I am not at all an expert in this kind of thing but it worked very well so I share it with you here.
It cost me less than £10 to make.
You will need:
Lots of good quality wood (i.e. strong enough to hold the weight of plant pots and not rotting)
The usual tools like a saw, hammer, plane, screwdriver
Nails and screws
Step 1: The design
I decided to set the shelves in a step fashion so that none would be deprived of sunlight. Note how they come forward as they go down.
It had to be made shorter than this because the longest pieces I had were 2.16m which was still a good size.
The drinks bottles at the one end you see are optional extras that can be attached to grow more plants in.
The 80cm extension at the base it to provide it with stability, in case of winds from behind but it is very open and is unlikely to happen but it's always good to take precautions.
Step 2: Cutting the wood
The first photo shows the shelf supports which were then painted with wood protector. In the middle is one of the floorboards to be used as a shelf.
The second photo shows how I would fix a few pieces of floorboards together by putting another piece of wood under the join and nailing them together. Just a tip for people who might not know about the best technique for nailing- hammer the nails in at angles instead of straight down. This acts as a hook which makes it very hard for the wood to come apart. You'll see an example of this in a later photo.
Step 3: Tidying up the wood
Step 4: Vertical beams
Step 5: Putting it together
I began by making the sides with the shelf supports on. The supports are all 67cm to fit across the posts and leave 50cm between them for the shelves to go on. To line up the posts I laid two of them at each end as you can see then nailed the one at the top on. I left the bottom one resting there while I measured where the others should go so they are far enough apart to leave room for growing plants.
Photo 3 shows putting nails in at angles, which, as I said, stops the wood from being able to come apart.
Photo 4 shows the two ends with shelf supports and the top pieces. The bottom extensions were fitted later.
Step 6: The frame and shelves
Photo 2 shows the middle post added which is necessary to support the middle of the shelves. Three metal brackets were fitted to this, that the shelves would rest on. To find were they needed to go, I rested each shelf on the end supports, held the bracket under it, pushed it up a little (as the wood naturally sags in the middle) and used 2cm screws to fix them in.
Photo 4 then shows how the shelves were placed. I also screwed the brackets to the underside of the shelves to help prevent it swaying from side to side.
Photo 5 shows how the shelves are off-set to allow for sunlight to reach lower down.
I wasn't too pleased about the shelves not being too deep but luckily I had another length of wood that I'd prepared then decided to change so I later added that to the back of the middle shelf.
Step 7: Back in the workshop
I was going to fit two overhangs on to the two front posts and make a big plastic cover to slot into them when needed.
Photo 1 shows the markings on a good thick piece of wood. I sawed most of the lines but in the slot had to saw down the two sides then chisel out the cross line. It came out very easily it it goes along the wood grain.
Photo 2 shows how the plastic beam would slot into the overhang. This plastic was a piece of trunking, which is what you have in houses to hide the electrical wires in. It was 2.5m long so it would be longer than the frame was wide.
I then fixed the plastic sheet (2.7m x 1.8m) by cutting some small pieces of wood, rolling the plastic round the trunking once then screwing them on in four places along the trunking (thanks to my dad for this tip). I did exactly the same at the other end to weight it down and prevent the plastic from being moved by the wind.
Step 8: Getting the last bits on
3: I fitted the overhangs as shown using two long nails, one through the top, one through the front. This is why the wood needs to be thick or it would split it in half. The trunking will fit snugly into these when it's needed and in photos 4 and 5, at the back, you need something to rest it against when it's not needed. I used hooks that were on the fence before and the cover rests well against these.
6 and 7 shows how it looks when it's pulled over. The plastic sheet will sag in the middle so I just made three small holes near the front for the rain to drain through. Otherwise it would get too heavy and eventually tear the plastic.
Step 9: Wanted: lots of plants!
So it was ready to put the first plants on. My mum did us a big favour by growing some spinach, cabbage and peas in her greenhouse and donating lots of pots that she didn't need. You can see how there is a lot of space for many plants and an open area at the bottom for bigger pots. If you don't have many plant pots, you can use plastic milk bottles or other big bottles and simply cut the tops off so the base is a pot. Make some holes in the bottom for drainage and Bob's your uncle. Those bags at the side in the photo 1 are full of bottles we'd collected over a few weeks.
It was appreciated by the women at the charity and I was happy to have designed and made it for almost no money. Now they can grow loads of things and maybe even start their own little market and sell them. :)