Today’s Ask the Pole Barn Guru discusses reader questions about an option to layer insulation between purlins, the actual building width for 36′ trusses, and the recommendation against the use pit material when performing site prep.
DEAR POLE BARN GURU: Hi, I have the traditional roll type insulation with the white backing. My question is if I’m able to add more insulation between the purlins on top of the existing insulation for added r value and what type would you recommend if so? Thanks OWEN in VIVIAN
DEAR OWEN: Metal Building Insulation (MBI) is not my favorite design solution for post frame insulation (read more here: https://www.hansenpolebuildings.com/2011/11/metal-building-insulation/).
You can add more insulation to interior of what you have, without having to perforate white vinyl of you MBI. I would recommend adding unfaced Rockwool, as it is not affected by moisture and has a relatively high R value per inch of thickness compared to fiberglass or cellulose. Do not add another interior vapor barrier, as this would allow for moisture to become trapped between two vapor barriers.
DEAR POLE BARN GURU: You really are a wealth of knowledge. I’ve been watching your Youtube videos as well, very helpful.
I’m intrigued by your pole barn kits, and I had just one more question about raised heel trusses:
It’s my understanding that post spans are actually building widths minus 3 inches. So for a 36 foot building, the span between posts is 35’ 9”, correct? If that’s the case, are raised heel truss lengths in this example also 35’ 9 to the edge of the post? Or the full 36’, with the eave skirt board resting under the additional 1.5 inches of the bottom chord length?
Thanks again for your time!!! MATT in CHENEY
DEAR MATT: Our buildings (as are most Pacific Northwest Buildings) measure 36 feet from outside of column to outside of column. This allows for 12 sheets of steel plus the lap on the 12th piece (covering 36′ 1-1/2″ roughly) to be installed without having to rip the last steel panel lengthwise. Pressure preservative treated splash planks, headers, etc. will be applied to exterior faces of columns, giving a framed finished width of 36’3″.
DEAR POLE BARN GURU: Hi. In your building manual it notes not to use pit material on the building pad. If the site is leveled, I’m not sure what the function of any modified is or why no pit material in specific. We’ll be doing a slab at some point and common practice would be to put down some clean 3/4″ so if it’s beneficial to have stone on the building pad would it be more cost efficient to just put the clean stone down to start with? Thanks. KEVIN in WEST CALN
DEAR KEVIN: #1 reason to not use pit run is it is difficult to auger holes through.
#2 because it is round, it does not compact well
#3 It creates voids allowing for free flow of liquid water beneath slab
You do want to allow for two to six inches of clean sand or sandy gravel compacted immediately below your under slab vapor barrier.
DEAR KIMBERLY: No you do not have to add OSB and a Weather Resistant Barrier to your exterior walls.
Now, I’ve been told to do closed cell insulation on my walls 1” thick. I wanted an opinion on whether to go every inch of the walls top to bottom all the way to the roof? Would I benefit from the insulation at all by just going to the 10’ mark (my lowest wall height) because that’s as high as my interior osb is going anyway. I guess what I am asking is it any benefit to insulate closed cell up to 10’ mark from the floor and then just bubble foil the main shop above 10’ to give a finished look? THOMAS in PLEASANT HILL
DEAR POLE BARN GURU: We are looking to build a 40×90 pole barn, with 1/3rd being used for storage and 2/3rds for a vehicle maintenance. Both will be heated and storage cooled. Concrete floor, shingled roof, insulated, vertical metal siding, no windows, 5 overhead doors on the same side. Can you span the trusses from wall to wall and provide the above with no center columns? Thank you, ROD in CLEVELAND
DEAR CRAIG: While Building Codes do not require one – if it is absent you are likely to have periods (especially in Spring and Fall) where it will rain inside of your building. Most people erect new buildings with an idea of protecting contents from climactic conditions such as rain, so this result may be less than desirable.
DEAR POLE BARN GURU: 
