I garden in raised beds and I built mine out of western red cedar from the lumber yard. I haven't treated mine with anything as cedar is slow to decay and bugs don't particularly like it. My oldest raised beds are 7 years old and are holding up nicely. If you have cedar trees on your property, you certainly could use those. If you're purchasing dimensional lumber to use in your raised beds, a couple options to treat them to slow the rot is linseed oil or tung oil. Another method is a charring technique by a japanese name I can't remember but you scorch or char the exterior and it preserves the wood.
"Study books and observe nature; if they do not agree, throw away the books." ~ William A. Albrecht
My uncle lives in a dry climate and just uses logs as his bed perimeters. They last for years in Wyoming. In my wet climate, if I used a hardwood I bet they'd last 5 years and be helping the mycorrhiza the whole time. Maybe after 5 years I could just put new logs outside the rotten ones, cover the rot with soil and have a hugel effect...
"Hundreds of years from now it will not matter what my bank account was, the sort of house I lived in or the type of car I drove... But the world may be different because I did something so bafflingly crazy that it becomes a tourist destination"
If you do not want to raise your bed to hip high to not bed down or live in a boggy area, there is no need to build something around a bed. There is no advantage to it other than the weeds like growing were the timber is andthey are hard to get out. I really would save that money and the work. It is a modern habit and I don't really understand why people are doing it.
As just mentioned, do first determine why you need/want to raise your bed.
So I built my first raised bed in a north/south orientation in a south-facing backyard in Toronto, plant hardiness zone 6a/b depending on circumstances. I dug down three feet, buried a couple of large manitoba maple saplings (about 6" diameter at breast) and dropped two years of compost, a yard of composted organic cow manure, some seaweed and shellfish compost, and the soil that had previously filled the hole I had dug. I surrounded the resultant pile with a fence I made out of 2' x 3.5' pallets. My intention was for the enclosure to slant towards the top slightly, allowing my alpine strawberry guild to grow in the spaces between the slats, which actually worked well, for its own part.
Where it fell down was this: I had designed and planted a minimal to no-water bed because I knew that I would be keeping watering to a minimum. When the dry part of the summer hit, because the soil spaces between the slats allowed the air to dry out the whole bed, I had to water it, which I didn't want to do.
So first determine if you really want it raised. If you do, I would think about its permeability. I like the planned deterioration that is represented by fresh cut hardwood that you then innoculate with mushroom spore. If that's not your cup of tea, I would think about something with natural antifungal properties like the aforementioned cedar, cypresses, or black locust.
I have a potter friend, and have been toying with the idea of simply mulching with large pieces of her unglazed clay pottery, with larger pieces rough cut and assembled like you would a mortarless masonry wall, all fitted together to contain a hugelbeet. This, though, would be less about containing the pile itself and more about containing the moisture. I'm sure it would also look fantastic, like a garden gnome massacre.
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-Robert A. Heinlein
Simon Scott wrote:What would be the permie way to preserve the wood in a raised bed? Thank you.
The permie way to preserve wood that will be in contact with soil is to soak it in a borax solution in a ratio of 1:2 for at least 30 minutes.
If you have a way to add pressure to force the solution into the wood (requires a steel pipe long enough and large enough for the wood to fit inside, seals that will hold both the liquid in as well as the air pressure, a valve stem for adding the air pressure from a compressor)
then you can really saturate the wood with the boron contained in the borax solution, this prevents fungi from growing as well as deterring termites.