I am getting ready to rebuild my raised beds. Old beds were 4x4's in the corners with 2x10's on the sides. Pretty basic! I'm taking a little bit different track on the new ones. I'm planning on stacking 4x4's something like this....
My beds will be 4'x8' and 4'x12'. I am planning on going up 6 layers for a full height of 21". Corners will be overlapped. Each side will be a single piece (except at the overlapped corners).
1) Would it be better to use screws or nails/spikes to tie the levels together?
2) Would it be a good idea or a bad idea to also use construction adhesive to really tie it together. Kind of concerned about this as I'm thinking that the timbers will want to expand/contract independently. But I think they should be "connected" in some manner for the overall structural integrity.
I am using 4x4's instead of 6x6's due to the overall cost. I have a total of 6 beds and using 6x6's would add right at $900 to the overall cost of this project. I can buy a lot of veggies for $900!
I am using treated lumber for the beds. Although the newer treating techniques claim it's safe for food gardens, I'm still not crazy about it. BUT, I am also putting a 35 mil thick food grade plastic liner between the soil and the lumber to isolate my growing medium from the treated lumber.
Using cedar instead of treated would add around $450 (assuming 4x4's).
I am going 6 layers / 21" tall to accommodate Sweetie. Due to some medical conditions, it's getting harder and harder for her to get up and down. And I ain't getting any younger myself. I kicked around 18" vs. 21" tall and opted for the higher bed. Once I build 5 layers, I'll take a look at it and make a final decision.
Any thoughts on screws/nails and also about using adhesive would be appreciated.