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Curved corrugated roof ventilation and purlins


cwr

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Hi folks

 

Planning ahead my garage which will have a curved corrugated roof, but wondering about a couple of aspects.

Below is the concept, purlins at approx 1m pitch, with a 5m span.

 

1. How best to avoid condensation on the inside? A membrane could be installed under the corrugated sheeting, above the purlins, though presumably a sarking board would be needed to stop it sagging between pulins causing water to get trapped? Is a vent at the top possible/necessary?

2.Any suggestions purlin sizes?

 

Thanks.

Curved corug roof.JPG

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3 hours ago, Ian said:

you can buy profiled metal roof sheeting which has a thin anti-condensation fleece pre bonded to the underside.

 

1 minute ago, cwr said:

Ok. And then seal the edges at the wall plate so there's no ventilation?

These sound like gd options to price up.


no, I bought metal roofing for my garage workshop and asked about the fleece covered stuff to avoid condensation on my tools etc and was told by the supplier it’s only any good in any well ventilated areas, cow sheds etc. You need the ventilation to dry the fleece, if not it keeps saturating then drips. My roof was not curved but I simply used  under felt to catch drips and route them to the gutter, works very well. I reckon @scottishjohn is right for your situation, spray foam.

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1 hour ago, cwr said:

Ok. And then seal the edges at the wall plate so there's no ventilation?

These sound like gd options to price up.

No, as @joe90 said, you'll need good cross ventilation from eaves to eaves. That shouldn't be a problem if you are not heating the garage. If you are worried about keeping the wildlife out you can install insect mesh at the eaves.

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