Raised beds on concrete surface

[BarkingUpTheWrongRoseBush]

We've got an old garage base which I could break up but I'd rather not.

Anyone any experience of putting raised beds on a concrete base. I'd make them pretty high. But wondering about drainage....would you line them then put holes in the liner. or just pile in compost/manure etc.

I would make them quite tall and put rubble, or similar in the bottom and make some drainage holes in the sides at that level. I don't line my raised beds.

I'd line round the edges if it's made of wood, just to keep the worst of any damp compost off the wood and help it last a bit longer. I wouldn't line the bottom.

re drainage, I'd fill the bottom 25% or so with rubble, stone, gravel - whatever I had to hand that allowed free drainage.

I've seen people drill holes through the concrete pad to aid drainage but I don't know how effective that is.