[mapahutchins]

Hi all,

Looking for advice on polytunnels. We are planning to get a ~20m x ~6.5m tunnel on our plot. Got one quote in from Northern but wondering if there are other makers I should consider?

We have a fairly windy site in West Cornwall but we can site the tunnel besides some Cornish hedges and will put a field shelter in to offer some more protection (and some trees but that will take time!).

Anyone had any experience with different types of ground fixings? Trenching versus concrete base? Buried concrete ballast, plates or screws? Any pointers?

Any particular manufacturer or installer you would recommend? We will probably do the install ourselves but...

Any tips or advice welcome.

Pretty vague I know!

 

[Penninehillbilly]

We have a 25x25m should have been 30x25 but we put the hoops 5m I stead of 6m apart. Each hoop is set in deep concrete pads. Also wood doorway etc.
Ours has windbreak up to about 2ft on wood frame, plastic rolls up to allow ventilation.
We put the frame up but had the guys out to put cover on. Paid for itself because they knew how to get it tight, lasted many years. We eventually replaced cover but didn't get it tight enough, it blows up more and has split in places. I have a laurel hedge on the windward side, should be about half the height of polytunnel but got a bit out of hand, shades polytunnel from mid afternoon.
Ours was from Northern,  but they aren't very far from here.

[Terry T]

Ours is 48'x18'. from first tunnels. I largely erected it myself with a couple of extras to help with the cover. Would highly recommend .  Their guides and support service for a self build were invaluable along with tips for getting cover tight. 3 years on and no problems. We used base plates instead of concrete which worked well but needed lots of digging.

[mapahutchins]

penninehillbilly - interesting advice about the tensioning. Northern say they have some kind of system that allows you to move the cover up to 100mm after fixing and that allows tensioning? Maybe I need to read that again!!

Terry T - I liked the look of 'first' and will look at them again as I also like all the self help vids they have.

For the base plates we were thinking of digging a trench and placing the plates in that, dumping some concrete on them and then backfilling the trench. I guess the 'proper' way would be to dig some holes, frame, concrete and then use the pads to bolt the pads too but that sounds like a lot of work!

Thanks for the tips.

[Fleecewife]

Our   Northern has that system of raising the hoops after you've put the cover on, to tension it, but we couldn't work out how to do it  '
Ours (7 x 14 x 4m high)  has base rails for attaching the cover, crop bars, bracers at the corners and from the ridge pole to the crop bars, and is the biggest diameter tubing they do (it's a bit windy round here). Check your nuts and bolts after any big wind for tightness. The hoops are held in the ground by poles fixed into concrete dollies - obviously you have to get your positioning absolutely perfect or your tunnel will be on the skew, then will never be properly tensioned - make sure you're good at geometry and your ground is flat.  The hoops are then fitted into the ground tubes with ring and bolt fittings.


Pay special attention to ventilation, as even in exposed sites the wind doesn't always blow, and the temp will rocket inside.  We have large double width louvres, one above another at both ends, and double doors at one end and a single door at the other, tunnel placed east-west.  The lower louvres are a waste of time as weeds and built-up soil stop them from opening easily, plus you can only grow very low crops under them.


Our first cover blew off in a monster gale, because we hadn't attached the polythene quite right.  With it all now done correctly it has survived storms just as huge.


Don't scrimp on the cover - get the thickest one, anything else is false economy.  Also use the anti-hot-spot tape on all metal/polythene contact, and buy a wide roll of repair tape - it's great stuff, whereas gaffer tape just doesn't work.  We had had all sorts of holes punched in our cover, from a sheep's horns, helpful friend pulling long canes out and going straight through, to the cover bumping into the apex of the greenhouse in a big wind (the frame flexes) but the repair tape holds it together as strongly as before the hole.

[Terry T]

No need for concrete on top of base plates, the plates secure to poles with clips and back filling with soil keeps them in place.
We have side venting and tightened the plastic y attaching to rails about a meter above the ground which were then lowered by some serious wacking with a lump hammer. Worked well if a little terrifying and hard work.

[Penninehillbilly]

penninehillbilly - interesting advice about the tensioning. Northern say they have some kind of system that allows you to move the cover up to 100mm after fixing and that allows tensioning? Maybe I need to read that again!!

It's about 25yr since we got ours, they must have developed that idea since then.

[mapahutchins]

25 years is a great advertisement penninehillbilly!!

Thanks to everyone for your comments, especially Fleecewife...so much info!!!

Ahh the hoops move...interesting, think I will have a word with my contact at Northern, see if they have decent instructions?

Your tunnel (Fleecewife) sounds similar to the layout I have been considering (in terms of crop bars and fixings etc). For the ventilation I was looking at side netting (with roll up poly) and a double door at one end (single at other). Hadn't considered the louvres but will take a look at the costs (of the upper ones anyway!).

Will definitely get the thickest cover we can afford (Northern recommended their 50/50 - neither transparent nor fully opaque...does that make sense?!).

The thing I am hearing a lot is get the ground work right or as you say if the frame isn't correctly aligned the cover will never tension.

Northern actually gave me a couple of local sites to visit with their polys installed and I have to say that both of them were very pleased with the tunnels. In fact they both had loads of advice as well and I think that one of them could turn into an interesting contact (retired teacher now into permaculture).

Starting to think that maybe I need to do a bit more research, get the groundwork sorted this fall and then get the tunnel installed next spring.

Oh, and I got a contact number for someone who is supposed to be the king of polythene tensioners...that sounds so wrong!!

Loving this smallholding thing. Everyone so helpful. Thank you all.

[Black Sheep]

One of the other bits of advice I recall was to install the cover on a hot day. On cool days it will tighten up more. If you install on a cold day it could mean you end up with a looser cover when it heats up.

[Penninehillbilly]

I agree with Black Sheep, plastic is obviously more pliable and easy to handle as well.