Need for an underlayment on metal shed roof
I’m a longtime lurker of this forum. I’m building a simple 10×12 gable shed here in rainy Seattle area. Roof pitch is 10:12. It has 12×12 inch gable vents at both ends. The shed will be unconditioned/no insulation. Was planning on 1×4 skip sheathing with a metal roof to match our house and no waterproof or water resistant barrier. A contractor friend noted that metal roofs can often have condensation form on the underside when the inside temp is warmer than the outside (e.g. early evening on what was a hot, humid summer day). I’ve heard and read different opinions on this, but I trust the advice on this forum more than others. It’s just a shed, but I want to do it right and not have water issues so I’m thinking the waterproof/water resistant barrier would be wise. What would you all recommend? And if you recommend a barrier of some kind, should it be waterproof or water resistant? (I’ve heard that Grace Tri Flex is good…) Many thanks.
Replies
We use any kind of synthetic paper run perpendicular to the purlins. It’s enough to keep the condensation at bay. A better option is to sheath with plywood and run the paper perpendicular to the metal sheets. It’s a better install and usually cheaper than skip sheathing.
I would install Zip sheathing, tape the seams and never worry about it again.