Raised beds over slabs?

[burritofan]

Gardeners of MN, your collective wisdom please. There’s an area of my garden covered in concrete paving slabs – laid directly on soil, not mortared in. I’m loathe to send them to the tip and Freecycle/giving them away has only led to months of hassle (can you measure them all? do you deliver? I want them but not til 2022, etc).

As they’re not on cement, and there’s about 1/2” gap between them all, can I put raised beds directly on top? Maybe adding some rubble (I’ve got plenty of it...) for drainage, then using a liner so the soil doesn’t drain away.

Can anyone foresee any problems with this plan? Will they drain effectively? They’re too heavy for me to lift and do anything else with and this would cover most of the ugliness, plus they’d act as paths between the beds.

Planning on onions, garlic, tomatoes, potatoes, lettuce, lots of herbs, playing around to see what I like growing and what we’re prepared to eat too much of. Thank you!

I'd suspect they would drain too well and dry out in hot weather.

You could pay someone to take them away. probably wouldn't be as much as you think. I used raised beds for veg but they are big 8 x 12 foot beds and even then they dry out on occasion. They are on soil.

If you put big raised beds in - like ones made out of sleepers - then there's no reason why it wouldn't work and could look really good.

Short answer it would work. I'd put down the liner first, perhaps a layer of cardboard between the slabs and liner, but no reason for it not to work

Thanks for the advice, it’s really appreciated!

That’s interesting about them draining too well. The area is next to where I intend the shed, which will have a water butt, but perhaps I’ll rejig the plan and try to get them on the soil by attempting to move a few of the slabs into a path format. Raised-bed-grown food for thought!

(I don’t want to pay to have them taken away because I’d like to avoid adding to landfill, and also I’d rather save the money for 8,000 roses :)

Ah heck I can't remember what tv show it was - something manor garden, iirc it's in Scotland. Anyway one of the presenters said slabs (exposed) was good to have next to plants as it stores heat from the sun then acts like a radiator and keeps soil warmer during the night to help growth. Maybe worth keeping a few?

One problem would be that the raised beds would have to be deeper to account for the extra soil needed above the slabs, so you will need to buy in a lot.

We had a similar situation. We lifted some slabs, leaving enough in place for a path around the beds. Made beds from sleepers sitting on the edge of the slab path. We lifted the soil inside, replaced with rubble then put the good soil back on top before topping up with compost.

If you wanted to use the slabs you could turn the removed slabs on their side, dig in 6”, and use them as the edging for the bed. Instructions here www.carryongardening.org.uk/files/documents/How%20to%20build%20raised%20beds%20final_Nov08.pdf or just google for some good pictures.

Can you plan your layout so that you can remove just the slabs in the middle of each raised bed, leave the rest as paths and supports for whatever you build your beds from. Maybe use the slabs you lift to line a planting hole for a fig?

My dad buried half of each paving slab in the soil to make raised beds

How deep are you planning the raised beds to be. If it's deep enough for the roots of what you want to plant it will be fine. So long as you are prepared to water regularly/

This it mine on a hard base - but it is very deep

I grow veg in tubs standing on paviors . They're about 15 inches deep and that's barely deep enough.

A waterproof liner with a layer of rubble at the base will turn into a stagnant puddle. The rubble won't help drainage if there's nowhere for the water to drain to. If you want a liner, omit the rubble and make sure the liner has lots of holes pierced in the bottom.

I have large raised beds on concrete that we've had no problems with. Gravel on the bottom, a layer of bark and then lined.