Polytunnel Choices

[Geoff]

I did my three visits last Thursday and was quite impressed with all the structures, I have no experience of tunnels and haven't been to look at any in use. I was left with a few questions and points to tidy up so I emailed all three simultaneously on Friday and quickly got to firm quotations from Premier and First Tunnels to go with what I already had from Citadel, Northern Polytunnels still haven't responded.
I decided the extra straight sides of the Citadel weren't significant, it used concreted in hoops and a few other bits and pieces made me remove it from the list. That left me choosing between the slightly cheaper (and with bigger hoops) 15% off Premier with DIY sliding doors and First tunnels where I could select their sliding doors. FT are running a 10% off promotion and have a price match promise so I pointed out Premier were cheaper and they upped the discount to 15% and got the order. As I intend to build it during the Winter which is not ideal for cover tensioning I also splashed out on the Aluminium Base Rails, which are easier to adjust, as well as sliding doors.
I ordered it Tuesday and got this today "Thank you for your order which has been despatched via Nightfreight today on a next working day delivery service" - so tomorrow looks like being exciting!
So far I have ripped up the concrete path that will be in the way, dug out the footings for the new path and smashed the old one up as foundations for it. But now everything is frozen solid. I'll post some progress (I hope) photographs to show how I get on but it is going to be a bit messy as that area is full of Winter root vegetables, might have to move them to storage.

[Westi]

I'd so much like to see your finished project - unfortunately can't afford a polytunnel but definately on my wish list! Good Luck! If any extra cash comes in I will be re-reading your post!

Westi

[sally wright]

Dear Geoff,
some tips for building.

Use copper grease on all screws, nuts and bolts. This will help them to be adjusted and/or removed in the future. This is useful when the time comes for reskinning. Aluminium nuts and bolts cannot be undone as easily as steel ones if they have seized together. They often break first.

Buy extra anti-hotspot tape and use it on any part of the structure that comes in contact with the plastic. An extra strip on the end hoops to cover "top and side". The top centre pole should be taped on top to prevent chafe when there is snow or very high winds. The diagonal braces should also be done as should any nuts and bolts that might be in contact with the plastic.

Polytunnel repair tape should also be purchased now so that you have it and don't have to let a small hole become a big problem because you cannot get to the garden centre.

Have a lot of people available when you put the sheet on. It is a lot more awkward than you might think.

Once you have the sheet on and fastened down, leave it for a few days before tightening it fully as the plastic will stretch quite a bit. I would also go over it again on a nice spring day when the plastic is warm and flexible. The tighter you can get the plastic the better as loose plastic will rub against the frame more.

The plastic skin often gives way at the tops of the end hoops as this is where the most pressure and friction occur. It might be worthwhile putting repair tape over this area in the spring to reinforce the plastic here before a problem occurs and whilst the plastic is still in good condition and clean.

If you have a choice on how to cover the doors put netting on. Then make yourself some plastic coated panels to insert into the doors for the winter. Use drop hinges on them if you can for ease of use. Don't forget to make sure the plastic faces the same way as the poytunnel skin as the UV coating is only on one side.

Make sure that you can lock the polytunnel, not so much to prevent theft but to keep the doors shut during adverse weather. There is nothing worse that lying in bed thinking is that banging noise the polytunnel door!Also if the doors open inward put a bit of repair tape where the top corner of the door hits the plastic.

That's all the things I can think of for now, have fun and dont forget to make sure the hoops are in square as NOTHING will fit properly if you don't!
Regards Sally Wright.

[oldherbaceous]

Morning Geoff, good luck with the project, and looking forward to seeing your updates.

[Geoff]

Thanks for all that Sally. I'll try and work out how much tape they have provided then think about some more. I think some clear tape I have that I use on bubble wrap and cloches is repair tape but I'll check. Would it help over the hot spot tape before the cover on the end hoops?
I use Correx panels as greenhouse insulation, I was thinking of net doors with Correx inserts (they all slide by the way, single at the bottom double at the top).
Where do you stand on netting the doorways when they are open for ventilation? I'm pretty sure I've got to stop walk in problems like dogs and cats but do I keep out butterflies or even carrot flies and risk losing pollinators?

PS : Christmas came early.

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[Gerry]

Congratulations Geoff. I'm sure you will have many happy, and productive, hours in it.

One thing which I wished I had done, was secure the ends around the door openings and the end base rail with screws, because when all was finished I needed to undo the ends to improve the tension there.

The temperature in my tunnel reached 25c today without the mesh sides being covered. But it was down to -2c during the night.

Regards, Gerry.

[Geoff]

Interesting, I had thought of doing all the battens with stainless steel screws but I've never read it anywhere. Although they are expensive I now rarely use anything else outside, for example, I screw the carrot cage together every year and then easily take it apart again. The wonders of Screwfix.
I hope the cover doesn't smell, stored in the bedroom (keeps the dream alive).

[Colin Miles]

All very interesting and informative. And Sally, you have convinced me that if I do get one it is definitely a summer task putting it up. Too wet and too much hassle here otherwise.

[sally wright]

Dear Geoff,
do not put repair tape over hot spot tape. The hot spot tape is there to reflect heat away from the metal bits AND provide a smooth slippery surface for the plastic to move independently of the frame to reduce friction between the two surfaces.
Re the use of screws I would agree with this and if you can get them and they are suitable for the task I would get the ones with hex heads that fit into sockets as they will be a lot easier to do and undo.

I would net individually the carrots to keep out the fly as it will get too hot in there in the summer if you do not. It might be worth making batten doors to open inwards with chicken wire(2" holes) to keep out cats etc that will not keep out the bees etc. If you are growing brassicas in the tunnel and wish to keep out the butterflies then go down to 1/2" mesh such as pond netting.

I should have mentioned that if you wish to have power or water in the tunnel then put in the pipework etc before you start.

Also if you are going to have hanging brackets for training wires, fleece, irrigation pipes or lights etc fitted then they are best put in as the poles go together so the hot spot tape can cover the backs of the brackets. I would put in lots as they are easy to fit now and you newer know to that use they might be put. The hotspot tape will hold most of them in place as the tunnel is erected.

Regards Sally Wright.

[Redfox]

Looking forward to seeing your new polytunnel up. I found Sally's info very interesting, it has brought to mind a lot of things that you don't think of initially. I would also love a tunnel but as we are moving to new climes in a couple of years it is not financially viable for us to buy one yet.

[Geoff]

As progress looks like being non-existent for the next few days with a combination of weather and some strange festivities (I did suggest a polythene party on the 26th but it was vetoed) I thought I would post an update. I've completed the steelwork (all with copper slip) and started the door frame at one end. I did much of the work when it was frozen by sheeting over the edges so I could dig the hoop holes but when it thawed and rained it became the mud bath you can see. The two pieces each side of the door frame are level so you can see the side to side slope problem I have - 15" at the top, 20" at the bottom - accommodated by extra long ground tubes. Current plan is to do some block work and bring the cover down lower on the right than the left. I'm going to install a water supply (with a parallel pipe that I can pull cable through if I decide to add electricity). I was amused by how the suppliers packaged the pipe and the fittings so I photographed it. I have bought extra anti-hot spot tape so I can put two pieces on the end hoops. I have bought crop bars so I can fix slate battens on them longitudinally then tension wires across the width to give me loads of support options.

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[Gerry]

Congratulations Geoff. That is looking very good. Will you be able to resist fitting the cover before the warm weather arrives?
Regards, Gerry.

[oldherbaceous]

Morning Geoff, you are getting on well, it also sits in that position very well.

Keep up the good work.

[Colin Miles]

Hi Geoff. Well done in this weather. Is it my eyes or the angle that you have taken it, but is it on a slope?

[Geoff]

Thanks for those. As well as the widthways problem described it also falls about 3' down the length.