Pallet wood raised garden bed design considerations...
OK guys, I don't' want to pretend to state that there in only one way to make a pallet wood raised bed, but recently I came across a YouTube video where a young lady was talking about all her "mistakes" in design of building her raised beds out of pallet wood. I'll link to that video a little later. But first, let me show you what I consider a good design for a pallet wood raised bed and what makes this type of design better than other options.
What I want to call attention to is the 2X4's frame on the outside, and the pallet wood slats on the inside of that 2X4 frame. There are a number of advantages to this design. First of all, the 2X4's are screwed together with GRK fasteners in his build. Here is a nice picture of the type of screw he is using.
Notice that top of the screw head has a built in "washer" to add additional strength and holding power to fasten one 2X4 into another. You could do the same thing with a regular screw and washer, maybe even less expensive, but the idea is that the washer provides lots of additional strength to the frame compared to a regular screw and narrow screwhead. So, in the first place, your raised bed frame is going to be rock solid. You can do the same with nails, adding a washer to extend the nail head for more holding strength.
Next, I want to point out that the pallet wood slats are attached to the inside of that 2X4 frame. There are a number of advantages to that design. First of all, the raised garden bed soil can get heavy, and it pushes out on the sidewalls. If you have the rock solid 2X4 frame on the outside of the build, then the pallet wood slats on the inside are held in place by both any nails/screws you used to fasten the side pieces, but also by the outward pressure of the soil in the raised bed. That is important to consider.
If you fastened the pallet wood sidewall slats on the outside of that 2X4 frame, the weight of the raised bed soil and the outward force on those slats would weaken their hold over a much shorter time period and you would have what I would call "blow outs" when the wood deteriorates and the planks no longer hold on to the frame. You can see that problem in the second video I will link to about mistakes she made in her build.
Another advantage to using the slats on the inside of the 2X4 frames is that you can use lots of boards that are not quite the same height. All you need to concern yourself is that the top edge, which you see, is aligned. The bottom edge of the boards, which you cannot see, are covered by 3-1/2 inches of that outside 2X4 frame. That gives you a good 2-1/2 to 3 inches of room to use those shorter plank pieces you might have laying around. Have I done this? Absolutely. And you will never know because you cannot see it at all behind that lower frame.
I normally make my raised garden beds and planters 16 inches tall. With the 2X4 frames on the outside, I was able to use any of my shorter pieces 13 to 16 inches tall. I cleaned up lots of scraps in the wood box on one build alone. Don't throw out those shorter pieces! You might find a good use for them!
Now for the "mistakes" video I was talking about. This lady is providing a 3 year update on her pallet wood raised beds. They are falling all apart after only 2-3 years. She is pretty hard on herself. It's not the pallet wood that was the problem. It was how she built the raised beds, or the design of the raised beds, that failed her. Although I am not a carpenter, I was easily able to see how her intial design of her raised beds would not hold up over time. I'm sure they looked just fine when initially built. But she made a number of mistakes that she will talk about so you don't have to make the same mistakes she did. I think it's brave for someone to share and show their mistakes so others can do it better. Anyway, here is the 5 minute video of how not to do it....
One thing she mentions in her mistakes video, is that she would put a plastic liner inside the raised bed to protect the wood from rotting out so fast. That is an interesting idea. If you can protect the wood sidewalls from direct contact with the wood planks, I imagine your boards would not deteriorate as fast. In another thread here on the BYC forums, we were discussing if stapling those empty feed bags to the inside of a raised bed would help protect the wood sidewalls for a few years longer. I know some of my empty feed bags have a plastic-like feel to them. They are not all paper. And, I would think, they might last a little longer as a liner. Tell me what you think.
Also, I would appreciate anyone suggesting a non-toxic way to "treat" the pallet wood in a raised garden food bed to help the wood last longer. I have avoided any treatment of the wood at all because I grow food in my raised beds. But if there is a food-safe way to add years of life to my pallet wood raised garden beds, then I would love to hear about it. Thanks.
That sounds interesting for the exterior wood of a build. I don't see how you could reapply line-seed oil to the inside of a raised bed that is filled with soil. I think any treatment for the inside of the raised garden bed is a one time application.
The feed bags I get are some kind of woven plastic. I've made a couple grocery tote bags, and also the flags on my fence. The flags have been on the fence in the weather, and other than fading, they've held up really well. I hadn't thought of using them as "grow bags," as I didn't think they'd break down. What brand of feed do you buy? Maybe yours are more paper based...? 
