Talkback: How to build a raised bed - Page 3

could I use treated gravel boards for a raised bed to plants vegetables as I have heard the chemicals used could be harmful
Thanks

Hi a4, See the other thread you posted on, regarding safety.  I actually have used pressure- treated gravel boards for some of my own raised beds, but be aware that soil is very heavy (particularly when wet) and standard 19mm thick gravel boards aren't really strong enough.  I used a double thickness of them, overlapped so that the long edges of each plank aren't in the same place, to help prevent bowing.  You'll need to have strong 2" (50mm) vertical stakes at the corners and at about every 400mm along the length of each side to support the weight of wet soil behind.

Thanks Again Bob i hope to start this project in the next few weeks

What is the optimium height for a raised bed? I am looking at some corrugated metal sheets (1m x 0.5m x 1m x 0.5m) with each corner secured by a metal flashing to neaten off the edges, and a small flashing over the top again to add extra strength to the structure & to provide safety edges

The depth (width of the sheets) currently gives me a total height of 2ft, obviously I can embed some of this in to my garden, but am just wondering if any one considers 2ft too tall for a raised bed or should I be looking to slice the sheets in half and go for a raised bed of 1ft ? 

It doesn't really matter, Fiona, but to benefit from the improved drainage at least a foot high in my opinion.  Probably the most important consideration is the amount of soil etc you will need to fill them.  Twice the height = twice the volume.  The taller they are, the easier they are to tend though, so less bending and stretching required!