Tag Archives: FRP panels

Old Skylights

Back in the day I spent a year working for the now defunct Mac Truss Company in McMinnville, Oregon. Not long after I began working with them, they decided to relocate their manufacturing facilities across town to an old machine shop. All was fine and good with the move, until the fall rains began.

Fiberglass Eave LightsThe machine shop happened to have fiberglass (FRP) skylights, which had yellowed so badly they let in less light than the adjacent steel panels. One thing they DID let in – was the weather. Not only had the FRP panels turned color, they had also become brittle and cracked. It was bad enough working in a fairly dark building, even worse when the just above freezing rains came in!

For the most part, pole building suppliers and builders have recognized the inherent challenges of trying to use light panels in roofs – very rarely does one see them installed in new buildings. Which is good, as neither FRP, polycarbonate or acrylic panels are designed to withstand shear loading (weight of anything on the roof – like ice and snow) so their use not only weakens the roof diaphragm, it also creates a future failure. A failure – in my humble opinion – being when they fracture around the fasteners due to loads they were not intended to carry and begin to leak!

Another long, hot summer has ended and people with older buildings with failed skylights are beginning to look for solutions to their building’s problems. Hardly a day goes by, which does not include an email from someone trying to find replacement panels for their old fiberglass skylights. Almost always these requests are for some panel configuration which has not been used as common practice for years.

In the event you are one of these building owners, my best recommendation is to take the photographs of your panels (clearly showing the panel profile) to the contractor desk at your nearest The Home Depot® or Lowes®. If the profile is available, either should be able to find a suitable replacement.

For more reading on skylight panels: https://www.hansenpolebuildings.com/blog/2012/01/skylights/ and https://www.hansenpolebuildings.com/blog/2014/02/acrylic/

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.


A request we receive frequently is for skylights to be installed in the steel covered roofs of our pole buildings.

My first thoughts go back to a building I worked inside of over the winter of 1980-81. About 20 years old, the building had a steel roof with numerous fiberglass (actually Fiberglass Reinforced Plastic or FRP) panels in the roof. These panels were designed and placed with the intent of allowing natural light into this very large building. The operative word here being “were”.

FRP panels are strong mold-resistant sheets. Over time the glazed pigmented seal applied during the manufacturing process can crack causing the structural breakdown of fiberglass resin by weathering. In the case of this particular building, the skylights had deteriorated to a less than lovely yellow color, allowing very little light transmission. Lateral loads being transferred through the roof from wind had elongated the holes around the screws, causing numerous roof leaks.

Brittleness over time is another issue with FRP. At the first truss manufacturing plant I owned, we constructed a new building in 1982, with FRP panels at the top of the south facing sidewall. The idea was to be able to gain natural lighting. Within a matter of just a few years, the panels had yellowed and become brittle. Local kids, out for “fun” were throwing rocks through the panels!

Available technologies have improved. For use in pole buildings, most instances where FRP panels would have been used, the work is now being done by polycarbonates.

Polycarbonate panels are designed specifically to match up to the metal panel profile. With a high performance glazing which stands up to punishing exterior applications, Polycarbonate Panels offer multiple advantages over traditional FRP panels: up to 20 times greater impact resistance, the highest light transmission rates, the lowest yellowing index, the highest load rating, and the highest resistance to wind uplift-outstanding properties confirmed in accredited laboratory testing and in installations worldwide since 1984. Polycarbonate panels are virtually unbreakable, they self-extinguish if exposed to flame, are hail resistant and are Underwriters Laboratory (UL) 580 Class 90 recognized.

Polycarbonate roof panels are normally used as in-plane translucent panels and are used with steel panels. Instead, we recommend these skylights be used in the walls as eave lights to allow light into the building to prevent anyone from walking on these panels.

If you are really planning on using polycarbonate roof panels, then you cannot insulate the roof in these areas, or you will block all the light. Roof areas without a good vapor barrier, which would be provided by properly installed insulation, are prone to condensation issues as well. You’ll also have to take some precautions about thermal movement. Polycarbonate panels do expand and contract much more than steel panels and they are much weaker and deflect more.

We’ve had an engineer perform full scale testing of steel panels similar to what is used on your new Hansen Pole Building (our tests were performed using thinner 30 gauge steel). These tests resulted in shear values for these panels being published in the National Frame Builders Association (NFBA) Post-Frame Building Design Manual. With a minimum allowable shear strength of 110 pounds per lineal foot, this steel is identical in strength to 7/16” oriented strand board (osb) installed in an unblocked diaphragm (no blocking at the seams between the sheets of osb).

Properly installed steel roofing, has the shear strength to be able to transfer loads induced by wind or seismic forces across the roof, through the building endwalls, to the ground. Herein lies the issue with light panels (either FRP or Polycarbonate).  They have no shear strength. In adding light panels, the structural integrity of the roof could be compromised. Under lateral loads, the panels could fracture or buckle, or the building frame itself could be overstressed.

There ARE some solutions as well as alternatives. Least costly would be to utilize light panels at the top of one or both sidewalls, or in the triangle area of one or both gable ends. Another affordable option would be to use a translucent ridge cap.

If light panels absolutely must be installed in the plane of the roof as skylights, the area can be reinforced by using steel strapping as an X from truss to truss on top of the roof purlins. This X will be seen through the light panels in the roof.  Aesthetics of the roof may be a consideration, especially with steeper sloped roofs where it is easily seen from the ground.  Also, while this solution adds to the cost of materials, as well as slows installation, it does afford a solution.