How Do You Separate Lava Rocks From Topsoil, Without Losing Soil?
The screen thing is the only way. I had this exact issue with a house where I wanted to put a 2-foot wide planter area up against a retaining wall. But, the people who owned the house had put aggregate gravel all around before planting the grass that was there. One thing about making a screen for this is that you can’t just make a 2×4 frame and then staple a screen to the top of it. The action of rubbing the dirt along the screen will eventually cause it to bow in and become disconnected from the frame. You have to cut the screen such that it has flaps that you can wrap all the way around to the other side of the frame and staple it there. That way, the staples will hold the screen in place better. Also, use the kind of screen with about 1/2-inch square holes in it. Any bigger than that and you won’t be able to effectively sift out the rocks. Any smaller than that and the dirt will clog up the screen. For the moisture problem, one solution is to position the screen over a couple of saw
