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We have a large, detached double garage that we'd like to convert into a hobby room (no sleeping or toilets).
It has a corrugated metal roof on it at the moment which is in really good condition that I could reuse but it's been mentioned that it could sweat over the insulation/rafters etc and cause damp and rotting. Is there any way to stop this?
Would ventilation help?
I've seen anti-sweat paint for metal roofs. But that sounds like it could just send the moisture somewhere else 
.
I'm also looking for advice on the construction of the roof as it is 19 foot deep and 26 ft wide with a single skin brick wall diving it about a third across. Would it be acceptable to have a joist across the middle to have shorter rafters either side? Even a 9x3 doesn't cover the span according to the span tables. So I could use a 9x3 as the centre support and 7x2s in 3m lengths from front wall to the centre and then Centre to back wall. I've drawn a picture as I read that back and it doesn't make much sense .
I'm hoping it doesn't require a steel beam as it would need to be mechanically lifted and that's not an option cost wise or access wise right now.
Any advice gratefully recieved. I don't plan to go ahead with anything until I fully understand it in theory.
It has a corrugated metal roof on it at the moment which is in really good condition that I could reuse but it's been mentioned that it could sweat over the insulation/rafters etc and cause damp and rotting. Is there any way to stop this?
Would ventilation help?
I've seen anti-sweat paint for metal roofs. But that sounds like it could just send the moisture somewhere else
. I'm also looking for advice on the construction of the roof as it is 19 foot deep and 26 ft wide with a single skin brick wall diving it about a third across. Would it be acceptable to have a joist across the middle to have shorter rafters either side? Even a 9x3 doesn't cover the span according to the span tables. So I could use a 9x3 as the centre support and 7x2s in 3m lengths from front wall to the centre and then Centre to back wall. I've drawn a picture as I read that back and it doesn't make much sense .
I'm hoping it doesn't require a steel beam as it would need to be mechanically lifted and that's not an option cost wise or access wise right now.
Any advice gratefully recieved. I don't plan to go ahead with anything until I fully understand it in theory.
