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A 100×100 Pole Building, Shingles to Steel, and Double-Bubble

This week the Pole Barn Guru answers reader questions about the possibility of a 100′ x 100′ pole building, the consideration of switching from asphalt shingles to steel roofing, and if one can reuse the “double-bubble” when replacing roof steel.

DEAR POLE BARN GURU: Can I build a 100 ft X 100 ft. pole building? JOHN in PENSACOLA?

DEAR JOHN: While 100 foot clearspans can be achieved using post-frame construction, most building uses do not have this sort of requirement. In general, it will be far more cost effective to get your 10,000 square feet with a rectangular footprint of 60 to 80 foot in clearspan width. If you are limited, by property constraints to 100 x 100, but do not necessarily have to have a clearspan, a row or two of strategically placed interior columns can assist in keeping your building investment down.

DEAR POLE BARN GURU: I’ve got a question for you finally. I have a house with asphalt shingles at the moment and was thinking about switching to steel. If I were to remove the shingles, would I need to place latticed boards to keep the steel roof off the plywood to provide room for air movement? I’d use whatever underlayment is approved for the steel, but looking at a lot of your posts and comments, it’s got me wondering if I’m better off just going back to asphalt shingles instead and saving a lot of extra work.

I’m curious if in the case of placing the steel on the underlayment could cause some issues with condensation that may or may not make its way down the underlayment and off the roof. Would hate for any condensation to find its way into the plywood and become locked in causing rot. SETH in GRAND FORKS

DEAR SETH: Let’s start by looking at downside of shingles – https://www.hansenpolebuildings.com/2015/03/shingle-warranties/ and from Tim Carter https://www.hansenpolebuildings.com/2018/10/ask-the-builder/

For condensation to occur on underside of steel roofing, warm, moist air from your attic must be able to come in contact with roofing. Your plywood with an appropriate underlayment provide a thermal break keeping this from happening. You do want to make sure you have adequate eave and ridge ventilation https://www.hansenpolebuildings.com/2018/03/adequate-eave-ridge-ventilation/

Here is an actual “how I did it” story for you: https://www.hansenpolebuildings.com/2018/06/how-to-install-a-steel-roof-over-shingles/

DEAR POLE BARN GURU: I’m replacing my screwed down corrugated steel roof because the installer kinked the metal in a few places. Can I use the same double bubble vapor barrier or must i replace the vapor barrier too? It has a few holes in a few places in addition to the staple holes they made when applying it. JAVO in PRINCE FREDERICK

DEAR JAVO: Double bubble or other reflective radiant barriers only work to control condensation when they are 100% air sealed. You would be money ahead to order your replacement panels with an Integral Condensation Control factory applied and throw away your old double bubble. Please read more here: https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/

This entry was posted in Insulation, Ventilation, Pole Barn Questions, Alternate Siding, Pole Barn Design, Building Styles and Designs, Building Interior, Roofing Materials, Columns, Constructing a Pole Building, Pole Barn Planning, Trusses and tagged asphalt shingles, condensation control, double bubble, double bubble radiant barrier, A1V, pole building span, steel roof, interior columns on September 27, 2023 by admin.

Insulation and Ventilation, Straw Bales, and Double Bubble

This week the Pole Barn Guru answers reader questions about using cardboard and heavy plastic to vent and insulate a pole building, use of straw bales an insulator, and best way to ventilate and reduce roof noise.

DEAR POLE BARN GURU: On my 42×63 2 story pole building (heated first floor) I have trusses 9’ o.c. standard roof purloins 2’ o.c. I was wondering if I could use cardboard up against steel roofing for venting air flow of the humps in the steel roof panels (standard steel w/ 1” humps not standing seam ) then install heavy plastic on bottom of purlins and fill cavity w/ cellulose blown insulation. Would this work correctly for ventilation of steel and insulate correctly. Combination of being cheap/frugal and I have free heavy cardboard from washers/dryers/refrigerators to fit between purlins. Greatly appreciate your opinions. Thank you. BEN in EDEN

DEAR BEN: Code requires a one inch minimum of airflow across your entire roof surface above batt insulation. Air flowing only at steel ribs would be inadequate to meet requirements. Assuming you have 2×6 roof purlins, 5-1/2 inches of blown cellulose would give you roughly R-19.25. You would be better served by using 2-1/2 to 3 inches (R-17.5 to R-21) of closed cell spray foam applied directly to underside of your roof steel, as it does not have to be vented above.

DEAR POLE BARN GURU: Hi, I read your post on bale infill with a pole building (https://www.hansenpolebuildings.com/2013/04/straw-bale-homes/). When I called to get more info, the rep told me that Hansen strongly advises against it, but he also said he hadn’t heard about that idea. Is there someone there that has worked with a client who has used straw bale walls to infill between the posts? KEVIN in RENO

DEAR KEVIN: Your call happened to be routed to one of our newer Building Designers. Post frame construction is highly complex, with a literal unlimited number of possibilities, this being one your designer was unfamiliar with.

In general straw bale homes seem to have been a passing fad, however if you strongly feel this is your best option, please call again and ask to speak with Rachel – our most senior Building Designer, and she can assist you better.

DEAR POLE BARN GURU: I am looking for a underlayment for my pole barn. I have metal roofing with horse stables below. There are no side walls to my pole barn. It’s all about ventilation for the animals here in NC. It’s supposed to add a few degrees in R value. It also helps deaden the sound of rain. Everyone talks about double bubble but this is supposed to be different. Thank you, FRANCES in TRYON

DEAR FRANCES: Without having to pull off your building’s roof steel, install some fashion of condensation control then reinstall it – there is only one practical solution – two inches of closed cell spray foam applied directly to underside of your steel roofing. This would provide an R-14 insulation value. It is unlikely to have an effect on reduction of noise from rain, as it is not good at blocking sound waves. “Double bubble” offers little to no R-value and would require being installed between framing and roof steel.

This entry was posted in Roofing Materials, Pole Barn Planning, Ventilation, Building Interior, Insulation, Pole Barn Heating, Pole Barn Questions, Pole Barn Design and tagged straw bale insulation, insulation, spray foam, Ventilation, straw bale pole buildngs, double bubble, underlayment on July 20, 2022 by admin.

Condensation Control, Home Plans, and Grade Changes!

DEAR POLE BARN GURU: If I put double bubble under metal on roof for condensation control, then insulate bottom chord of trusses with white vinyl faced insulation , will this create a problem if I ventilate attic space ? Thanks. SCOTT in DUNLAP

DEAR SCOTT: You actually have several things going on here. First, single bubble reflective radiant barrier will do everything double bubble will, at a far lesser investment. The difference in the minimal R value is a fraction of one! Your building ceiling should not have an additional vapor barrier, you want the moisture from inside the building to be able to migrate through into the ventilated attic space. Blowing in an appropriate thickness of fiberglass or cellulose insulation will be far more effective, probably less expensive and will allow the moisture through. Make sure to have adequate intake at the eaves and exhaust at the ridge to be able to properly vent the dead attic space.

DEAR POLE BARN GURU: Hello!

Do you all also finish the interior of pole barns if we want it to be a home or would I contract that separately?

Thanks! TIFFANY

DEAR TIFFANY: Thank you for your interest in a new Hansen Pole Building. We provide the custom designed plans, materials delivered to your site and assembly instructions for the shell and load supporting portions of your new building only. Any interior walls and/or interior wall finishes would be up to you to contract for.

DEAR POLE BARN GURU: Can I build a pole building home in the side of a hill, where the back will be below grade and the front above. RICK in CLEAR LAKE

DEAR RICK: Most certainly you can. I have a post frame building on the back of our property outside of Spokane, Washington. The site has 12 feet of grade change across the 40 foot width. After excavating the area where the building would be placed to level, ICF blocks were placed 12 feet high along the southern wall, stepping down with the slope on the east wall, with the other two walls being “daylight” and utilizing traditional columns embedded in the ground. You can read more about my building here: https://www.hansenpolebuildings.com/2013/06/garage/