Building a Polytunnel
In our village almost every house has a small greenhouse. Sometimes they are sturdy constructions made with metal frames and glass or hard plastic windows, but mostly they are hand-built with frames made from either off-cuts of wood or PE piping, covered with a sheet of thick, clear plastic.
Last summer I grew a variety of vegetables in the garden and I was mostly happy with the results. I had a constant supply of lettuce and a bumper crop of courgettes (zucchini), among other things. But this year I want more. I plan on planting larger quantities of basic crops like onions and garlic and a wider variety of vegetables to include ones I can’t easily find here in Lithuania, like green cabbage.
This year I was also determined to join my neighbours in planting a greenhouse. We love tomatoes, peppers, chillies and, of course, cucumbers for pickling. As part of our journey into self-sufficiency I wanted to grow an ample supply of these to eat fresh during the summer and to dry, can and bottle to see us through the winter.
Our garden is quite big so we decided to build fairly a large polytunnel. We weren’t sure we’d use all the space in the first year but we felt it would be a shame to build it too small and then end up having to extend it in future years. The PE piping for the frame comes in a standard length for a 3-metre wide polytunnel, so it was really just the length of the tunnel that we needed to consider. After a little research and confab with neighbours we decided on a 3m x 6m (10’ x 20’) tunnel.
I picked a spot close to the back door (for easy grab-and-cook) that was not shadowed by the house and therefore got sun all day. I staked out the measurements and Arūnas set to work building the frame.
For a 6 metre length we decided on 7 hoops – one every metre. Arūnas started by building a wooden frame around the perimeter. He then drove 1 metre (3’) metal pipes 30 cm (1’) into the ground to act as supports for the PE piping. The PE pipes where then set over the metal pipes across the width of the tunnel. The PE pipes were secured to the inside of the wooden frame with metal connectors.
Arūnas then started work on the supporting structure. He added a wooden frame for the door, an upright support post at the rear and a length of wood down the centre of the PE pipes, again secured in place with metal connectors. Further support posts were added at each end and an outline frame was constructed for the door itself. We decided to add a wooden support down each side of the roof for stringing up our tomatoes and cucumbers.
Next came some digging. The tunnel was not quite as tall as we would have liked due to the fixed length of the pipes. I’m quite tall and have a few problems with my back, so I wanted to be able to stand fully upright in the tunnel. Arūnas dug a path down the centre of tunnel to add an extra 12 cm (5”) of height. He put a wooden frame down each side of the path to create the planting beds, so my “raised beds” are in fact at ground level. We dug a deep trench all around the perimeter so that we could bury the ends of plastic sheeting to fully hold it in place, even in high winds.
The plastic sheeting was carefully laid over the structure and secured to the wooden frame with nails. The door was also covered with the same plastic. A length of wood was added at ground level around the perimeter and nailed to the original (now internal) frame for added security. The earth around the perimeter was pushed back over the ends of the plastic for both security and to create a neat finish.
Now that I had my nice new space I set to making it workable. I dug deeply into the beds to break up the clay, removing roots and large stones. I added 150 litres of peat compost to each bed to enrich the soil and make it a little softer for planting. I added an old kitchen cabinet and some shelving for storage and to hold my seedlings. I also added a few hooks for clothes (it’s hot in there!) and a thermometer to monitor the temperature.
As an afterthought we decided to stain the wood, mostly for protection from the elements, but also to give the tunnel a nice finish. I took an old frame we had built for the chickens (the one I used to keep Beelzebub at a distance) to use as a gate to keep animals out when the door is open. We also realised we’d forgotten to include any ventilation, so Arūnas added a small pop-out window at the rear to create a draught when the door is open.
Although it took quite a bit of work I am absolutely delighted with the final polytunnel. Not including labour is cost €137 (US$155), which I think is an absolute bargain given its size and the sturdiness of the construction.
All that remains now is to plant my seedlings, which you can read about here.
Update October 2016: I have just noticed I had the plastic pipes listed as PVC when in fact they are PE. I had also given two different lengths in the comments. The correct length is 550 mm. An example of the product I used can be found here. Errors now corrected in the post and the comments.