My soil is rock and DG. I am going to build raised beds, like you, but put chicken wire (1"wire mesh) on the bottom to keep the gophers out - how they live in rock, I'll never know.....

Then I'm going to put down a layer of cardboard - I have a lot of boxes that I saved when I moved - and a lot of mulch.

The DG doesn't have much (anything!) in the way of nutrients, so I need to mulch a LOT.

I've used weed cloth before and it didn't help much. The weeds came up through it and were harder to pull out.

Hermosa, if your raised garden is going to be 18" deep you should not have to place anything on the bottom. I have read somewhere that most vegetables and perennials root system require a depth of approx. 10". Adding Compost to a good soil will be the key I am told. If you use good compost soil, the weeds can be pulled out roots and all by hand. In addition, a raised bed will be much easier to keep up.

I am now constructing my raised beds and looking for some bulk compost soil to fill them with. Good luck to you. vino.

Couragated cardboard or newspapers by the sections made a plenty good 'weed mat' in my measley 6" beds - while being earthworm friendly, and adding organic matter, taboot :)

your bed's deep enough for everything except maybe asparagus - carrots (a notorious deeproot crop) will be no problem at all, and everything else will be spoiled :)

I wouldn't bother trying to loosen up the soil 'under' the bed at all - I'd just put better dirt on top of it, and let nature take its course.

I once used leaves that I had chopped with the lawnmower and piled on to overflowing. I have a clayey soil and this was a good amendment. The small flat pieces of leaf also held moisture very well the following season. After pulling this material aside to plant my tomatoes, I mulched tthem with the leafchop and fond that the moistue they retained naturally resulted in less plant stress and the natural rainfall was enough to keep them watered. Cheap material and most folks want to get rid of leaves and will be glad to give them to you.

Look at Raised Beds for Wheelchair Gardeners about large basket gardens.