Allotments 4 All
Produce => Under Glass => Topic started by: Vinlander on November 10, 2009, 23:15:10
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Corrugated PVC seems to be a good material except that my attempts to roof a shed have been extremely disappointing.
I may have skimped slightly on supporting it but I'm not convinced that explains why it started to split after only 2 years.
On the other hand nobody else seems to have any problems.
The only thing I can think of is that the ventilation of my shed can make the roof bow outwards - which might exaggerate any cracks in the outer surface.
Has anyone else a clearer picture of what makes this material perform well or badly?
Many Thanks.
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the corrugated pvc sheeting seems prone to UV decay, becoming brittle in 2 - 3 yrs. (it's not just you)
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Thanks Tonybloke - sounds like rigid structures with lots of fixings are the answer.
I've definitely had UV failure with perspex covers over wall peaches - but it was much slower - more like 5 years+ and it was obvious that if I'd maintained the surrounds better they would have lasted another 5 years (judging by the state of the broken bits now - still fairly strong and only slightly brittle 3 years later).
I tend to skimp on woodwork and I'm a bit loose on maintenance so it's probably a good thing that I'm now a firm believer in polycarbonate.
However I've noticed some cacti don't do well under PC - mainly desert kinds and those climbers that can reach the tropical sun (my epi-cacti seem happy but they live under trees in Costa Rica) - I'm wondering if PCs natural UV resistance means it doesn't let much UV through...
Cheers.
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It is important to have adequate and frequent support and fixing to prevent excessive flexing of the roofing in the wind, which can lead to fatigue cracking of the material. Wind flowing over a roof can cause very high suction forces, leading to the frequent reversal of stresses. As an Engineer, I once had to investigate and report on the cracking and failure of roofing materials on new industrial sheds, which was caused by the same effect.
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Thanks Realfood,
I think this means that:
1) I'm saving much more money by only making moderately sturdy structures than I'm spending by using polycarbonate.
2) Not to mention the much reduced maintenance.
3) And the fact that after 20-30 years when it's too yellow to use as a roof it remains a good durable rot-proof panel for building sheds - even raised beds etc.
I did get a small hole in my 20 year old cover when a brick dropped off my neighbour's roof - but I'm not sure even a new panel would have coped with 2.5 sharp kilos moving at 20mph.
Cheers
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stopped using corrugated years ago.
why not try this
(http://i475.photobucket.com/albums/rr111/gardentg44/allotmentphotos076.jpg)
monarflex now 6 years old still good as new
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Is that monarflex a tarpaulin? It looks a lot like what I've got on my polytunnel.
If so how do you stop it booming in and out when the wind changes?
Or is it some sort of ultra-stiff super-tarp?
Cheers
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[Is that monarflex a tarpaulin? It looks a lot like what I've got on my polytunnel.
If so how do you stop it booming in and out when the wind changes?
Or is it some sort of ultra-stiff super-tarp?]
Cheers
monarflex or power clad is a sheeting used on the outside of scaffolding.
its very strong.
its interwoven in tiny nylon squares and does not tear.
the roof rails on mine are spaced 15 inch apart,which seems to be quite sufficient.
i think it will last another 5 years at least.
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Can I just ask, which monarflex do you use - is it the lightweight one (with 12mm x 12mm grid)?
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[Can I just ask, which monarflex do you use - is it the lightweight one (with 12mm x 12mm grid)?]
yes. around £50 for a 50mtr roll
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[Can I just ask, which monarflex do you use - is it the lightweight one (with 12mm x 12mm grid)?]
yes. around £50 for a 50mtr roll
Wow - how wide is the roll?
The cheapest I could find for any clear ripstop tarp has been about £1 per sq metre - and I kind of doubt your roll was only 1m wide! (not much use as a tarp).
I'd love to know where you bought it - do a personal message if you prefer.
Cheers.
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Try Ebay. I used this on my poly greenhouse on GTG's recommendation, been very impressed with it so far.
2m x 45/50m seems the most common size.
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Just bought some of this from scaffolding direct. 2mtrs x 45mtrs. £63 including delivery. Good stuff. Going to use it to keep the cabbage whites off.
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That's very cheap and would make a fantastically durable cloche! Or my favourite wall peach cover (a quarter ellipse shape). It's always a lot better to use a curved frame for anything that isn't really stiff.
I looked on the website and they also do a 3m wide version - if I could work out a way to join 2 bits to make 6m wide I'd have four better polytunnel covers for not much more than twice the cost of the last one I bought...
It would be worth trying to weld it (through paper) with a hot iron like I used to make sails when I was a kid (maybe sew it first with dental floss or string).
Many thanks for the update.
Cheers.
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I looked on the website and they also do a 3m wide version - if I could work out a way to join 2 bits to make 6m wide I'd have four better polytunnel covers for not much more than twice the cost of the last one I bought...
I was thinking the same when I was watching the battering the tunnel has taken the last week or so (so far so good).
I'm also thinking of using it for the planned shed roof - plus side would be that I wouldn't need to fit windows, but the insulation properties would be less than wood/ felt.
And this is before I've even got hold of any! ;D
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And.... gardentg44 - how do you attach it to the structure as in the photo? Do you batten it down or staple it (staple gun or bigger staples?)?