I thought that I would do a step by step blog for people who
are looking to build their own raised beds in order to grow food in wake of the
UK Lockdown. Maybe you’ve wanted to do this for a while but never had the push,
but now this is it?
Quite simply, my raised beds are boxes. These ones are on
legs and have a base – neither legs or a base are necessary. I have done it for
these ones as I am in a rented property and I want to grow off the floor,
protect the slabs, and be able to move the beds if needed.
The raised beds I build for work are all freestanding but
without a base, and without protruding feet. These are built as a frame which
are then positioned on the floor; if we need to dig out the ground to make them
level then we do, otherwise we just leave them. We make them like this as one
of the sites is on a tarmac base and we don’t want to dig through the tarmac,
but we also do it to reduce materials. There is also a time saving element to
it as we don’t need to dig holes for the corner posts.
The allotment raised beds are simply wooden frames around a
patch of dirt – initially they were edging boards but I am slowly building them
to be raised beds.
 |
| An allotment bed. You can also see the edging boards of the next bed in front of it |
What you need:
Timber! I use timber gravel boards from Wickes. They come in
6ft or 8ft, singly or packs of five. For work we use Jewsons. You will also
need corner posts. At home and on the allotment I have used smaller wood but
for work I use 75mm square fence posts to make them more durable. Click the
words below to go to the Wickes page for each – I am not sponsored by them but
sure wish I was!
Screws! Screw rather than nail. Do not nail. Screw. Screws
enable you to unscrew to take apart, amend, or fix the bed. Nails require a lot
more effort to get out. Always screw. Make sure the length of the screw is long
enough to get through the gravel board and into the corner post without
sticking out either side. We have used 40mm external wood screws, with a 65mm
in places needed. For work I use 50mm or even 75mm, but only because I use
bigger corner posts.
Drill, drill bits, tape measure, pencil/sharpie, panel saw.
Measure the wood:
Use the measuring tape and pencil/sharpie to measure the
wood to the right size. Use the panel saw as a set square to get a right angle,
which helps you make a straight line across the wood (lie blade of saw flat
across the wood, butt the handle up to the edge, draw along the flat edge of
the blade – the handle should be marked 90° or 45°).
Think about your lengths of wood and maximise how many bits
you can get out of each one. David has made me two raised beds out of 5 planks of
wood, with two surplus bits from the allotment. We used 8ft planks and made
beds 70cm long x 50 deep x 30cm tall (two planks tall). If you are not making
floors for the beds you will need less timber. This step does require maths but
it drastically helps reduce wastage!
Cut the wood:
Use the panel saw to cut the wood. A good tip is to put the
saw at an angle on the corner of the wood and draw it back, then take it out,
put it in the small groove and draw it back again. Do this a few times and it will
help the saw ‘bed’ into the wood, thus making it easier to start sawing. Use the
full length of the saw blade and get a long, smooth straight motion going.
Cut your corner posts. The posts for these beds are 35cm
long so that they are flush across the top but stick out 5cm at the bottom to
make the feet. You don’t need feet. You can also have the corner post flush top
and bottom, or 5cm shorter than the top, or 5cm, shorter than top and bottom –
this last method means that the bottom of the corner post is not in contact
with the ground thus reducing the chance of rot, and it also gives you a teeny
bit extra growing space at the top. This is the method we use at work.
Start assembling!:
It may be easier to get someone to help at this point to
hold the timber together. How you do this bit is up to you – we have drilled
the flat edges of the planks together, AND screwed them into the corner posts.
At work we only screw into the corner posts (mostly to save screws).
I screw mine together so that one end of the plank is ‘outside’
at one end and ‘inside’ at the other, instead of having the two ends inside the
long sides. Look at my amazing publisher diagram to explain:
 |
| Green squares are the corner posts. For long beds (longer than 1m) you might want a central post for each long side which helps to prevent warping and bowing. |
I think that this makes the beds stronger and less likely to
warp over time. We make the whole frame first (all four sides) before attaching
the corner posts. At work, for larger beds, we make the whole side and then
assemble the side panels:
Work your way around and get it all done. We waited a day for
the timber to dry out fully before going onto the next step.
Paint or treat the wood:
This just helps preserve the wood. The stuff from Wickes is
treated timber but I like colourful things, so I use Cuprinol and get some
multi-coloured garden funk going on. You can also use Ronseal – a lot of places
have this on offer at the moment if the shops are still open. My local Co-Op had
some so you can pick it up during your lockdown grocery shopping trip. Get a
good coat on the inside and outside – you may then want to leave it to dry and
put another coat on the outside. In sunny weather this should be dry within an
hour. Don’t paint damp wood!
Wood paint will come off your skin and out of your hair, but it WILL NOT wash out of clothes!!
Line the beds:
Lining the beds is just another way to protect the timber. I
don’t do this on the allotment, but I do it at work. It really does make a
difference to the timber and slows rot down SO much. I have lined my new raised
beds at home as there are gaps in the bottom and I didn’t want compost to fall
out whenever I move the beds.
Fill the beds:
Use anything biodegradable to bulk out the bed – this is the
“Filling With Crud” stage! Use things that will rot down anyway such as;
·
Newspaper cut/ripped into bits
·
Shredded paper – I have used ten years worth of
bank statements
·
Veg & fruit peelings – note the whole leek
in this bed below (oops)
·
Grass clippings, hedge trimmings, bits of
stick/timber
The point of this is just to fill the bulk of the bed which reduces
how much compost you need to use. It is also a great way to get rid of paper
recycling if collections have been suspended in your area, and using up food waste.
For added drainage you can put in a load of pebbles or grit at the bottom which will also weigh down the bed.
Top dress with compost. Before you do this, you may want to
put down a layer of thick cardboard or newspaper – this stops anything growing
up from below into your fresh compost (ie nettles, dandelions, couch grass –
anything in your grass clippings pile). Level it off and voila, a ready to use
raised bed!
The compost level will settle over time both as it compresses
what ever is underneath but as it compacts naturally with rainfall etc, so you
may need to top the beds up next spring.
Raised bed sizes:
Don’t make raised beds too big! You need to be able to reach
comfortably to sow seeds and tend the plants. Overreaching causes back
injuries. If you are butting the beds up against the wall, I’d say not wider than
60cm but ideally around 50cm. If you have access all the way around, you may be
able to go up to 80cm – which is 40cm from each side so easy to do.
For height, that is entirely up to you. The taller you make
them, the more crud you need to fill them. Compost ain’t cheap! Each of my
little purple beds have had two grow bags worth of compost in. Mine are two
planks high – 30cm. Work raised beds are a minimum of 60cm.
You can also make raised beds with a false floor in them so
they look tall, but actually the growing space is only 20cm deep. I have never
done this, but it would use a lot more timber. Remember to brace the ‘floorboards’
so that the weight of the compost on top doesn’t warp or distort them.
Advice:
Happy veg growing!
