Tag Archives: skylights

Vapor Barrier, Replacement Skylights, and Frost Heave

This week the Pole Barn Guru answers questions about vapor barrier, a solution for skylights, and how to reduce frost heave.

DEAR POLE BARN GURU: Vapor barrier under roof metal or under trusses with insulation on top?
I find never-ending opinions about where to place vapor barrier in a post frame building.
If the space is to be insulated would it not be better to put nothing directly under the roof metal and put a vapor barrier on the ceiling with insulation above that?
Everyone says to put on single or double bubble before putting down roof metal but if I do that how do I insulate the ceiling because then I will have a vapor barrier above the insulation. DAVID in KIRKWOOD

DEAR DAVID: Vapor barrier under roof steel if you are creating a dead attic space. It is essential to prevent warm moist air from within your attic from reaching underside of roof steel. My preference would be to use roof steel with Dripstop (https://www.hansenpolebuildings.com/2017/03/integral-condensation-control/) or Condenstop (https://www.hansenpolebuildings.com/2014/07/condenstop/) applied.

Do not place a vapor barrier between ceiling sheetrock and attic insulation. Do properly ventilate your dead attic space as Code requires (https://www.hansenpolebuildings.com/2018/03/adequate-eave-ridge-ventilation/).


DEAR POLE BARN GURU: I have a pole shed 1972? with skylights that need replacing where do I find . DAVE in COLFAX

DEAR DAVE: One of my previous questioners had a similar issue, you might want to read here: https://www.hansenpolebuildings.com/2018/08/sky-lights-leaking/.


DEAR POLE BARN GURU: What do you recommend for creating a frost wall around a post frame (posts in the ground) structure. The posts are dug down below frost level, so the footings are protected. But if the interior floor is a slab poured on grade, what is the best way to protect this slab from frost heave?
slab edge insulationThank you, CHRIS in NEW HOLLAND

DEAR CHRIS: Good to hear from you! (side note – Chris is a personal friend of mine) There is a relatively simple solution for this – do the post frame version of a shallow frost protected foundation: https://www.hansenpolebuildings.com/2017/09/post-frame-frost-walls/.


Examining a Light Steel Truss Frame Building

Examining a Light Steel Truss Frame Building

I have never owned or assembled a light steel truss frame building. A gentleman named Stan Floyd worked for me as a salesman when I owned M & W Building Supply. Stan’s dad had fabricated light steel truss frame buildings in Arkansas and Stan was interested in developing this concept in Oregon and Washington. With my blessing Stan founded Web Steel Structures in Sandy, Oregon and found out things weren’t quite like they had been in Arkansas – where building permits, if even required, were issued far more liberally. Northwest jurisdictions required engineering for both frames and buildings, as well as a need for a higher degree of control over welder competency.

Reader DEBORAH in OMAHA writes:

“Did pic come through?

Does this look viable at 30+ years old?

Tear down? I’m looking at buying this property and I’m wondering if I’m going to be the one tearing this 180’ x 85’ building down…

There are only 4 bolts holding the truss frame together at center. Bays are 18’ on center. Every other bay has a criss cross bracing with wire (X) that is of steel cable – somewhat loose. I think there is another cross at the ceiling in kind of a strange place.

I believe the purlins are 2 x 8 as opposed to 2 x 10 which might be better. Building is in Southern IL near KY border.

I think this may have been a Cuckler kit. But I’m not sure. I’ve contacted Star Buildings to see if they know.


I called an SE for a site visit and load calc and I know that will be about $12,000. It would be estimated as steel quality is unknown. Site visits for just a nod are about $900.”

Dear Deborah ~

Thank you very much for sending photos.

You are looking over a light steel truss frame building – not a post frame building. I am not a gambling man, however I would wager there was no actual engineering done for this structure to start with. Light steel truss frames, such as this, are also rarely engineered. More often than not, frame designs are just like daddy used to do them, so they must be good. Well, engineering does not quite work like this.

Some observations from your photos – minor discolorations appearing as “runs” down sides of roof purlins are due to condensation. No steel roofed building should be constructed without some sort of mechanism to minimize condensation. Only realistic fix for future condensation control would be to have closed cell spray foam insulation placed below roof surface. This insulation should be a minimum thickness of two inches and in most areas a going rate of about a dollar per square foot, per inch of thickness. You could be seeing a $30,000 bill.

Purlins with major blackness have mold due to roof leaks. This mold can be removed, but will prove to be labor intensive. I’d replace any roof ‘skylights’ with steel panels. If they have not yet begun to leak, they will in time.

Unless roof purlins are some grade higher than #2 & btr, they are over stressed in bending and likely have deflection issues. Chances are good wall girts have similar challenges.

In summary, if you decide to invest in this property I would recommend you not go inside this building when snow sticks to roof or winds are over 50 miles per hour. Insure it heavily (for non-depreciated replacement cost) and don’t keep expensive horses inside it.

For history buffs – Cuckler Building Systems division of Lear Siegler Inc. (LSI), was purchased by Star Manufacturing Company in 1986. With manufacturing locations in Monticello, IA and Turlock, CA, Cuckler had annual sales of approximately $20 million. Cuckler Steel Span Company had previously been acquired by LSI in 1970. I’d be interested in any stories about Cuckler Steel Span’s earlier years.


Triple Wall Polycarbonate Panels

There is never a dull moment in the post frame (pole) building industry. Clients are seemingly forever asking for new and different products to incorporate into their structures – which keeps life very, very interesting.

Multiwall PanelsHansen Pole Buildings recently had an inquiry from a client who wants to construct a greenhouse 24’ wide by 30’ long with eight foot sidewalls. The client specified the use of triple wall polycarbonate panels for roofing. Since I was unfamiliar with the product, it was research time.

We already purchase pallets of precut CoverLite® polycarbonate panels for use as eavelights from Amerilux, so my research began with contacting our friendly sales person there – Stephanie. She proved to be a wealth of information.

The brochure on CoverLite® Multiwall Polycarbonate panels can be viewed here: https://www.ameriluxinternational.com/SideBarLinks/Brochures/coverlite_multiwall_brochure.pdf

Now the use of these panels for roofing (or siding) takes a little more thought than applying traditional roll formed steel panels.

To begin with, these panels have no shear strength, they are not designed to be able to withstand the lateral forces applied to a building. This means the building itself must be reinforced to take the loads. The easiest method is to utilize steel strapping in an X pattern between the pole building framing and the triple wall panels. The strapping needs to be sized adequately to withstand tension forces and most importantly – fastened at each end sufficiently.

For information on steel strapping: https://www.strongtie.com/products/CFS/CS-CMST.asp

In the case of this particular client’s building – the dimensions were fairly small (24 feet wide by 30 feet long and an eight foot eave), so the strapping needs were fairly minimal. As building dimensions increase (or wind load forces to be resisted become more extreme) the strapping must be increased in strength. Shear forces are higher as the endwalls are approached, so strapping sizes and fasteners can be adjusted to meet the requirements of each subsequent bay.

The CoverLite® Multiwall Polycarbonate panels are square, so they do not afford an overlap. The seams between each panel must be joined by means of an H profile trim. As the ends of each panel are open, a U trim must be installed at the top and bottom of each panel, to help prevent moisture from accumulating between the layers. The U at the eave side of the panels must have holes strategically placed to allow for any condensation to run out the low end of the panel.

Looking to do a greenhouse pole building roof in style? Then look no further than to have a properly engineered post frame (pole) building with CoverLite® Multiwall Polycarbonate panels.

Single Slope Pole Barn

When the Requests Are Interesting

My encouragement to potential clients is to share with us your troubles and your goals – and let us structurally design for you the best solution which is a marriage between wants, needs, budget and available space.

Finding happiness in a new building, is much akin to success at finding the person to become the “ideal” spouse. If one goes into either situation with too much advice from well-meaning friends and lots of preconceived notions as to what they think they want, chances are the satisfaction level with the experience is going to be less than it could or should be.

Here is an actual recent request:

Single Slope Pole Barn“I will be building a single slope (roof and 3 sides covered with corrugated steel) pole barn similar to one of your designs online.  My ideal design is 20 by 30 with 1 foot roof overhang.  The structure consists of (3) 20 x 10 bays.  High side to be 12 feet and low side to be 10 feet with bay entry at high side.  I will only consider steel posts (8) for the vertical pole construction.  For the roofing material please include 2 each opaque roof sheathing for each bay (natural lighting).  Design to include high wind (50 mph) with 18″ snow load.  Please provide a detailed bill of material including foundation (30 to 36 inch footing depth (no slab) with bid.  I will be requesting engineered drawings.  The shipping destination is xxxxx zip code so please include shipping total and tax in bid.

I look forward to receiving your bid and perhaps purchasing your product.”

Obviously, this person felt they had their solution pretty well figured out…..

Except they neglected to do any research, which would have saved them from having to write out their wants and click submit!

Here is my take on their request:

Single slope buildings are rarely the best practical design solution. https://www.hansenpolebuildings.com/blog/2014/11/single-slope-roof/

With the building sloping only two feet across 20 feet, the 1.2/12 roof slope is not going to be conducive to moving weather off (rain or snow) and is so flat the steel warranty will be void.

Here is where the two of us are most certainly not a fit: “I will only consider steel posts (8) for the vertical pole construction.” As we don’t use columns other than wood, the specifying only considering the use of steel posts, eliminates us (as well as many others) from possibly being suppliers. The use of only eight “posts” means the 20 foot walls are going to have to span from corner column to corner column – while this might not be an issue in all steel construction, wood wall girts will be hard pressed to meet this criteria.

It also means trusses or rafters which must clearspan the 20 from wall-to-wall, which could significantly affect both project cost, as well as the interior clear (vertical) height.

For the roofing material please include 2 each opaque roof sheathing for each bay (natural lighting).” This request, especially given the near flat roof slope, is probably dooming the finished product to at least roof leaks, if not worse.

Read more about roof skylights here: https://www.hansenpolebuildings.com/blog/2014/09/skylights-2/

This client has not done his homework, as 50 mph (miles per hour) is not a high wind speed when the minimum Building Code requirement anywhere in the United States is 85 mph.

More on wind speeds here:


The 18 inch snow load is not going to be what his Building Official has in mind either: https://www.hansenpolebuildings.com/blog/2013/11/design-criteria-3/

And, of course, no true pole building kit package supplier worth their salt is going to hand out a materials’ list prior to a client ordering. Why not? Read this: https://www.hansenpolebuildings.com/blog/2012/03/materials-list/

While we do include delivery to the site as part of our quotes, sales taxes are typically a different situation altogether as noted here:


Perhaps the requirement of engineer sealed drawings will help to steer this client closer to what might be a more practical and affordable design solution while still getting his ultimate goal – a single slope roof design.

Dear Guru: Where Can I Get FRP?

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:I am wanting to replace the frp skylights on an older metal building but don’t know the brand or where to find some that will fit. the ribs are 10″ o.c. 1/2″ tall 1 1/2″ wide flat tops. any ideas? thanks. HAULING IN HEYWORTH

DEAR HAULING: FRP (Fiberglass Reinforced Plastic) panels used in steel covered buildings can be problematic (as you have found out).

More information on FRP can be found at: https://www.hansenpolebuildings.com/blog/2012/01/skylights/

Depending upon the age of your building and the manufacturer of the steel panels, a replacement polycarbonate panel may be available. Over the years, many steel roll formers, who had unique panel profiles, have either closed their doors, or have been bought out. As such, you may have a profile which is impossible to match.

With some photos and perhaps more dimensions, chances are good if it is a currently produced profile, we can find a solution for you.


Do you have any “garage plus living area” pre-made plans? I own some vacant land and I want to put a pole building/garage on my property that would be approximately 32×32 for the garage part. In addition I want some living space on the garage that I can put some living quarters. I do not want an entire house, rather simply space for a living room and a bedroom.

Do you have any plans that are close to what I am looking for? THOUGHTFUL TREVOR

DEAR THOUGHTFUL: Thank you for your interest. As everything we do is custom designed to best meet the needs of our clients, we do not have any ready made plans – however any of our Building Designers would be happy to work with you to create your ideal dream building.

DEAR POLE BARN GURU: I emailed and got a quote from you back in March on a 36’ x  56’ pole building, I liked your numbers but I have enclosed my material list & drawing of the way I will do it. I have been a carpenter for 30 years so I will be doing it myself. We will be starting building on August 4th so we will be starting construction pretty soon. Can you break down the metal price separate from the lumber price? We are building in Powell WY. PONDERING IN POWELL

DEAR PONDERING: We can certainly appreciate the skills of a qualified carpenter, they are many. The Building Codes have become so complex, over the past decade, we typically shy away from providing structural materials from a pre-prepared list. In order to assure your (or any) post frame building kit package we prepare is indeed Code conforming and capable of withstanding the climactic conditions, our normal procedure is to work from your needs and to design a building which we are assured we last for not only your lifetime, but those of future generations. If you have particular preferences for column or truss spacings, as well as girt or purlin spacing preferences, we can most usually work with those – again as long as they meet structural requirements. We will never under-design a building, but if you want it “beefed up” so you “sleep better” – it’s ok by us.

Mike’s Roof Rules

Nothing is worse than a roof gone wrong. Leaks frustrate everyone involved, and are usually avoidable. Poor design and poor installation are equal factors in the roofs which just are not happy.

Avoid Valleys

Pole Barn Roof With ValleysDesigning the roof of a pole barn? Then try to design a roof without any valleys. Valleys concentrate water and often clog with ice. It’s far more common to have leaks or ice dam problems near valleys than in the middle of a simple gabled roof. Many valleys exist because of a designer’s conceit rather than necessity. Often, these valleys trace back to the mistaken belief a chopped-up, complicated, multi-plane roof looks better than a simple gable. It doesn’t. And more complicated roofs are more expensive.

Just say no to Dormers and Skylights

Dormer Pole BarnNo good reason exists for a new pole building to have a dormer. When I see a dormer, I conclude the designer or the architect made a mistake. They didn’t include enough interior space, and the building owner was forced to cut a hole in the roof because the ceiling was too low to stand up. Want to build a multi-story pole building – no problem. Want two floors, build two floors. Want three floors, build three floors. Then build a roof over the top floor. This roof should not have any deliberate holes in it. The “no holes” rule covers both dormers and skylights. Skylights are an invitation to leak – no matter how great the flashing kit is, pretty well plan upon them leaking, if they don’t it is a surprise bonus.

In most cases Single Slope Roofs are not less expensive

They also create a very tall wall on one side of the building, which has to be engineered for. Lots of “dead air” space ends up being paid for. There is not a ridge which can be easily vented. Worst of all – most people find them aesthetically unattractive.

An Unconditioned Vented Attic is better than an Insulated Roof

It makes more sense to put insulation on a flat ceiling than to try to insulate a sloped roof, for several reasons. Purlins usually aren’t deep enough to hold a thick layer of insulation; on the other hand, it’s usually easy to add a deep layer of insulation to the attic floor. Insulating the attic floor is also cheaper. Leave the space between purlins uninsulated, it will be easier to locate roof leaks. It is easier to air seal a flat ceiling, rather than a vaulted ceiling. If roof sheathing is used, damp roof sheathing will dry out quicker if it faces an attic than if it is part of a cathedral ceiling.

The Best Roof Shape is a simple Gable Roof

In a cold climate, the ideal design is a simple gable. Since gables don’t have any valleys or hips, they are easy to vent. It’s a straight shot from the soffits to the ridge.  Chopped-up roofs with a variety of intersecting planes are hard to frame, hard to keep watertight, and hard to vent. Every nook and cranny creates somewhere for tree needles and ice to accumulate.

In a hot climate, a hipped roof can make more sense than a gable, because a hipped roof makes it easier to provide shade on all four sides of the pole barn. In a hot climate, shade is good. Fortunately, people in hot climates rarely have to worry about ice dams.

In all climates, make overhangs generous. If  building a gable roof, don’t forget the rake overhangs; most rake overhangs are too stingy. Frame the rake overhang with overhanging purlins.

Don’t reduce the Roof Slope between the Ridge and the Eave

Pole Barn - Shallow Slope RoofA good roof plane has a consistent slope from the ridge to the eave. A roof which changes slope at midpoint is disturbing. Especially disturbing is a steep roof which suddenly switches to a shallow pitch (for example, when a porch with a shallow-pitched roof is affixed to a pole building with a steep roof). Shallow slopes hold snow and are susceptible to leaks. Most steel roofing warranties are void on slopes of less than 3/12.

Make sense so far? Come back Monday when I finish up on my recommendations for making your roof affordable, long lasting, and pleasing to the eye.

Polycarbonate eavelights: Light up my Life

One of our Building Designers, Alan, is a former general contractor who, prior to becoming a Building Designer, had constructed about 200 Hansen Buildings in several Pacific Northwest states.

This morning, he sent me an Instant Message as a client had asked if they, “could have eave lights in the roof of their building”?

Polycarbonate Eavelights

Traditional “eave lights” were opaque fiberglass (actually fiberglass reinforced plastic) panels which have roughly the same rib configuration as the wall steel. Placed at the tops of the eave sidewalls, they would allow for affordable light transmission into the building.

The downside of fiberglass is the panels have a very low tolerance for UV rays from the sun. They quickly degrade, turning yellow and becoming brittle. This means they can crack and break. Besides the less than attractive “yellow” color, the amount of light transmitted through them decreases as the yellow color increases.

A better product exists – polycarbonate panels. Polycarbonates (with trademark names such as Lexan) are very durable and have high impact resistance. Polycarbonate eavelight panels have better light transmission characteristics than many kinds of glass.

Now pole buildings work like uni-body cars, the “skin” of the building transfers shear loads (from wind or earthquake) through the roof, to the endwalls and then down to the ground. When checking the design of the building, the “load path” needs to be checked to verify the clean transfer of forces at each material transition.

Steel roofing, like oriented strand board (osb) or plywood panels (when the correct product is properly installed) will allow for the horizontal transfer of shear loads. Polycarbonate eavelights or “skylight” panels, while able to withstand impacts and carry loads perpendicular to the surface, are not rated for carrying shear loads.  Does this mean you can’t use them on roofs?  Not exactly.

Polycarbonate panels can be used as “skylights”.  However, depending upon the loads attempting to be transferred – the framing of the roof may need to be reinforced, and steel cross strapping added across the polycarbonate locations.

While not a big fan of putting “skylights” in roofs (they are a leak looking for a place to happen), I have seen some good applications, with careful installation including meticulous sealing.  If you are set on having them, please at least consider hiring the installation out to someone who clearly has installed them before and you have reasonable expectation they “know what they are doing.”

The most affordable solution to add light through the roof is to use translucent ridge caps. The peak of the roof is the zero axis of shear loads on the roof – making this the ideal structural location.  And this is something the average homeowner can install.

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