"Andrew Mawson" wrote
Back in February I bought my wife two 9' x 12' "Lakeland" greenhouses
as a retirement present. Due to various issues including levelling the
site etc it's only in the last month we've assembled one of them (the
other is still in bits), and within two weeks we lost seven of the
polycarbonate sheets in what I think were only light winds. I have no
faith whatsoever in the rest not blowing away soon.

The sheeting is 4mm polycarbonate twin wall that slides into channels,
and the wind makes it bow so much that it comes out of the channel.
Once out they are almost impossible to re-fit without major
dismantling. It was a seller on ebay (swiftbuys234) who reportedly
died five weeks ago so no redress there. OK our fault for not putting
them up sooner, but I believe that the basic design is flawed.

Has anyone else had this problem, or perhaps has a solution less
radical than scrapping them and starting again?

Once you have the sheets back in the channels then I would glue (silicone
type) onto the sheets something rigid like ally angle so they can't flex
again. Or for belt and braces you could drill and bolt similar both sides of
the sheets (but I'd still glue as well).

--
Regards
Bob Hobden