Polytunnel query

[Alexandra]

I would really like to get a polytunnel for our vegetable plot, as it is on a very exposed site (this year I lost the first lot of sweet peas because I didn't put up a windbreak), but having looked at various websites, I now have no idea about what polytunnel to get.
I mistakenly thought that a polytunnel was a polytunnel, but now I find out that I can get different diameters of metal frame, different types of polythene etc etc. Can anyone shed any light on what the best option is and if there really is a difference between all of the different specifications?
All help much appreciated,
Mary.

[Green Rosie]

Hi and welcome.

I used First Tunnels (www.firsttunnels.co.uk/) and they were able to talk me through the whole process. They can also send out a detailed booklet. My new polytunnel arrived just before Christmas so yet to get it up and have to admit to being a a polytunnel virgin too

[Camile]

Hello,

We had a hard time decided wich one to get indeed ..

we went thhrrough firsttunnels too ...

The only thing I would recommend is to get a high sided one, and some crop bars ..

Good luck,
Camile

[Thurston Garden]

Mary - if it is possible to position the tunnel in the lea of a hedge or some trees then this will give it good shelter. Not too close so as to be shaded, nor go green with tree pollen though.

I think the key is to ensure your ground tubes are well fixed in - ours were done like this (first tunnels too!): for each hoop, there's two ground tubes, one at each end. Ours were about 2 and a half feet long and of 65mm diameter tubes (very large tunnel mind!). We dug a square hole about 18" deep and 18" square. The ground tube was knocked into the ground in the centre of the hole. An exhaust bracket was clamped around the tube at the bottom of the hole. Then an anchor plate (a 15" square sheet of galvanised metal that has a hole in the centre slightly larger than the tube diameter) was dropped over the tube and then lay on top of the exhaust clamp. It was then secured to the tube by placing another exhaust clamp on the top of the plate. This way, the plate is fixed to the ground tube between the two clamps and when the hole was backfilled and the soil thumped back into the hole, the tube cannot ride up and down in the soil (this happened in the first year with our small tunnel where the tubes were just knocked into the soil and the frame hoops fitted on the top.)

With the ground tubes fixed firmly in the soil (concrete to backfill the holes may be an option if your soil is light) the frame hoops can be added. As previously mentioned, crop bars are a good idea - not only to they give the tunnel rigidity, they also provide a useful fixing point for strings and a place to hang baskets etc from.

The third, but probably most useful thing is to go for timber base rails. don't be tempted to do the cheaper option of trenching the polythene into the ground -with the timber rail, not only does it make a neater job but you can tighten the polythene regularly because it will slacken as it settles, or the frame settles. The only down side ir it provides a place for the rabbits to get in, so try and seal it up!

Some of my tunnel pics here and here

Go for it! Tunnels are fab! Sleepless nights though when it's really windy, but it's amazing how much of a battering they can take!

[Alexandra]

Thank you everyone - I've got the first tunnels booklet, so will go back through it now. I haven't looked at the pictures yet - will get Simon to look at them seeing as he's going to have to do that hard work!
Hope you all have a good New Year

[maggienetball]

I'm another first tunnels customer. We put ours up on a windy site so paid special attention to which way it was placed.

I agree thta it's good to give it some protection from wind if possible. We didn't use concrete but used the marvellous anchor plates and have never had a moments trouble.

I was given very good advice before buying the tunnel. Spend your money on the width rather than the length as you get more growing space.

We have crop bars too and they're a great stabilizer and very useful for so many things.

We also went for the widest doors at both ends cos oterwise you can't always get a wheelbarrow in easily.

We installed their irrigation system - which is a blessing and so easy to use.

And finally we fitted their own ground sheet to 1/2 the tunnel (really thick and great value for money). We have covered that half of the inside with pea shingle and boarded up slightly raised beds on the other side which we keep as open ground. Purpose of this is that you water the shingle and it keeps the tunnel humid, which is what plants need. Gives you lots of pot growing area too. Frogs and toads love it and live in the tunnel all year quite happily.

We love our tunnel. Hope you get as much pleasure from yours too. Post some pictures when you get it up!

[Smooth Hound]

I have 5 tubes and have bought the polythene for my polytunnel, which i will be putting up this yr, iwas going to dig it into the ground, but have just seen this about a wooden rail, could someone explain this to me or even show some pictures/drawing. also i am not certain how far apart to put the loops /bars, it is 14 ft wide and not a storm one the bars arent massive in diameter i think tey are 32 or 35mm , my garden is reasonably protected, i want to make the polytunnel as ong as i can get away with, but i dont want it to blow away, if any one can advise me on this.

[Thurston Garden]

I really should take some photos (edited to include photos!) of this but will try to describe in the meantime.

A plank of wood is fixed horizontally at the base of the hoops. About 4 inches from the ground. This is clamped to the base of the tubes and is on the outside of the frame.

Along the front face of this plank is nailed a batten half the height of the plank. A 50mm deep plank gets a 25mm batten nailed the full length of the plank keeping the top two edges flush.

When the polythene is pulled down over the front of the batten, it is then secured by a second batten with the polythene trapped inbetween in an S shape. The polythene goes over the front of the top batten, under the underside edge of the top batten and down the bottom face of the plank. When the bottom batten is nailed on the outside this traps the polythene tightly.

When it's done you can see the exposed bottom batten with the polythene protruding down between it and the plank. The pool of water with leaves is caused by the excess polythene lying on the ground surface.



You also see the top batten which is inside the polythene.



You can then adjust the clamps on the inside and push the timber base rail down to properly tension the polythene.

Much easier than it sounds and adjustable which trenching is not. Your tunnel will sink into the ground eventually, unless concreted in or is fitted with big anchor plates. As it sinks it loosens the polythene.

[Thurston Garden]

Sorry forgot about hoop spacings!

If the site is very sheltered you could probably put them at 8ft spacings giving you a length of 32ft. If it gets a fair wind then you should put the hoops closer together, say 6ft. Closer if it is really exposed.

A 32ft by 14ft tunnel is good size. no matter what size you eventually make it, you will wish you had made it bigger!

It may be worth thinking about adding crop bars. These are the horizontal roof bars which fix across the upper part of the hoops. These are great for hanging baskets of toms or bunches of onions for drying, for tying up tomato cordons and also give the tunnel better strength - they stop if flexing too much in high winds. You cannot fit these easily as an after thought so if your budget allows, add them now and you can justify the extra spacing on the tubes.

Keep us posted on progress. I will take some photos if you will lol

[maggienetball]

First tunnels recommend the spacings at 5ft for an exposed site. That's what we have as our site is very windy.

The wood base board and batons are brilliant and we used them too, rather than burying the plastic. We got hold of a staple gun (upholstery kind) and held the polythene in place along the wood with staples before fitting the batten on top of it. Less fiddly that way, and you can adjust the tension as you go along. It doesn't tear as they are just staples and the polythene is really thick. Sides first and ends last. Staples really hold the plastic round the door frame too while you're trying to batten.

Keep us updated.

[maggienetball]

Actually, if you go on the First Tunnels site, it shows you how all the parts work and how far apart to space everything. It also gives an assembly guide.

Best to check that out as you don't want to run out of plastic after putting all the hoops in place.

Also very important to make sure the tunnels "square" (measure the diagonals) otherwise the doors won't hang properly or may not close. Also plastic won't fit everywhere. This is really best checked as you go along. We had to dig up 4 anchor plates and move them because we hadn't gone the angles right, even though we'd got the distance right.

As long as you follow the manufacturers instructions, the tunnel should be easy to erect properly.

[Smooth Hound]

Ive just had a look at first tunnels, they describe how to put one up by digging it in , but i cant find anything on the plank/board way

[Smooth Hound]

Ive just had a look at first tunnels, they describe how to put one up by digging it in , but i cant find anything on the plank/board way

[Smooth Hound]

And the clamps, what sort of clamps would be suitable

[Thurston Garden]

Exhaust clamps are best. I have added a couple of pics in my earlier post which should help.

My main problems are with my doors - they have blown off twice in the past and blew open on Friday night/Sat morning. I have lost count on how many hasp & staples I have fitted only to have them broken by the force of the wind.



My most successful means of keeping them closed is with 2 fence posts along the bottom and my zig-zag harrows in front of them. I need into the tunnel on a daily basis and it is a pain moving them each time so I am considering getting some brackets made to hold a long roof joist along the front of the doors like you see on the movies lol.



The funnel flexes a lot in a high wind and the door lintel lifts up and down allowing the door bolts to pop out of their housings (all 8 of them eventually). Once they have popped out, the full force of the wind on the doors (8ft tall by 16ft wide) is taken by the hasp and staple which disintegrates and the doors blow open.

I was very surprised to see they had blown open when I went up yesterday morning, but was thankful there was no damage done - I wonder what would have given if the doors had not.......