On 03/12/2014 22:30, Michael Uplawski wrote:
Good evening,

The whole greenhouse will be 6x20m (120m²) with vertical “walls” up to
about 1.9m, which means a considerable weight, but also a considerable
surface. Even if I choose an intelligent orientation and a good
compromise between insolation and wind resistance, some additional
anchoring should be needed, I guess.

Absolutely essential I would say. Your structure will be a fair bit
heavier than a normal domestic garden greenhouse, but you really don't
want it being moved by the wind during a powerful storm.

I would also recommend replacing the cross bracing on the prevailing
wind side with a heavier gauge of aluminium angle. My 3x6m failed in the
winter storm of 1997 when the wind loading at ~100mph bent one of the
standard corner reinforcing struts which shattered a pane of glass.

Once wind got into the structure it lifted the roof and doors off. I
guess it depends how exposed you are and the intensity of the storm. It
is well worth keeping some twinwall or at a pinch plywood for quick
running winter repairs if you will be heating it for tender plants too.

http://www.nezumi.demon.co.uk/garden/gizmos/gizmos.htm

Nearby commercial glasshouses and polytunnels were also trashed.

--
Regards,
Martin Brown