cwr Posted January 3, 2020 Share Posted January 3, 2020 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. Link to comment Share on other sites More sharing options...
scottishjohn Posted January 3, 2020 Share Posted January 3, 2020 17 minutes ago, cwr said: How best to avoid condensation on the inside? spray inside with closed cell foam Link to comment Share on other sites More sharing options...
Ian Posted January 3, 2020 Share Posted January 3, 2020 @cwr you can buy profiled metal roof sheeting which has a thin anti-condensation fleece pre bonded to the underside. Link to comment Share on other sites More sharing options...
cwr Posted January 3, 2020 Author Share Posted January 3, 2020 Ok. And then seal the edges at the wall plate so there's no ventilation? These sound like gd options to price up. Link to comment Share on other sites More sharing options...
joe90 Posted January 3, 2020 Share Posted January 3, 2020 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. Link to comment Share on other sites More sharing options...
Ian Posted January 3, 2020 Share Posted January 3, 2020 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. Link to comment Share on other sites More sharing options...
cwr Posted January 7, 2020 Author Share Posted January 7, 2020 Ok thanks, I'll price up the spray foam. So any recommendations on purlin size, 5m span, 1m pitch. Link to comment Share on other sites More sharing options...
Simplysimon Posted January 7, 2020 Share Posted January 7, 2020 alternative would be to use corrugated cement fibre roof, no drips and quieter when it rains Link to comment Share on other sites More sharing options...
Cpd Posted January 7, 2020 Share Posted January 7, 2020 1 hour ago, Simplysimon said: alternative would be to use corrugated cement fibre roof, no drips and quieter when it rains Do they do it with a curve ? Link to comment Share on other sites More sharing options...
Simplysimon Posted January 7, 2020 Share Posted January 7, 2020 apparently.... 1 Link to comment Share on other sites More sharing options...
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