Raised Bed Question

Hi all!

I'm trying to create a vegetable garden on the premises of an Artist / Creative Studio group I'm involved in.

We have a south-west facing paved area at the front of our building which is approx 30m x 8m in size. So a good sized location, with plenty of sunshine when we get it.

I've lifted a few of the paving stones and they're laid on at least 50cm depth of clean gravel hardfill, so there's no mission of digging down to soil. Drainage is good in the area. We get plenty of rain, and it always gets away to ground easily.

So, my questions!

1. What are the general thoughts on lifting areas of the paving and building raised beds on top of the hardfill?
2. Assuming the above is not a shocking idea, can anyone recommend a permeable membrane to line the bottom of the beds to separate them from the hardfill but to allow drainage.
3. Can anyone give any advice on the minimum depth of each raised bed. We hope to grow a good selection of vegetables suited to our climate. I'm assuming given the limitations of our location deeper beds will be required for root veg, but any steering I can get on this would be good.
4. Is there anything anyone would strongly recommend against trying to grow in this location, given that the bottom of the beds will never meet soil below?
5. We have a supplier who can deliver bulk ready mixed loads of 65% screened topsoil, 5% sharp sand and 30% of fine organic compost. Does this sound like a sensible starting point for filling the beds.

Many, many thanks in advance to anyone who can weigh in on this!

Neal

 

The only problem I'd see with building on top of hardcore is drainage. Depending what the hardcore is, how deep and how compacted, it could hold water. I would chuck on a couple of bucketfuls of water and see how long it takes to disappear. Water will only build up in the bed if it can't get out the bottom or sides.

This link might help with soil depth requirements for vegetables, to establish the depth of your raised bed:
Raised Beds: Soil Depth Requirements

 

I will be creating my first raised bed this year hopefully, so can't help you regarding issues with drainage or hardcore Neal, sorry. My bed will be going directly onto soil. Below is an idea for your root veg, the upper tier giving you depth for those, with access at the back to make working it easier.

 

My raised beds are sitting on top my sod which is on top of clay. It is 11 inches deep. I've grown brussels sprouts , onions, peas, beans, lettuce, cannabis, tomatoes, and on and on...

To this day, I still cannot figure out why things like Kelsae onions need more than two inches of soil... but I digress.

I laid weed barrier cloth before adding the dirt.

If you have good drainage , you can do anything!

I am one of those perpetual newbies who loves the look of flowers and things but I really enjoy growing things that give me something back. Oink, oink...

Get rid of the pavers and get growing!

 

I love how you casually drop in cannabis to your list of otherwise ‘regular’ veg .

 

Sounds like a good start, but make sure you have a good look at this; as screened topsoil can be very variable.
Mypex is one brand of permeable membrane used.
My cousin had some cannabis growing in her back garden and the result was a permanently stoned rabbit (imagine Dylan off the Magic Roundabout).