Tag Archives: insulating a ceiling

Dear Pole Barn Guru: Do I Need Vapor Barrier?

Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays.  With many questions to answer, please be patient to watch for yours to come up on a future Monday or Saturday segment.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com


DEAR POLE BARN GURU: Builder just built a pole barn, 36x53x11.  Great looking.  I was planning on finishing the ceiling and insulating it.  Because of this he left out the vapor barrier, said you don’t need that If you are insulating the ceiling?


 DEAR PERPLEXED: I will assume you have a steel roof. If so, your builder has done you a huge disservice by not using a vapor barrier. Why builders so often do this is beyond my comprehension.

In all probability you are going to experience condensation problems. Before you get the ceiling in, you are going to have dripping from the underside of the roof steel onto the floor, usually at every purlin.  Once the ceiling is installed, prepare for damp insulation (reducing its efficiency), as well as mold forming within the attic space. Not a pretty sight and eventually the decay could cause failures in the roof members.

From where you are at now your best, albeit not inexpensive, solution is going to be to spray foam the underside of the roof steel. You also need to provide adequate ventilation to the attic space you will be creating. If you have enclosed vented soffits on each sidewall and a vented ridge it should prove adequate. If neither of these are present, you can add gable vents. Each end would need a minimum of 3.18 square feet on net free area, with the vent placed in the upper one-half of the attic.
DEAR POLE BARN GURU:Will roof trussing work on 6 foot center for a 30 by 60 hay barn with 2 by 4 purlins? VASCILLATING IN VIRGINIA                 

DEAR VASCILLATING: Trusses – certainly they will work spaced one every six feet, however unless you are willing to place sidewall columns every six feet, it will necessitate having headers (truss carriers) between the columns. On the purlins, depending upon your snow load and grade of available lumber, you might need to place the purlins on edge. It is very probably your idea is not the most cost effective design solution. I would encourage you to investigate sidewall columns placed every 12 feet, with double trusses at each interior column and 2×6 purlins or larger joist hung on edge between the trusses. This is going to be the best design solution structurally and is almost always the most cost effective.

Today In: Ask the Pole Barn Guru

I recently got this email, and as The Pole Barn Guru, I am happy to respond to building questions which are not from Hansen Building clients, either prior or future.



I live in Indiana.

I have a pole barn garage. I didn’t build it. It was built when I got the house. It has a metal drop ceiling. I am looking to insulate it. It will only be heated when I am working on stuff in the winter and not all the time. It will not be conditioned in the summer. I am not sure what the best way to insulate above the drop ceiling. Can I use blow in insulation? If I go this route do I need to put plastic down on top of the metal first then blow it in? I am using 1 inch Styrofoam board in the walls board since I can put it directly against the metal and moisture won’t affect it. I will eventually cover it with plywood. What should I do for the drop ceiling?”

The initial step is to find out what the load capacity of the trusses is. Very few pole buildings have trusses which are designed to support the weight of a ceiling and insulation. You should be looking for a minimum bottom chord dead load of five psf (pounds per square foot). If the prior owner did not provide you with the information about the building, the design loads are supposed to be stamped on the trusses.

Assuming the trusses can support the load, an insulated vapor barrier must be placed beneath any roof steel. If the building was not originally constructed with one, reflective radiant barrier (aluminum side up/white face down) can be added to the underside of the roof purlins. It is essential to have all seams tightly sealed. See www.buyreflectiveinsulation.com to calculate needed quantity and price.

Ventilation must be provided for, as you have a dead attic space. Hopefully the eaves have enclosed vented soffits – to provide an air intake. Along with this – a vented ridge is required, in order to give an outlet.

Finally, once all the above have been taken care of, insulation can be blown in directly above the steel ceiling liner panels. You do not want to have a vapor barrier directly above the existing ceiling, as it could allow moisture to collect above the liner panels and this could cause premature deterioration.

Do you have a burning building question (no pun intended) for The Pole Barn Guru?  Email me today!