I am in process of building the raised bed. I have got couple of questions:

1. I bought untreated 2x6 cedar wood planks and I am planning to build a 1 feet high raised bed. I will be filling this with 3-way topsoil. Wondering if I should remove the dirt from the underneath and replace it with the good top soil? Or 1 feet of good soil is enough for most vegetables.

I want to emphasize that ground is hard and there is no good soil (lot on gravel and concrete). Usually how deep is good for most vegetable in our region.

2. Should I stain the wood before putting the soil inside? If yes what kind of stain I use? Oil based or water based.

I am in Seattle area.