How to build your own greenhouse/polytunnel...

26 August, 2015

One of the things I have always wanted was a greenhouse. Now while here in Melbourne town we don't have the crazy snowy winters of other climates, instead having a few mere frosts through our winter months, I do find that our summers are not quite long enough to get a worthwhile harvest from some of the more heat loving plants like eggplants and capsicums/chillies.

A greenhouse would instantly solve my problem, extending the season in both directions (warmer earlier in spring, and warmer later into autumn) and allowing me a lot more produce time from said plants.

But they were ridiculously expensive. All the reasonably sized ones were in the many hundreds, if not thousands of dollars. It was then that I looked into the cheaper option of the polytunnel aka hoophouse. But when I was considering this option I had used up all the main spaces in the yard, and had nowhere to put it.

But then I needed move the chicken pen, necessitating the moving of the raised beds which I converted to wicking beds. I then had space to build in. The polytunnel idea then came to the forefront.

I decided to use foodnstuffs method of star pickets and polytube which I was also using for the new chicken pen (now converted into a fruit cage). I however was not going to attempt this on my own, so roped in my lovely long suffering mother to help me build the thing. Thanks mum. I owe you!

The star pickets were spaced 1 metre apart. We used 2.4 m star pickets, banged around 40cm into the ground to give a nice high space, then a measured length (I have no idea how long, we just did the first one and then used it as a template for the rest) of polutube was fixed to each side to create the top. Then three treated timber braces were screwed into the lower side of the polutube arches to brace the structure.

The edges of the star pickets were taped over to ensure they wont pierce the plastic cover.

Then the whole thing was covered in a sheet of greenhouse plastic. Lots of wrangling was done to get it all in place, then the plastic was fixed in place with cable ties. These went easily around the polytube arches. For the star pickets, to ensure the plastic was firmly fixed and risk of tearing was reduced, we put an extra bit of polytube on the outside of the star picket (it nestled nicely into the top part of the 'Y' shaped part of the picket) and cable tied around that.


A couple more smaller star pickets to make an entrance, and a few bricks to hold down the flapping ends and it is done.


It is by no means a perfect structure, but I'm hoping it has a few good years of use in it.

To get in I simply move some of the bricks and move the plastic sheet.


Inside, even on a not too sunny day, it is quite warm.

I've laid out some spare timber sleepers to make paths. I couldn't resist starting to plant into it, so I have moved the capsicums overwintering in the old mini greenhouse and put them in the new and improved model, as well as some bought basil in the middle (I always get basil in pots, not just the leaves, when I have to buy it so I can use what I need and plant out the rest).


I also have put the tomatoes recently sown from seed in this space, to hopefully germinate soon.


As a side note, I've been using chalk pens for labelling plants and they are great, as long as I make sure not to water the labels when I give them a top up.

Both ends haven't been permanently fixed down to ensure that come summer time, when I need extra ventilation, I can roll up the end plastic sheets and have a good air flow through the space. This is from the back end, where the polytunnel meets the fruit cage.


The polytunnel was planned to the left side of the available space to be closer to the deciduous trees and benefit from summer shade and winter sun. This also happened to place the water tap inside the polytunnel space, which was a nice bonus for easier watering.

The overall cost was about $240, which is pretty good for a 4m x 2.8m space.

Having had the polytunnel for just on a week, I can only say I'm sorry I didn't build one years ago. I'm very much looking forward to getting some plants in come spring and hopefully get some early crops!

10 comments:

  1. Wow! What a good job. My poly house (a bought one) is only half that size and so full of propagation stuff that there's no room for growing plants for food. I've just about given up on capsicums because of the short season. Will have to look into building one for myself.

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    1. Cheers. Thanks for the inspiration and ideas. I'm sure mine will fill up very quickly! It was surprisingly easy to build, once all the star pickets and polytube was down that is by far the hardest bit.

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  2. Looking good! Yes, very similar method to Bev's and I always admire her handywork! Just be a little cautious if it gets warm/hot about humidity and overheating. Maybe work out a way to roll the ends up like a sun blind. I learned very quickly a whole crop of seedlings can be wipe out very rapidly. Ha! Just finished reading and you've got that covered, should have known :)

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    1. Haha, but thanks for the heads up anyway. Even my mini greenhouse (now long dead) got amazingly warm in summer, so I was forewarned.

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  3. I've always wanted a greenhouse here, but we get too much shade in the fall and winter to make it worthwhile.

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    1. What a pity, I'm sure if you could make one work there would be no stopping you!

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  4. That is a good looking greenhouse, like you my husband & I built a greenhouse for the same reasons they are way too expensive!! Mine is made made from polycarb and we put a vent in, when I got home from work today the vent was fully open and it was 38 in there I'm going to put some shade cloth on it in the near future.

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    1. Hmm, I like your idea of the thermometer. I would be great to know how hot it actually gets in there. Cheers!

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  5. Good to see Bev's excellent tutorial being used. Might save up and make one ourselves as that would be an extra barrier to the rats ;)

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    1. Yes, assuming the aren't clever enough to use the door or you can put up a rat proof barrier. But from all other sides it looks pretty impermeable. I don't think rats eat through plastic, but I'm not sure.
      Either way, I do think it worth the investment for the potential of earlier crops along. Hopefully it lives up to expectations!

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