I've been debating this same issue for a while my self. First option is regular 2x lumber should be good for 5- 6 years or more. Option #2 find a local lumber mill and buy some rough cut lumber. Personally I'd stay away from PT lumber or RR ties.
What wood to use for building a raised outdoor container bed - Page 2
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My wife wants to make a raised garden and reading this thread gave my an idea. I have access to bridge planks from torn down old wooden bridges that have been replaced by cement bridges and/or culverts. I think bridge planks would work excellent and last many years if you have access to some.
HARMELESS ? Take your shirt off and cut some .You will fell like fiberglass got in you . If you must use wood ceder or cypress . I like useing big plastic totes .Get clear ones to start from seed.Lid makes green house till plants get to big.
The old stuff was like that, but not the new stuff.
I built 4 huge decks with the new weakly "pressure treated" lumber. All were built in very high Summer heat. All were built without wearing a shirt, because I hate wearing shirts. No feeling other than the sweat running down, making the upper few inches of my jeans soaking wet, under my belt.
Boric acid, oxides and salts (borates) are effective wood preservatives and are supplied under numerous brand names throughout the world. Borate treated wood is of low toxicity to humans, and does not contain copper or other heavy metals. However, unlike most other preservatives, borate compounds do not become fixed in the wood and can readily be leached out. Therefore they should not be used where they will be exposed to rain, water or ground contact. Borate preservatives
. However, treated wood may present certain hazards in some circumstances such as during combustion or where loose wood dust particles or other fine toxic residues are generated or where treated wood comes into direct contact with food and agricultureAlkaline copper quaternary (ACQ) is a preservative made of copper, a fungicide, and a quaternary ammonium compound (quat), an insecticide which also augments the fungicidal treatment is a wood preservative that has come into wide use in the USA
Since it contains high levels of copper, ACQ-treated timber is five times more corrosive to common steelOther copper compounds
These include copper HDO (CuHDO), copper chromate, copper citrate, acid copper chromate, and ammoniacal copper zinc arsenatemicronized preservatives use nano particles of copper oxide, for which there are alleged safety concerns
Boric acid is roach poison alklines will eat your skin ammonia is poison cromate is a heavy metal causes brain dammage zinc can be poisonin small quanitys cream for dentures
You should NEVER use bleaches, deck cleaners or brighteners on old CCA-treated wood because they oxidize the chromium-3 that's already in CCA-treated lumber, turning it into the highly carcinogenic chromium-6.
Besides sealing your existing CCA-treated structures, you can replace the boards that get the most skin contact with alternatives to CCA-treated lumber. My favourite is Western red cedar, but it's expensive (i.e. approximately 20 dollars for an eight-foot long 4" x 4" post).
Or you can try replacing your CCA-treated decking with some of the new plastic composite lumber.
Or you can try the new pressure-treated lumber. The two most widely available preservatives that replace CCA are alkaline copper quaternary (ACQ) and copper azole (CA). They're very low in toxicity. But here's the deal; lumber treated with ACQ or CA has a much higher concentration of copper (from 18% to 96%) so it's more expensive than the old stuff. That's not all.
The high copper content means that any other metal (like nails, screws, bolts, or flashing) that comes in contact with the pressure-treated lumber sets up a mild electrical charge with the copper, making traditional steel fasteners and aluminium flashing corrode like crazy (up to five times faster than they'd corrode in the old CCA-treated lumber).
This risk of corrosion presents the possibility of structures becoming unstable or even collapsing because of incorrect fastener usage.
We made a nice raised garden out of landscape lumber. You can stack it as high as you want and nail it together with spikes. If your really concerned about chemicals leaching out you could coat the boards with deck sealer. Here's a photo of the garden.
Never had a problem with leaching. The new treated wood is much less toxic than the old stuff. I had the same thing when we lived in Ft. Lauderdale made out of the old treated lumber & never had a problem then either. I'm sure the pesticide residue on vegetables from the store are far worse for you than anything that leaches off the landscape lumber.
I just finished building a raised bed last weekend. We are going to try what is called Square Foot Gardening, using a mixture of peet moss, vermiculate and compost. We are doing a variety of veggies with the summer squash and 'mato plants going to grow vertical. This was built out of cedar and I have roughly $150 in material with it being 2'8" off the ground and a 4'x8' dimension.
I was concered about the depth also but a buddy did it the year before and had no issues. He did vertical like we plan on doing so that will add stability to the plant also. Pretty much the roots will grow more out then deep.
Guess we will see what happens!