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Concrete flower bed on raised patio

Hi folks 

We are in process of building patio on raised area of garden.

the concrete is poured on top of steel and 2 inch stone filler as there would be a drop off to garden dangerous for kids we built a flower bed 2 blocks high. What I never considered was drainage for the flower bed. At the front section of flower bed is a full concrete wall below so can’t drill down to 2 inch stone below 

the sides this might be possible if I drill back at angle to but at the front if I drill out front it will drip down plastered wall when plastered. 

Has anyone any suggestions I will post a few pics so you have an idea 

I was thinking of building another bed halfway up front wall and drilling out then so water can drain into this bed 


  • If you put a layer of rubble in the bottom to the height of where you can drill drainage holes then it will act as a sump (assuming it definitely holds water). This will let the roots grow down into the water but if you do it right not make the soil really wet. You can buy pots that do the same thing and they are excellent for summer bedding as they reduce the need to water. 
  • Lizzie27Lizzie27 Bath, SomersetPosts: 8,209
    edited 23 November
    I think if you can drill a few holes at intervals into the mortar  between the blocks at the lowest level possible, that would drain okay. They don't need to be all the way round.

    We've got a kind of stone walled/mortared raised bed on a concrete based patio and I've never noticed any water draining out the holes nor waterlogged soil. Not sure where all the rainwater goes, perhaps the bamboo soaks it all up.
  • JennyJJennyJ DoncasterPosts: 4,883
    Are you gong to render and paint the blocks? If you are, it might be worth putting some lengths of plastic pipe into your holes (something like cistern overflow pipes) so that the water that drains out drops onto the bed below and doesn't run or drip down the face of the wall and stain the paint. It's not something I've tried (no raised beds here) but I'm sure there'll be someone on here who knows more about building and could tell you whether it would work. I think @Wilderbeast is a builder (sorry if I've got that wrong and tagged you for no reason).
  • Thanks yes planning on rendering wall I know I will need plastic or liner I. The bed as we soil will eventually work through concrete and have an effect on plaster. It’s just usually soil that’s not connected with soil and is in concrete planter would usually need overwatering to keep plants growing I don’t want holes out the front wall visible as drainage My real question I suppose is it completely necessary for drainage holes? The chances of bed over filling would want to be serious amount of rainfall am I wrong?
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