Where to buy a large polytunnel?

[Annpan]

It's more a matter of this greenhouse structure having a limited lifespan - maybe 5 years - putting solid foundations down would mean more work to remove them in the future.

We are beyond that now anyway - OH has said a very firm "No", and since it is me that usually puts my foot down on things I think it is only fair to let him have this one.

Polytunnel plastic is guaranteed for 4 years (which gives us enough time to know it is for us) and can last up to 10 years - it costs about £50- £75 to replace and the old plastic can get used on cloches and other smaller things until it disintegrates. I know it isn't as good as glass, but also not as deadly.... I think glass is now out of our budget now anyway.

[Jandra]

I've succesfully grown tomato's, bell peppers and cucumbers in a small-ish polytunnel (9 x 12 ft) on my allotment. It might be a greenhouse is even more suitable, but I'm really pleased with my tunnel in that respect.
Also I'm currently eating rocket and lettuce from the tunnel, despite the fair bit of frost we've had a few weeks ago.

I use 'regular' anti-UV coated tunnel covering and it's holding up nicely (tunnel has been up for two years now). You do get some dripping and I have a insect netting covered hole (on the wind side) in one end and the door also has a strip uncovered, so that I usually have enough ventilation. In summer I keep the door open day and night. Even with constant ventilation I'm always surprised how much warmer the tunnel feels in winter than the outside temperatures. Unfortunately I don't have a good thermometer.

I'd go for the cheaper covering (I think plenty of people use it succesfully, after all) and upgrade in a few years if you find it doesn't perform to your satisfaction.

Good luck. It's great (!) to have polytunnel.

Regards, Jandra

[Odsox]

I have a "regular" uV stabilised polythene cover and it's 3 years old now and still fairly transparent ... except for a fair covering of green algae. Another plus point for a greenhouse, glass is a LOT easier to clean than polythene.
One point I would make though, ensure that you have a door at both ends for a through draft in summer, and make sure the doors are wide enough to get a wheelbarrow through ... some aren't for some reason.

[Green Aura]

Ours is also just the UV stabilised stuff. Apparently the UV protection treatment only last a couple of years anyway (don't know about the anti-fog bit) so it seems pointless to pay extra money for something that may not last. The cover we bought should stay intact for 4-5 years (maybe less up here) although some people have had there's for much longer.

[Annpan]

Thanks :D

The anti-fog stuff is supposed to stop condensation and it somehow (I don't know the physics of it) it dissipates the heat more equally and retains heat better - I was thinking that if I can keep it above 0oC that would be a huge advantage.

[Green Aura]

We've put a Strawbridge style heat sink in ours.

Dead cheap, we used a a polystyrene box that some organic meat came in, filled it with a bag of pea shingle, bought a small bore drainpipe and some angled connectors, and a solar-powered fan - less than £25 the lot!

The temperature hasn't fallen below 2oC all through the winter, thus far. And both our doors have mesh tops, rather than plastic, so there must have been some chilly winds blowing through there at times.

[Annpan]

Right.... I can't decide and it is driving me MAD!

Do I get a crop bar kit?

is 10ft or 12 ft wide a better option?

Should I get a wider but shorter one that can be extended later? or is 'later' going to be in 10 years when we have moved out? would we take it with us?

I have a budget which can easily get stuffed when I look at what I'd really like (12x30 with cropbars and double doors = £559)

Ny other pointers? I would have really liked to get it ordered this week as I am missing a lot of sunshine out there

[Odsox]

I don't have crop bars with mine and I can't say that I would get them if I were to replace my tunnel. The only use I can see for them is if you want to grow runner or French beans and I grow mine in the centre bed and use the centre roof beam.
Not sure if you have a choice but I would recommend the tunnel with vertical sides up to about 4' 0" rather than the curved ones. It restricts what you can grow in the side beds and makes working more difficult.
Width ... I have a 12' one which gives me a 4' centre bed with a 2' path either side and 2 x 2' side beds. The beds are raised (like deep beds) and can be worked from the paths.
Hope that didn't confuse you even more

[Annpan]

Just the kind of input I needed thankyou

[Green Aura]

Don't know about the size bit, but we got the crop bars. They add stability to the structure. We hung baskets off them and grew nasturtiums and other salady bits, so they were useful for that as well. We've also got the fan for the heatsink on one and the solar panel on another, so there are quite a lot of things you can do with them. We're toying with putting a grape vine in this year, which will grow between them utilising the top of the polytunnel.

So my advice would be go for the bars.

We chose width by what we could fit - 10' wide gives us 4' beds up each side with a path in the middle. Getting to the back of it can be quite difficult but with a wider one you could have shallower beds, with another bed up the middle maybe.

i wrote this as the above was being posted - sounds like a middle bed is good.

[Odsox]

but we got the crop bars. They add stability to the structure.

There you go ... just depends on what you want to do in there.
I would like to point out regarding the stability, mine without bars is certainly stable and has survived winds of 90 mph end on.
Just wouldn't want you thinking that a bar-less one is all floppity.

[ajstone]

We had three large polytunnels 29' x 120' single span 42' x 72' twin span and 14' x 70 single span.
All of them had LBS anti-fog, all of them lasted until they were cut off when we moved. The lady that bought our house didn't want them.

A few tips
If concreting in the ground tubes make sure you keep the hole to about bucket size.
Dig your trench at least a foot out from the tubes to keep the sheet away from the concrete.
Make sure there is no chance of wind on the day you choose to cover the tunnel, I have been dragged off my feet when the wind got up to a gentle breeze.
Make sure you have enough people to help you a 70' will need four people.
Lay the sheet loosely over and use the fold lines to make sure you have evenly over and not on the p***.
Fix the sheet at the top of the door ends as tight you will need to cut an open in the sheet leave it long wrap it around a batten pull it as tight you can before fixing it. Then work your way to the ends one hoop at a time either side of the center of the tunnel.
Lay the sheet in the trench back fill it a little and pull the sheet as tight as you can then stand on it in the trench
Use a fork to make drainage holes in the sheet in the bottom of the trench.
Once at the corners you will need to fold them, pull the sheet to the door opening and roll the sheet in a bayou will have a lot of excess to cut off.
When you have finished push some stakes into the trench it will help hold the sheet in high winds.

Have fun.

[MuddyWitch]

Just to confuse you further...I have a 25' by 12' tunnel & wouldn'y like to go down to the 10' size.

My crop bars are SOOOOOO useful; tie tops of canes to when growing stuff like toms, store said canes in, hang baskets & pouches from to harden off, hang bits & bobs from(like the twine ball & a pouch with my gardening gloves in so the fox can't get 'em), a scaff plank between tow acts as a plant pot shelf, I hang my MP3 from one when using the tunnel as a potting shed and in the depths of Winter or on wet Summer days I dry washing from a line stung between them.

If you can possibly afford them I'd definately say get them.

MW

[Annpan]

Thanks guys... I had been thinking a 10x 20 ft tunnel... but now I have sorted it all and on your advise....

I will be getting the 12x15 (I can always get more later) with crop bars, that almost keeps within my budget

thanks guys