On Nov 30, 5:47*pm, "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 4mm is a bit weak, but you should be able to attach it so that it
will not blow away. Even the 10mm twinwall will bend and spring out of
clips and sealant in 90+mph winds. I know by experience.

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.

Simplest solution is a spar of wood behind the middle of the sheets
(doesn't need to be very wide) and drill small holes in the centre of
each pane (or if you are paranoid 2 holes 1/3 and 2/3 the way across.
Then use a screw with a decent sized washer to spread the load into
the wood. The panels cannot then jump out. You may want to coat the
edges with bath sealant to stop drafts while you are at it.

I use 4mm grade on the opening lights on my greenhouse. It is much
less likely to be destroyed if the wind manages to snatch the
thermostatic opening vent and snap it back hard.

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

Polycarbonate jumping out - yes even with the really heavy grade and
nominally matching clips. Sealant helps but after a while the flexing
breaks the seal and then you still get them going in very strong
winds. I have not lost any that were screwed down and a keep a piece
with a baton and two bolts attached permanently for running storm
repairs.

Regards,
Martin Brown