Raised Garden Bed Help
I just bought a home and am going to build some raised garden beds. This is my first go at raised beds. I have had traditional gardens in the past, but am new to the world of raised beds. I have done loads of research online and it seems like everyone has an opinion on raised beds, often very contradicting opinions. Not sure who to believe or take advice from. I don't want to waste time and I especially don't want to waste money, as I am on a limited budget. Basically, I just want to be smart and do this right the first time. So...here are my main concerns...
How deep should they be? I was going to build them about 2 ft high, having about 20 inches of soil. Some opinions I have read though say that tall beds would not retain water as easily (obviously) and that you should build them just a foot off the ground. My concern there is many root systems will require much more than a foot of soil to establish themselves.
-What to do underneath beds
Should I dig up soil underneath the beds? In the backyard it is just dirt, with a few tuffs of grass here and there. I am not planning on digging up the soil. I was just going to put cardboard and newspaper at the bottom to help with water retention and worms. The front yard was basically being used as a parking lot. Just a bunch of small rocks that have been pressed into the soil by vehicles. Should I use the same technique there?
-Materials to build the beds with
Opinions are all over the board on this. Railroad ties and other treated lumber apparently are loaded with toxins. Lumber without all the toxins would be super expensive. Concrete would be cheaper but seems like it would get really hot when the temperatures rise, making it difficult to work in the beds. Looking for a cost effective, environmentally sound, and logical solution.
Any advice or suggestion would be greatly appreciated and quickly put to use. Thank you!