A very informative article, I am hoping to make a raised vegetable bed myself, does it matter that I will build it on top of concrete slabs? I thought if I built it using 2 railway sleepers on top of each other the depth should be ok? I would appreciate any advice, thank you
Braddy183 - I wouldn't use railway sleepers, unless they are different from the ones here in Ireland. The Irish ones are treated with creasote. Plus there are serious H&S risks associated with railway sleepers and the way they are used by the railways. Scaffold planks are good but expensive. You can buy 16ft lengths of nine (inches high) by one and a half (inches thick) and they are good to use. If you buy five of them they will make two 16ft beds. Cost about 36 euros per bed.
Jangra - I'd use untreated timber. It will last for a long time anyway, and you can always replace it when it does rot. Treated timber is treated with chemicals and that's going against the very spirit of growing your own. That said, there are treatments which are certified as being okay, but I'd just go to my local builder's merchants or sawmill and get the cheapest timber I could, so long as it was high enough and thick enough and bring it home and make my own.
At 16ft. you will need a cross brace in the centre to stop them from going bow-shaped but this can be anything really - a piece of 4x2 from a building site is ideal. As for the nails coming out - you need nails at least three times the thickness of the timber. Screws are better but need to be really long. Using one and a half inch timber, you'd need screws 5mm x 125mm or so. Also drill (thinner) holes in the piece where the head of the screw will be. This will help pull the joint together.
I garden from a wheelchair. I've used 2x height link-a-boards (search Net) weed suppressant but free drainiing underlay I use a base layer of coir from dried compressed "bricks" & top up with B&Q multipurpose compost vermiculite. Goodl for salads, peas & french beans (dwarf varieites) and courgettes. I even grew sweet corn last year but was let down by the lack of sun! Veronica & verbena bonariensis attract lots of pollinators. Hope this helps.
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I've heard that treated timber releases chemicals that could be harmfull to our health.
What do you think?
Thanks
Jan