Reader JUSTIN in MONROE writes:
“Hello. Hopefully an easily answered question? I have built a 52×30 post frame, steel siding and roof. Walls have Tyvek between steel and girts. Roof is steel directly on purlins with no barrier of any kind. It has a concrete slab and I plan to periodically heat it during winter months. I’d like to insulate but not sure of best method with my situation and climate. I plan to use R-19 for walls and possibly ceiling. Or blow in for ceiling. Also I have 50% soffit ventilation with 18″ overhang as well as 40 ft of ridge vent. Should I use poly plastic on interior of walls and ceiling? I’m concerned I will create a moisture problem. I’m open to doing things whichever way is best. Things are always easier and cheaper to do it correctly the first time. Any advice would be greatly appreciated. Thanks”
Dear Justin,
I agree things are always best when done correctly the first time around. While it is not always less of an investment, when the long term problems arise and things have to be corrected, it makes it nearly not as fun and cheap becomes expensive. Usually in a quick hurry.
If the roof trusses are not designed for at least a five pounds per square foot bottom chord dead load, you are sunk on adding a ceiling without an engineered truss repair. This would be the place to start, as it will dictate the solution.
I will approach the building as if it is my own and from where it is now.
On the floor – I am hoping you have a vapor barrier beneath the concrete slab. If not, use a high quality sealer on top of the floor.
A penetrating concrete floor sealer is likely the best bet to protect and maintain a concrete floor. These concrete floor sealers penetrate deep into the concrete’s pores coming into contact with the alkali and calcium ions, forming a gel.
This gel expands filling the pores and hairline cracks inside the concrete, turning the concrete into a solid mass. This process will prevent moisture and vapor migration up through the concrete floor, as well as down into it.
Look for a penetrating concrete floor sealer which is water based and says silicate penetrating solution on the specifications. These sealers can be applied with a pump up sprayer.
On the Walls-you did good with the Tyvek. Kudos! If your building has girts flat on the outside of the columns, you can add another set to the inside of the columns. If you have 6×6 columns, your post frame building will now have an 8.5 inches thick insulation cavity. I would use BIBs (read about BIBs here: https://www.hansenpolebuildings.com/2011/11/bibs/) for my wall insulation, and would have a deep enough cavity to get around R-35. There does need to be a vapor barrier on the inside (heated) side of the wall, under the gypsum wallboard.
Roof– the underside of the roof steel needs to be isolated from any warm moist air which would enter the attic. Use closed cell spray foam directly sprayed directly onto the underside of the roof steel. Assuming your building’s roof trusses are strong enough to support a ceiling, blown in insulation is going to be your most economical. Hopefully you (or your builder) had the foresight to order roof trusses with a raised heel so the insulation will remain full thickness from wall to wall. If not you may want to have closed cell spray foam insulation on the “cold” side of the ceiling in the area with a couple of feet from the sidewalls. Make sure to allow a provision for air in the overhangs to not be blocked from venting the attic.
Do not put a vapor barrier between the trusses and the ceiling. You want the warm moist air inside your building to be able to rise into the attic and be vented out through the ridge. And if you are going to insulate your ceiling, R-19 is really not near enough. At a minimum I’d think about R-38 or 45 blown in.
Thank you for allowing me to share some insight into insulation.
Mike the Pole Barn Guru
DEAR KEVIN: I know of several builders who would think nothing of screwing steel liner panels to truss bottom chords spaced eight and even nine-foot on center. Personally, I feel like there is going to be some noticeable deflection at those spans, especially as liner panels tend to run towards 29 gauge’s thin side. It is also, obviously, going to depend upon what is being used for insulation. Blown in fiberglass is very light, cellulose or rock wool will be roughly three times as heavy.
DEAR NORMAN: Actually, a typical 3 ply 2×6 true glu-laminated column, will be stronger than a solid sawn 6×6. This is especially true in Western states where solid sawn columns are typically Hem-Fir. Hem-Fir has a lower Fb (fiberstress in bending) than many other popular wood species. Now, some good news for you….Hansen Pole Buildings is expanding to provide metal connector plated trusses, as well as lumber and glu-laminated columns. In buying direct from a well-respected sawmill for lumber and a glu-laminated column manufacturer, we are cutting out scores of middlemen, resulting in us being able to deliver better quality materials, with shorter lead times and at competitive prices. Pricing should be available in roughly 30 days with deliveries to begin around mid-May.
DEAR BRIAN: I find concept of a plywood floor as opposed to slab-on-grade very appealing personally. Many years ago I lived in one side of a rental duplex in Coeur d’Alene, Idaho. I mention it as this duplex had radiant ceiling heat. It was fabulous as long as you were not under something (like your legs when sitting at a table). As heat rises, I would look towards radiant floor heat as my first choice (have it in our barndominium on South Dakota side of Lake Traverse). Fully engineered post frame, modest tastes, totally DIY, move in ready, budget roughly $70-80 per sft of floor space for living areas, $35 for all others. Does not include land, site prep, utilities, permits. If you hire it all done by a General Contractor, expect to pay 2-3x as much.
DEAR TIM: As far as actually damaging posts themselves, highly unlikely. If your 4×6 columns are not adequately anchored in ground by a concrete bottom collar, concrete encasement, or other properly compacted backfill, there is a potential for them to be shifted out of place when concrete is poured. Depending upon method of pressure treatment, ph of concrete against pressure treated pine can cause brown-rot fungi. If your columns were treated with ACQ-D or MCA, it might be prudent to isolate columns from concrete with a waterproof barrier. A barrier can be created as simply as running your under-slab vapor barrier (6mil or thicker black plastic) up and over top of your pressure treated splash planks and around sides of columns to top of slab.
DEAR POLE BARN GURU: Do your pole building packages meet the 2018 International Building Code and all codes adopted by Pennsylvania for commercial construction? ANDREW in HOLLIDAYSBURG
DEAR POLE BARN GURU: We own the land however we don’t where to get started with this Process? TONY in FLORENCE 
Wire not placed on chairs will not be effective. But in a rush to get jobs done, some crews eliminate chairs and roll WWM directly out over Code required under slab plastic sheeting covering underlying properly compacted fill. And when installers do use chairs, they must take care not to knock WWM off the chairs during pour. If they do, then they need to reset WWM.
Most post frame buildings have shells erected then slab poured, so this should not be an issue. A pressure preservative treated splash plank should be in place around this building’s perimeter. It will become forms for your slab. Snap a chalk line on the inside of splash planks up 3-1/2″ from bottom, this will be top of your slab. 
DEAR MICHAEL: Many different colors of “cool roof” steel are now available, which adds far more flexibility in aesthetics – one is no longer limited to bare Galvalume or galvanized, or white- 
DEAR DAYNA: The beauty of post frame buildings is a concrete slab is not required in order to support the building. As to floor plans – unless otherwise requested by a client, most post frame buildings are clearspan structures, without any interior columns or partitions. This allows for the total flexibility to place walls wherever one chooses, if any. The quickest way to hear back soon is to include an email address to send responses to.
The 2×6 top and bottom chords may very well be sufficient, as it will depend as much on the grade of the material used, than just the size. There should have been a sealed truss drawing delivered with the trusses – scan it and send it to me. I spent many years in the truss industry, so if something is amiss, chances are good I will catch it.
