Polytunnel or Polycarb greenhouse on windy plot...?

[polc1410]

Ohh, good point though polc. I hadn't considered that those reinforcing beams would take a fair degree of weight with snow & the thrashing of the rain. I guess if i made them from thicker wood then they could double up to hold any training wires for fruit in the tunnel? Provided the fruit isn't too heavy, as then i'd still have the same prob.

And I think - based on how it looked when split - he had built it with the 2" face being vertical. Assume he'd have had twice the load bearing power if he'd rotated it so the 4" was vertical as the load would have been through the 4" direction. Not sure the loads from the tubes would have made any difference which way it was rotated.

Not sure how much force the rain causes on the structure. Its the cheap plastic that suffers as the little clear squares are weaker than the surrounding green mesh. Snow is remarkably heavy - people die in avalanches with only a couple of feet of snow above them because its to hard to dig yourself out. You'll see even the fruit cages say to remove the top net cover in winter because of the weight of snow! Most years I doubt the couple of inches of snow we get would make much difference and down your way thats probably as bad as it gets. Up here we've had close to a foot of snow for a week at a time at least twice in the last 2 years.

I guess the fruit will be present during summer when you'd hope snow will be less?

Plotman's price seems much cheaper than I was expecting. (Company called firsttunnels on ebay seems to have that kind of price).

They also sell domestic tunnels (look a bit light weight to me) but for one the size of my greenhouse with a door its nearly 3 times the price, I'm guessing by the time I've paid for all my silicone and extra clips etc twice the price. I suspect that doesn't scale though so if you want twice the size of my greenhouse its probably similar cost.

Other thing to think about would be ventilation. Most polytunnels don't have windows you can open (just a door). I've seen people customise the door to include a window. You might want to look at your options with that. My greenhouse will have an auto-opener on one of the windows to stop it over heating, presume you can do something similar in a poly.

Final thing is a single film poly in winter wont keep the heat as well. It'll be a darn sight better than nothing or a blow away, but not as good as a solid glass construction with extra insulation layers added etc. Not sure how easily you could add bubble wrap to the inside of a tunnel for instance. So you need to think about your crop over winter...