[FrostyM]

A friend of mine wants to build a raised bed. She thinks it makes more sense to build it close to her house rather than down the bottom of the garden where in bad weather she has to tread through mud etc. This would involve building it on concrete. Would this be a problem? Would you be able to just fill it with soil or would you need to first put a layer of stones or sand for drainage? Has anyone here got raised beds on concrete at the moment?

[doganjo]

Mine are on hardcore with a thin layer of gravel on top and they work fine. Concrete is more or less impervious though so they could get pretty waterlogged.  Mine are deep ones so i don't have to bend - about 2.5 feet high sides with posts in each corner to attach netting/fleece..

That could be an answer for her - deeper beds, a good thick layer of big stones/gravel/rough sand and she'd need less compost/earth.

[MikeM]

so long as there's some sort of drainage at the bottom (say a layer of rubble with an outlet for the water) then it'll be fine.

[FrostyM]

Thanks for the advice folks, I will pass it on to her. I was thinking a layer of gravel/stones with a few holes drilled into the sides to make sure the water can get out and a good layer of soil on top. I am not sure what height she is planning her beds but will suggest the higher beds and see what she thinks. Thanks again folks

[Lesley Silvester]

Sounds about right to me. I have raised beds but they are all on soil. I would consider having some on concrete if I had the space but would make sure I had adequate drainage. Bits of pipe through the sides would do. If she's building them with wood, she's likely to have a problems with the wood rotting quickly if there isn't drainage.

[cloddopper]

I have 24 raised beds , most are three foot by three foot &  36 inch high raised beds in sets of a six bed unit  set on concrete bases ..

In the bottom course of engineering bricks there is a weep hole every three brick ..made by putting the brick down without any mortar between it and the next brick , this is done on all outer walls . Even with my sprinkler system in failure mode (  on to spray a litre every three minutes )  for three days when it was away on holiday it did not flood the beds.

I filled my beds to the top with fresh stable muck and kept it hosed down each evening till it started to drop then added around an 18 " layer of the mix shown below to bring it level up to the top edge of the brickwork .

The MIX .
A  mix of five buckets of composted coir , five buckets of vermiculite then five  buckets of composted animal manures or composts  from five different types of animals
 IE sheep ,goat, turkey , cow, pig ,chicken , rabbits , fish trimmings , sea weed   , garden veg   ( Horse muck tends to keep the weed seeds in it .) Steer clear of council amenity compost and anything with wood products in it .
The council stuff usually contains all sorts of chemicals & bits of glass & metals
 The wood based stuff is not usually composted enough so until it reached compost stage in your bed it robs the beds of nitrogen that the plants need for growth . 

 As the beds are full of the soilless growth medium they take a long time to dry out but do not get sopping wet which is ideal for flower and veg growth as the moisture level is fairly consistent throughout  save for the top 2 inches which does need a gentle watering every now and then if it starts to dry out with sun or the wind .

 I do have to top the beds up with the mix every year but it's far easier for me to do that than dig a garden with a spade as I have a bust up lower spine , wrecked left shoulder joint  and now two very arthritic knees as well.



 The lawn side is raised ground to make the lawn level along its whole length

[lucan rowan.]

those brick beds look lovely, really productive

[cloddopper]

Yup the beds are exactly that .
It took money and not just a few drops of sweat to get it all done just over two years ago . Now it's al settled and the first flush of weeds have been sorted  it is about an hour a week to tend them and 15 min every now and then to sow and harvest .
They are a godsend to work because of arthritis , spinal and shoulder injuries etc.

[Lesley Silvester]

I would have loved to have had brick built ones but could only afford wood. It's not just the materials but the labour involved. I have a friend who is a carpenter and he not only built them but kindly filled them from the manure heaps. He doesn't charge a fortune either and works very hard while he is working.


Note to self: need to get him in again to make some gates.

[cloddopper]

It took me several years to buy the nine or so packs of bricks etc  out of my project money .

When ever I want some thing I set my self targets to attain , when I reach them I put some money aside to the project.
 I've not gone into debt over it as a result .

My  next project is nearly ready for the off , it is to landscape the remainder of the garden in similar beds so I don't have loads of grass to cut  as I get older and more infirm .