, but in this case you are making dust laden with anti-fungals and so on, and (as stated in the first bullet point) the chemicals are there even if you wash the surface of the lumber. Sanding just makes it nicely available to living creatures who are exposed to that dust.

  • Polyurethane does not seal in a manner that would keep this lumber from off-gassing for most of its life. Maybe epoxy style finishes, applied thickly so that the wood was literally surrounded in plastic might work. Well, for some definitions of the word "work".

Pressure-treated lumber is for use outside. Modern PT lumber is reasonably safe if exposure is kept to a reasonable level. But working with the lumber requires being strict with your cleanup and dust management. Letting PT lumber off-gas in your house is not "reasonable" exposure, no matter how modern it is. Even with modern PT lumber no one would ever recommend indoor use, period.

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  • "Even with modern PT lumber no one would ever recommend indoor use, period." except for sill plates :) – UnhandledExcepSean Dec 20 '19 at 15:57
  • @UnhandledExcepSean heh, sure. Once you bury it under insulation, trim, caulk, primer and two coats of paint, I'd consider that outside. At that point it's just a surface to draw a bead of acoustic sealant on and staple 5mil plastic to! (Though, even in Canada we mostly use regular lumber for sill plates, just putting some of that 4inch pink closed-cell foam stuff between it and the concrete.) – jdv Dec 20 '19 at 16:23
  • Good answer. To add, the majority of lumberyard PT is extremely wet (~20% emc), so that would further disqualify it for furniture use. – Aloysius Defenestrate Dec 30 '19 at 0:40
  • @AloysiusDefenestrate good point. – jdv Dec 31 '19 at 14:18

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