Answer: You can build a raised bed over an existing lawn but the first thing you'll want to do is dig the earth where you're going to be mounding up the soil for the raised bed. If you simply cover the existing lawn, the bed may not drain because of compacted soil. You won't need to completely dig out the lawn, just roughen up the soil surface before putting the soil over it for the planting bed. Most vegetables will grow well with just 18" of root room. You can build your raised bed with only 12" of new soil, as long as you've broken the surface of the old lawn to veggie roots can penetrate. Best wishes with your new veggie bed!
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