The Accidental Smallholder Forum

Growing => Vegetables => Topic started by: glascar5 on September 12, 2009, 11:02:37 pm

Title: Polytunnel Shape
Post by: glascar5 on September 12, 2009, 11:02:37 pm
Hi all,

I know the name suggests a Tunnel, but does it have to be?  Here's my problem... I have three raised veggie beds in my garden already with footpaths around them.  My lawn is split level and they lie in front of the flower bank, at right angles to it.  At the top of the bank is my Garage wall.  (With me so far?)

I'd like to build a structure from the garage wall, so that I can have the existing bank as well as the raised beds in the tunnel.  I can do it quite easily using a timber framed design with three walls and an angled flat roof. (would look like a lean-to) but can I still use plastic for the sides and roof.  Basically I'd use four separate sections of polythene. One for each side and the roof.  Garage end won't need one. 

My idea would be to use batons to secure the polythene in place and then nail these to the frame.  My door would be positioned at the bottom of the bank so as I walk in the bank is on my left and the three beds are on my right.  I never seen one before, but there's always a first.  I could go for the standard tunnel but it seems and awful waste of a bank. 

Any help, advice, admonishing remarks would be greatly appreicated.


Title: Re: Polytunnel Shape
Post by: Farmer on September 13, 2009, 07:23:09 am
Go for reason why it shouldn't work just as well as a polytunnel

Title: Re: Polytunnel Shape
Post by: HappyHippy on September 13, 2009, 09:50:43 am
I second that  ;D
The point of a polytunnel (IMO) is to provide protection and raise the temp inside doesn't really matter what shape it is. As long as it will recieve sunlight, ie. isn't blocked by your garage wall, it will be fine.
Good luck & post us a photo when you've done
Title: Re: Polytunnel Shape
Post by: JD on September 13, 2009, 01:39:13 pm
I would also try to incorporate a vent or two apart from the door to allow air circulation.
Title: Re: Polytunnel Shape
Post by: ballingall on September 13, 2009, 07:34:23 pm
It might be better than a tunnel- at least if you get a hole, you will only have to replace one bit of polythene and not the whole lot.

Title: Re: Polytunnel Shape
Post by: glascar5 on September 14, 2009, 07:56:46 pm

Thanks so much for the replies.  My plan would be to put in two side half doors and the vents would be a great idea (never thought of them) cheers

Title: Re: Polytunnel Shape
Post by: spitfire on September 21, 2009, 08:15:29 pm
I guess it would really be a plastic greenhouse. only issue would be with wind damage and if the side could open to allow air through passage on the really windy days- you shoud be fine. worth a try anyway!
good luck
Title: Re: Polytunnel Shape
Post by: sunnyjohn on September 23, 2009, 10:21:57 pm
Has something similar on the back of my house for a while! I put it there as a very temporary structure when expexting around 30 people for a social gathering, only to find appalling weather forecast for that very weekend. I used sheets of plastic stapled to battens, with more thin battens nailed over them (sandwiching the plastic), and then strips of duct-tape over the top (sandwiching again) to reduce the chance of the threatened wind tearing the thing to shreds before we could use it. We bought some plastic, but as the thing was only ever intended as a one-weekend job, we also recycled the plastic wrappings of a mattress and a wardrobe-type cupboard! Waste not, want not!

After the gathering, in late April, when the lean-to survived not only the weather but also the abuse of numerous guests, it stayed there for the rest of that summer, though the 'front' side came off a few weeks later, leaving the top and ends in place. Opening sections - doors, in effect - replaced the front of the rather hermetically-sealed temporary shell.  It then served as a conservatory for the season.

Yes, it did work like a greenhouse / polytunnel. We reared quite a lot of plants in it, and it provided shelter and a warmer microclimate. Irrigation was an issue, as it would be in any covered structure; you HAVE to water, and regularly and often. And temperature was another consideration; hence the opening doors. Skylights would have been better; some way to let the heat out at the hottest point, and encourage through-flow of air. It was too late for me to design in a better solution, unfortunately, and this was one reason why it's not still there. Planning permission might be another, though it was no effort persuading anyone that it was temporary! If you can contrive some opening vents at or near the top, it would be safer; less danger of cooking the produce before it grows! The temperature at the top of our enclosed space was usually above 30 degrees C, and it often peaked above 50 degrees C! I did lose a few plants as a result. Good preparation for Global Warming....

Good luck,   John
Title: Re: Polytunnel Shape
Post by: r+lchick on October 01, 2009, 05:07:18 pm
Just a quick thought.  If you built your sections like big picture frames; four for the sides and 3/4 for the roof, you could screw the sections together.  This would give you added support and strength in you frame and plastic.  Then if one section goes, you only have a small area to deal with as apposed to replacing a whole side or whole roof.  Just a quick thought. Ros  :-\