I needed some space to plant beans and peas, here is how I resolved this small problem.
Using a car Jack I slid heavy concrete slabs out from a sunny wall, only needed another 4 inches to give me a bed that is now 8 feet long 1 foot wide and 8 inches deep.
The slabs were on top of a gravel bed, so I removed about 3 inches of gravel to get some depth.
I used an 8 foot board from a drywall pallet I had spare from a previous project.
I painted it up and attached 1 foot sides to it.
I stapled heavy plastic sheeting to a baton and attached this to the wall, the whole frame was lined and stapled.
The bottom of the bed was scored for drainage, then filled with a mix of compost and Perlite.
I expect to get many years use from this valuable space.
I saw the weather report today warning of a heavy rain storm moving it so I made a shade with some Paracord and a tarp. the wall is facing the wind direction, so this has save the plants from a severe pounding.
All looks good for the production of food :-)