raised beds

[paulab]

Can someone put me right please I use to think that raised beds just kinda sat on top of slabs and gave a bit extra growing room - but now I kinda get the inclin' that I was wrong! What I'm after is an area which is 'raised up' so on bad days I can still get out and do stuff - but also an area for hopefully growing vegetables. Do I have to lift the slabs and dig and prepare the soil before building up the raised bed? Any suggestions gratefully received
Paulab

[ClayGarden]

I thought raised bed were more to help/save bad backs, and lift above waterlogged clay bed. But i guess if you build one on your patio it would be fine, just a very large container. I presume you would have to do something about the drainage though otherwise it would slowly fill up if there wasn't any.