I am going to close in a carport and make it a workshop. The roof framing is made of trusses with 2X4 batt strips and a tin roof with no moisture barrier beneath the tin. The carport is open on all sides and there has been no ceiling, just the exposed trusses underneath. My question is, when I close the carport in will I need to take the tin off the roof and put a moisture barrier to prevent the tin from sweating and rotting my roof framing? I forgot to mention that I live in south Louisiana (humidity capitol of the world).
Edited 11/5/2006 9:38 am ET by crowdaddy
Replies
crowdaddy.
I'll be honest i don't know.. I'm a bit north of you.. ;-) Minnesota.
Tin would be a moisture barrier if it doesn't leak.. Does it?
sure vapor will get around it but it will anyway. My gut tells me that if it doesn't leak adding a moisture barrier won't change anything.. Just give you a second line of defence against driven rain..
I reworked a roof like that in an open carport. Metal roofing over skip sheathing and it would sweat all over the owner's car. We pulled off the metal (exposed fasteners), pulled off the skip, replaced with plywood, added 100% ice and water shield (very low slope), and reinstalled the metal. That solved it.
you mean you still have a roof!
David,
I don't have a problem now with the sweating I'm just afraid that when I put the ceiling underneath and slow the air circulation that I may start one. Even if I don't have condensation dripping on the ceiling I may have mold and mildew problems. I think I am going to take your advice. What is a 100% ice and water barrier? Down here we typically just use 30# felt as a moisture barrier.
Here's the Grace website and some info on Ice and Water Shield.
http://www.graceathome.com/pages/roofing.htm
It's a heavy, adhesive-back membrane that we used because the carport roof was very low slope, maybe 1:12. If you have 3:12 or steeper you could go with felt. For that matter on a lower slope you could probably go with 50% overlap on every course and use felt. I&WS is an expensive product and is a life-saver in a lot of situations. I can't remember but I think I pay around $175 per roll.