Posted: 26/05/2013 at 21:47
That is fair enough, if you cant remove the rubble to make the soil usable then a raised bed seems a good alternative. Not being one to buy things ready made I can't recommend a supplier, but only advise that whatever you choose is not too wide so that you can reach the centre from each side and is made of decent thick treated timber. I know that some people dislike using treated timber with veg, but the investment is not inconsiderable so anything to prolong the life of the bed is probably a good thing.
Do research the cost of not only the bed but the soil with which you fill it as this can be expensive, and consider the effort involved in moving it.
(If I were to build a raised bed I would be using treated timber 2inch by 8 or 9inch for the sides, doubled up to give a depth of 16 to 18 inches and then support the corners with 3inch posts. Again this could be obtained from a timber yard and many would be able to cut to length and pressure treat for you.)