[TomatoDon]

I've tried many sizes, and a 5 x 12 with a 5 foot path has worked best for me. For ease of use, for for the older and younger to enjoy, a bed 24 inches high is ideal. There is very little stooping. The problem is having a good supply of cheap, bulk organic matter to fill it with.

One year I bought square bales of hay and used that as my bulk filler. I added bagged organic matter and regular ole Mother Earth topsoil to finish filling it. During the season it will settle, so you will have to add more of everything the next year and maybe the next until you get it stable.

Most farmers will let you have pieces of broken or rotten big round bales that have fallen apart. I see literally mounds of bagged leaves in neighborhoods that also make good organic matter. Some cities pick up leaves and sticks and tree limbs and grind them up and give it away to residence wanting organic matter for their gardens. Just don't try to fill it all with store-bought sacks of organic matter because you will be amazed at how many bags you will need and what it will cost.

I used treated 2 x 12 x 12's. They are safe to use and there is no evidence that I can find otherwise. We've gone over that topic in other threads here for years. I've tried 4 x 8 beds and found them far too small. Again, my best size is 5 x 12 with a 5 foot walk.

It won't be cheap and it won't be easy, but it will be good. You can't beat a properly constructed, sized, and filled raised bed.

I hope this helps.
DS