building a veg bed on concrete???

pip7

Hi - about to build my first veg beds. My question is that I am building on a slab of concrete in my back garden - I have room for two beds with paths between - beds will be 1.2m wide by 3.5m long. My plan is to lay a course of brick for each (like a little plinth), infill with stone for drainage, overlay with weed control material (to stop soil falling through), then build the sides of bed with timber and add my soil.

My question - is this the best way? I am assuming that I can just put the soil straight onto the concrete slab?? and that I do need to go to trouble of creating my drainage system underneath???

Also someone suggested that I could just build my timber bed with a timber bottom to it and lay that directly onto the concrete slab? would this work? my instinct is that there wouldn't be enough drainage with this???

anyone built a bed over a concrete slab have tips? one final question - how deep should the soil be - plan to grow spuds, carrotts, onions - usual basic veg??

also just to mention it isn't an option for me to take up the slab.

thanks

mp22

If you lay bricks on the concrete bed where's the excess water going to get out?Some form of dranage will be required.depth of soil 18 inches should be enough,

pip7

Thanks MP22 that was quick - re the drainage I was planning to leave say a 2inch space between bricks to allow excess water out (i.e. little gaps between some if not all the bricks as I lay them) - the water has room to run off as there is space round the concrete slab in the garden - gravel paths. Do you think this would be ok?

Thanks for the advice on depth - was planning on using 2x9inch boards to build so 18inches is perfect

mp22

large gaps between the bricks will let the gravel escape more smaller gaps (smaller than your gravel)might be the way to go.Also 3.5 meters of 9x2 will need to be stiffened in the middle to stop it bowing out along it length.

pip7

Thanks again mp22, that's fantastic help. Looking forward to getting started this wknd.