This Wednesday the Pole Barn Guru answers reader questions about a home owner asking builder to install housewrap on the roof, the best solution to insulate underside of roof, and what the best fastener for screwing steel to ceiling or roof trusses would be.
DEAR POLE BARN GURU: Pole Barn Guru, thank you for your knowledge. I have a customer wanting house wrap around the exterior of a 30×40 pole barn. Is house wrap to be installed in between purlins and roof steel or will I need a radiant barrier to prevent condensation? Home owner says house wrap on the roof as well but I’m not sure if that’s the route he really wants to go. House wrap on side walls in between girts and side steel is also the best route correct?
Thank you for your kind words, they are much appreciated. Provided your client will not be doing closed cell spray foam on walls, use house wrap between girts and wall steel. For his roof, housewrap is totally incorrect, as it allows moisture to pass through and become trapped between wrap and roof steel – potentially causing premature degradation. If your client is not closed cell spray foaming directly to roof steel, then order your roof metal with an Integral Condensation Control factory applied (Dripstop, Condenstop or similar) https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/. If roof steel has already been ordered (again assuming no closed cell spray foam being applied), then you do need some sort of a thermal break – such as a well-sealed radiant barrier.
DEAR POLE BARN GURU: Hi Mike, I built a 32’X40’X12′ pole building, (Shop) I used 1 1/2″ foam board on the inside walls, (on the inside of the girts) I can’t decide how I should insulate the underside of the roof. I have had a couple Spray Foam guy’s quote it , that’s pricy. Of course, the best R Value etc. at the most reasonable price is what I am looking for. In some of your post you have mentioned Rockwool that has gotten my attention. I see they make it up to R30. One thing that sticks in my mind is, my builder suggested not to use an insulation that will give insects a place to live. What would be your suggestion for underside of Roof insulation. Thank you. JIM in SPRING HILL
DEAR JIM: If your building has no current provision for controlling condensation on underside of roof steel, then two inches of closed cell spray foam applied directly to steel is your best insulation option. If you desire a greater R value, you can go thicker, or add open cell.
DEAR POLE BARN GURU: What screw is best for installing metal panels on the ceiling to wood trusses. MICHAEL in WENTZVILLE
DEAR MICHAEL: Most people are using #9 or #10 diameter 1″ screws. If you have ceiling framing 24 inches on center and want to utilize strength of ceiling liner panels to help transfer wind shear loads, then 1-1/2″ long diaphragm screws would be a better design solution.