Posted: 29/01/2012 at 11:53
This is a great idea. But practically there are problems. As one of the people who've actually built one of these - following the instructions - the design really needs a drainage outlet, or if you follow these instructions proper lining. While the wall looked fantastic for the first 4-6 weeks, I'm now having to deal with the issue of water penetrating through the render and through the blocks after the soil and plants went in. The water penetration is showing up as efflorescence (a white powder that shows on the surface of the wall). So I'd fully recommend that you seal the render or line the inside of the wall - and decide against "Only render halfway down the inside of the bed, as the soil will cover the rest. "
I've not fully stopped the problem. So I'd suggest other people considering the project do investigate this further. Prevention is better than a curse!
I'd also suggest if you are considering this project, seriously price up the soil you'll need to fill the bed - and then once (even after stamping it down) let the top soil settle before planting and then top up with more soil. You'll be amazed at how much soil you'll need.