Raised Planter Box - Treated Wood
May 9, 2022 10:41 AM Subscribe
I made a raised planter box from reclaimed pressure-treated wood and didn't consider its possible issues - e.g. toxicity - until it was finished.
Can I make it safe to use for growing vegetables and herbs?
It's about 2'x4' square and about 16" deep. The wood is from my kids' backyard fort, which I built around 2008/9. I washed it with a bleach solution for mildew and rinsed it thoroughly, then sanded it. (I was outside, wearing a mask.) It has drainage holes and the bottom of the box is about 2' above ground.
Options:
1. Minimal: Line it with permeable landscaping fabric, add a drainage layer of rock, fill it with soil.
2. Medium: Line it with an impermeable layer (food-safe plastic, galvanized metal), drill drainage holes through that, then rock, then soil. Maybe corrugated fiberglass cut to size?
3. Intensive: Seal the wood with some kind of safe finish, then permeable landscape fabric, etc.
4. Do Nothing: There's nothing to worry about here.
5. Flowers only: This cannot be made safe for things you eat.
6. Something I haven't thought of yet.
It's about 2'x4' square and about 16" deep. The wood is from my kids' backyard fort, which I built around 2008/9. I washed it with a bleach solution for mildew and rinsed it thoroughly, then sanded it. (I was outside, wearing a mask.) It has drainage holes and the bottom of the box is about 2' above ground.
Options:
1. Minimal: Line it with permeable landscaping fabric, add a drainage layer of rock, fill it with soil.
2. Medium: Line it with an impermeable layer (food-safe plastic, galvanized metal), drill drainage holes through that, then rock, then soil. Maybe corrugated fiberglass cut to size?
3. Intensive: Seal the wood with some kind of safe finish, then permeable landscape fabric, etc.
4. Do Nothing: There's nothing to worry about here.
5. Flowers only: This cannot be made safe for things you eat.
6. Something I haven't thought of yet.
(If it makes you feel better, the really nasty arsenic-containing PT stuff hasn’t been sold in a long time.)
posted by supercres at 10:58 AM on May 9, 2022 [1 favorite]
posted by supercres at 10:58 AM on May 9, 2022 [1 favorite]
According to the US EPA:
Effective December 31, 2003, chromated arsenical manufacturers voluntarily canceled virtually all residential uses of CCA, and wood products treated with CCA are no longer used in most residential settings, including decks and children’s playsets.
The newer pressure treated stuff is considered safe for use in crop containers; but if (like me) you like to hedge against the possibility that future studies will reveal issues that we haven't yet figured out, an impermeable liner should give you confidence that it will be safe to use for things you intend to eat.
posted by fikri at 11:13 AM on May 9, 2022 [2 favorites]
Effective December 31, 2003, chromated arsenical manufacturers voluntarily canceled virtually all residential uses of CCA, and wood products treated with CCA are no longer used in most residential settings, including decks and children’s playsets.
The newer pressure treated stuff is considered safe for use in crop containers; but if (like me) you like to hedge against the possibility that future studies will reveal issues that we haven't yet figured out, an impermeable liner should give you confidence that it will be safe to use for things you intend to eat.
posted by fikri at 11:13 AM on May 9, 2022 [2 favorites]
I think the stuff using pentachlorophenol is even worse than CCA treated wood.
Pentachlorophenol is banned from all uses in the EU, and was scheduled to be banned in the US by Carter's EPA, but the Reagan Administration overruled that.
posted by jamjam at 11:41 AM on May 9, 2022 [2 favorites]
Pentachlorophenol is banned from all uses in the EU, and was scheduled to be banned in the US by Carter's EPA, but the Reagan Administration overruled that.
posted by jamjam at 11:41 AM on May 9, 2022 [2 favorites]
Response by poster: I don't mean to threadsit, but I should have mentioned that the pressure-treated lumber was rated for residential use - that is, for decking (i.e. 5/4 x 6" planking), walkways, etc. Got it from Lowe's, I believe.
posted by Caxton1476 at 11:53 AM on May 9, 2022
posted by Caxton1476 at 11:53 AM on May 9, 2022
We have a number of raised garden beds like these, where the inside of the bed is primarily exposed to the corrugated, galvanized metal. though the seams are exposed to the pressure treated wood.
I test our soil every year; nothing odd has come up, other than normal deficiencies, from growing things in soil year after year. Risk is already pretty low, this bumps it firmly into 'not zero, but acceptable' territory for me and my family.
I would line them with galvanized metal, and call it a day.
posted by furnace.heart at 2:24 PM on May 9, 2022
I test our soil every year; nothing odd has come up, other than normal deficiencies, from growing things in soil year after year. Risk is already pretty low, this bumps it firmly into 'not zero, but acceptable' territory for me and my family.
I would line them with galvanized metal, and call it a day.
posted by furnace.heart at 2:24 PM on May 9, 2022
I think your option #2 is the best choice. An impermeable plastic liner should make things safe regardless of whether the PT lumber leaches anything toxic over time.
posted by biogeo at 4:40 PM on May 9, 2022
posted by biogeo at 4:40 PM on May 9, 2022
(Current structural treated wood is copper compounds (non-arsenical league); pentachlorophenol has been only in specialized applications like utility poles for a while now.)
posted by away for regrooving at 8:16 PM on May 10, 2022
posted by away for regrooving at 8:16 PM on May 10, 2022
Response by poster: Thank you, everyone, for the guidance!
I think I'm going to line the bottom with some plastic gardening flats (the kind a garden center uses to display/sell seedlings), then, if I can find some, line the sides with corrugated roof material. That'll give my family some extra piece of mind.
Cheers!
posted by Caxton1476 at 9:58 AM on May 11, 2022
I think I'm going to line the bottom with some plastic gardening flats (the kind a garden center uses to display/sell seedlings), then, if I can find some, line the sides with corrugated roof material. That'll give my family some extra piece of mind.
Cheers!
posted by Caxton1476 at 9:58 AM on May 11, 2022
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posted by supercres at 10:56 AM on May 9, 2022