Q&A for How to Build Raised Vegetable Garden Boxes

A minimum of 6 inches, depending on what you are growing. Tomatoes and carrots, need more. Cilantro and lettuce will probably be okay with just 6.

Perhaps, or maybe consider filling the bottom to a level surface with river boulders or similar.

General compaction rate for most garden mixes is between 25-35% depending on how loose it is when you add it and organic matter composition. If you compact it with your feet you'll achieve close to this right away. Unless you're the weight of a small car, this one off compaction isn't enough to stop root development or water holding capabilities. What you don't want is to plant your veggies and find the roots exposed two months later when it compacts and settles on its own.

2x4's are generally less than two inches thick. So, it'd be safe to go with a 2" wood screw. However, the wall planks do not need to be 2x4's, you'd have 4 inches of depth for your garden! A better option would be something more along the lines of plywood that could be stripped down to maybe be a foot deep or more to allow for root growth and stabilization. Were plywood to be used, inch and a half screws would be perfect.

Yes! Do not do it. Don't use pallets either, unless you know that they have not been chemically treated with something.

Seal the wood with either a transparent waterproofing stain or one with color. Most fence or deck stains with a built-in sealer will work for this. Most stores offer transparent, semi-transparent, or solid color stains. Adding color to the stain also gives the box some character.

It most likely doesn't matter. As long as you add the right amount of soil and plant in the correct season, you should be good to go.

No. The idea of the garden box is to better control your soil and prevent weeds and pests. Build them at a height that's ideal for the length of the plant's root, filling it with a good soil mix for that type of plant.

Yes, you can.

Sand will do the opposite. Add organic matter if you wish to retain more water.