Raised beds part 1… planning and groundworks

There was quite a bit to building my raised beds so I am splitting it into two posts so as not to bore you (or to bore you twice, depending on your point of view).

In a previous post I rambled on about my decision making  process on what to build the raised beds from. Now I had to decide how to construct them.  I know my way around a cordless drill and a saw, but I am no DIY guru, and I had to deal with a sloping site.  So I set about exploring the Google tubes for some simple plans…. and I found some excellent ones here. I won’t repeat the full instructions, but basically here’s what you do:

  1. Build a simple box frame where you want the bed
  2. Prop it up so that it’s level
  3. Hammer some corner posts in, and screw the frame to them
  4. Fill in the gaps underneath with timber that is cut to fit
  5. For long beds, brace the middle with metal bars to stop them bowing out when filled with heavy wet soil

I decided to plan the dimensions around the size of my sleepers (2.4 m long x 20 cm deep x 5 cm thick).  This reduces the amount of cutting you need to do.  Also, a 1.2 m wide bed – half a sleeper – was pretty much exactly what I wanted anyway.

Next I used Visio to draw up a scale diagram so that I’d know it was all going to fit, and exactly how much timber to buy.  I wanted a long bed down the whole 10 m southern fence line of the back garden, which faces north and is in full sun for most of the day.  This is to grow espaliered fruit trees in.  I have read that espaliered (dwarf) fruit trees should be spaced about 2 m apart, which meant I could fit in 5 trees along the fence line. I decided to squeeze in one more tree by making the bed into an L shape, with a short 2 m section as the bottom of the L.

The fall of the ground along this fence line is around 60 cm, with the higher end at the back, so I had to cater for that in the plan. I basically made a sort of terraced bed of 3 sections, each one dropping by the depth of a sleeper.

Espaliering requires solid posts, between which you run wires that the fruit trees are trained on.  Since they have to support the weight of the (hopefully) fruit-laden branches, the posts and wires need to be strong.  So I went for 3 m long, 10 cm cross-section posts, which I concreted into the ground every 2 m.

Apparently post holes for concrete should be 3 times the width of the post (30 cm) and at least 60 cm deep.  Now, I didn’t fancy digging 7 of these in heavy clay soil by hand, so this presented an ideal opportunity to play with a big boys toy: a petrol-powered post hole digger.  Apparently for 30 cm wide holes you need a 2-person machine, so I duly hired it and enlisted the help of J to bore the holes.  Suffice to say lots of fun was had! And lots of hard manual work avoided.  Here’s a picture of the beast – basically a giant motorised corkscrew:

2013-08-11 12.02.48

And here’s what we did with it:

2013-08-11 12.30.46

Next up was the construction of the frame, but that’s for the next post…


One response to “Raised beds part 1… planning and groundworks

  1. Pingback: Raised beds part 2… Build it, and they will grow (hopefully) | A few less chemicals in the bubble·

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