This Wednesday the Pole Barn Guru answers reader questions about the need for a vapor barrier, the longevity of properly treated posts, and the better spray foam between open and closed cell.
DEAR POLE BARN GURU: Hello Sir, hoping you can help answer a question I cannot get a straight answer on. Currently building a 30x40x14 building and have the walls and roof house wrapped with Kelly Clark Block It. Steel is going on the building now. I just ordered steel for interior ceiling and trying to figure out if I should add a vapor barrier to bottom of truss first. Thoughts? MATT in ILLINOIS
DEAR MATT: Block it is wrong product for under roof steel. It allows moisture to pass through and be trapped between it and roof steel. As long as you do not blow in cellulose, you should not need a ceiling vapor barrier.
DEAR POLE BARN GURU: I bought a pole barn that has been retrofitted to a house. The posts are in ground. I’m worried about future resell and longevity of the post. Also, I’m in a cold climate and wonder if a proper footing would help with heating. Is there any good way to retrofit from in ground post to stem wall or something similar. I’m sure it’s all possible if money was not an issue. I’m looking for an economical solution. Thanks!! NICK in WEST LIBERTY
DEAR NICK: Properly pressure preservative treated columns (UC-4B) should outlast anyone alive on our planet today, especially in climates (such as yours) not prone to termite infestations. As for improving ability to heat – dig a trench around outside of building at least two feet wide and two feet deep. Invest in 2′ x 8′ (or 4′ x 8′ to be cut in half lengthwise), R-10 EPS insulation boards. Attach vertically to exterior side of pressure treated splash plank with top of insulation even with top of interior concrete slab. Run another 2′ horizontally out away from building at bottom of vertical. Any portion of vertical insulation above backfill will need to be protected from UV rays. This should keep your slab from getting so cold, as well as help to avoid frost heave. If you are in an area prone to burrowing rodents, you should further protect insulation https://www.hansenpolebuildings.com/2021/03/rascally-rodents/
DEAR POLE BARN GURU: I am trying to decide whether to go with open cell or closed cell spray foam on my bare metal pole barn walls. I will be enclosing the walls with some material, most likely plywood. What are your opinions regarding the pros/cons (is one or the other worse for corrosion, condensation, other pertinent factors, etc.) of the two foam approaches? Thanks so much! TERRI in CHESTER
DEAR TERRI: Open cell spray foam allows moisture to pass through and condense against steel cladding. I would not recommend it being used unless a two-inch thick layer of closed cell was first applied, then add open cell for extra R value (and to deaden sound).
DEAR JASON: If yours is typical post frame (pole) building construction, your opening probably measures 12 feet from center of column to center of column, in which case you would be looking at needing a 12 foot width split sliding door. This would give you two door leafs just over six feet in width, enough to cover the opening, provide an overlap on each side and be able to be covered with two three foot widths of steel siding.
DEAR TIM: Thank you for your kind words, I hope to be both entertaining and informative. Will painting the entirety of the buried portion of a treated pole in roofing tar help preserve the wood? Well, it might, although I have found no studies which would confirm the ability. I did find an interesting article in Scientific American, which may shoot down the idea: 
DEAR ABE: Do not use this insulation as you have intended, it will cause you nothing but grief. Not only will your post frame barn roof leak, but the diaphragm strength of your roof steel will be severely compromised, which could lead to a catastrophic failure. Tyvek and other building wraps are not condensation control barriers, they are moisture barriers. There are several possibilities – invest in roof steel with Condenstop or Dripstop preapplied, use a radiant reflective barrier between the purlins and roofing, or spray closed cell foam on after the roof is installed.
The skids of steel with Drip Stop applied must be stored prior to use, to prevent moisture from becoming trapped between panels, which may cause staining as well as damage to the panels. This moisture can originate from a variety of sources, such as rain, high humidity or condensation. Panels should be stored in a dry location and installed as quickly as possible after delivery. If this is not possible, panels should be separated from one another to allow for air circulation to prevent panel damage.
