Windy Security!?

[Stu the fish]

Hi All - Based on a windy site - whats the best way to secure a greenhouse or polytunnel to the ground to try and give a long life for such a structure in such a position. I intend to position the unit ( Whichever I can get) short side on to the prevailing wind ( Is this right?) - Hope someone's had to do this and got some good ideas

[arthur e]

Hi Stu, Pollytunnels should ideally be positioned North/South. I live in NE Scotland And I bet your wind is not as strong as mine My tunnel is only held down by the weight of the soil backfill down the side and end as per the makers instruction and I have had no probs at all in the 5 years its been up.It's certainly frightening when your inside it during a gale and it does shake a bit, but I reckon if it can work here it will work anywhere. Mine is a Northern pollytunnel 14ftx30ft with crop bars.
Arthur

[Stu the fish]

Hi Arthur - thanks for this - I grew up on the north east coast and yep it can be windy & cold! I'm now in the south west exposed to the prevailing south westerlies up the Bristol Channel. Trust my and my fellow allotmentiers to have our plots on the only major hill in between the Somerset Levels! I've just heard horror stories from some of the old boys who have seen several sheds and green houses relocated! - thanks for your feedback

[Johnboy]

Hi Stu,
The positioning of Polytunnels should be so that the prevailing wind should flow over the polythene as in an aerofoil section.
If the prevailing wind is west to east then the length of the tunnel should be north to south.
If you do it the other way about the wind will be forever charging the tunnel and blowing-up the tunnel inflating and deflating. This ultimately shortens the life of the polythene.
I live in an area of high wind, at the head of a valley, with the prevailing wind coming from the northeast. The wind here is such that all the trees on the plot have a lean to the southwest with some up to almost 15 degrees leaning. The last time the tunnels were recovered was spring 1995 and I am expecting them to expire at any time now. The neighbouring nursery has re-covered their tunnels three times in this period and their tunnels are running with the prevailing wind whereas mine run across it.
Always choose a high quality Visqueen membrane as it eventually pays dividends. Hot-spot tape is absolutely essential.
JB.

[Stu the fish]

John boy - top man thanks very much - very useful feedback -have a great weekend - Best regards
Stu the Fish!

[richard p]

with a green house or shed the short solid side should be towards the wind, makes it harder to blow over, if a greenhouse door is into the wind and lets gusts in the air pressure inside can blow the glass off. even a strong rigid shed needs anchoring down to good heavy foundations or it will eventually blow away.

[kranser]

for a greenhouse foundations, I used 4 large metal stakes (with the top open section filled with a wooden block of the right size), 4 wooden strips which are nailed/screwed to the top of the stakes (once the stakes are buried in the ground. This forms a sturdy square wooden frame with which the greenhouse can be attached to.

Mine has survived strong winds using this method.

Kranser.

[Johnboy]

My greenhouse is on a 12" x 6" concrete foundation all round the periphery with bolts used to hold down heavy machinery set into the concrete. The bottom sections of the greenhouse aligned and predrilled and this means that the greenhouse is erected, the frame slotted onto the bolts and then the nuts are screwed onto the bolts. During the winter months I fit diagonal braces and if that manages to blow away I would be more than amazed.
With my poly-tunnels the ground tubes are set in concrete. I do not bury the polythene but instead have a wooden rail fitted to the tubes at ground level and the polythene is then fixed to the rail using wooden battens screwed to the rail trapping the polythene. Should the polythene need tightening the the job is then a very simple operation.
JB.

[Johnboy]

I omitted to say that my tunnels are commercial tunnels and because of the high wind in this area they all have three ridge poles and extra diagonal braces.
JB.

[Stu the fish]

Thanks Guys - really helpful - i'll post how I get on - along with anything I learn from the experience - aiming for a 12 x 8 timber frame polyhouse for under £100 total outlay. our 2 year old will eat that in Tom's next summer no problem!