Raised garden as prevention of disease in soil
I only plant tomatoes and a couple of years ago a type of blight attacked my plants causing leaves to turn yellow with black spots and work up the plants eventually turning leaves to fall. Went to garden center and bought a concentrate to spray but was told to move garden. I moved around corner to side of shed (previous plot in back of shed). It was not far enough away. The garden center told me the blight stays in the ground. I wondered if building a raised garden with all new dirt on top would help. Do not really have another spot to make another garden.
Certified GKH Gardening Expert
As long as you have a barrier between the ground, and your new soil then it should be much better. You might apply a thin layer of wettable sulfur to the bottom to kill off any disease starting.
I do believe a raised bed will be much better for your situation.