Mushroom warehouse may be world’s largest pole barn

By Sharon Thatcher, Rural Builder
Is there anything in low-rise construction you can’t do with post frame? It would seem not to Reuben Graber and his truss designer Dave Hurst. They rarely walk away from a post-frame challenge and may likely hold the record for the largest pole barn in the world.

Largest Pole BuildingGraber is owner of Graber Supply, LLC, Atglen, Pa. No other state in the U.S. produces more mushrooms than Pennsylvania and Graber sits smack-dab in the middle of mushroom country, yet for several years, Graber Supply ( did very little work on mushroom farms, at least not with barns for growing. That changed about four years ago when they created a barn over 200 by 560 feet that was supported by a unique truss system designed by Hurst.

To understand the design, you need to know a little about the typical mushroom barn and how mushrooms are grown.

“They have various bays or dark rooms where they grow these mushrooms,” Graber explains. “And they may be growing them there at a lower temperature, 40 degrees I think is required, and then when they clean out the bays, they have to steam clean everything with temperatures of like 140 degrees.”

Each room is self-contained so while one room is being sanitized at 140 degrees, another room next door will still be growing mushrooms at 40 degrees. Good insulation is critical.
Also important are tight seals around every single opening in and out of each room. “Those connections had to be totally sealed tight because even if one little spore gets in there, because of the nature of how a mushroom grows, it could grow wild and destroy the whole crop,” Hurst explains.

In the past, most of the local mushrooms houses were built with concrete. “Most of these houses in this area are old and need repair or replaced and most were made out of concrete when concrete was cheap, labor was cheap and it didn’t cost as much to heat,” Hurst says.

At today’s prices, keeping such a structure climate controlled would cost a fortune to insulate with a concrete build. “And because our mushroom-growing client had developed a new way of growing them, they needed a large, wide open building,” Hurst notes.

Stick-built was an option but that would have meant placing studs every 16 inches. That was unacceptable because those studs would create a thermal break and increase the difficulty for insulating.
The Graber-Hurst solution dealt with the critical factors of insulation and airtight seals with poles placed 8-foot on center. Conversely, it created a new problem: how to construct it.
To design such a building as a first-ever post frame is not for the faint of heart, but Graber was confident in Hurst. “Dave Hurst has been with us since about 1995, and he’s just a very brilliant designer and he worked in the truss industry in engineering design and he came to us with just a wealth of knowledge about design. He was able to apply a lot of that to this particular building,” Graber says.

The company was led to the job by Double T Equipment of Airdrie, Alberta, Canada, a German company that had been hired by the owner for the state-of-the-art interior mechanics. “They contacted us to work with them to design this building around their concept,” Hurst says.

The biggest challenge was the truss system. “A normal post and frame building has a 4:12 pitch, but you could not do that with this building because of the 200 foot width,” Graber says. “At 200 feet wide it would just get astronomically high. A typical steel building has a flatter slope, maybe a 1:12 pitch, so we were able to run the trusses in the opposite direction with some cantalevers and inverted designs to come up with a 1:12 pitch for this building. It’s very unique in design and I don’t think the competition was ever able to get there and figure it all out. This was a totally new creation for us, totally from scratch.”

The solution for keeping each growing room temperature-controlled came in the form of an R30 insulation wall design.

Air tightness was solved with an elastomeric coating and lots of caulk. “The whole thing, everything, is totally covered in plastic,” Hurst describes. “Every room is separated in plastic before the wall sheathing is put on. Every penetration had to be caulked.”

On the roof are custom-built cupolas. “The key challenge was getting the structure put up, but the next one was getting air flow in there. We needed a certain amount of CFMs for intake versus exhaust and so we had to do special-made cupolas and ventilation. The airflow in this design is very critical,” Hurst explains. “The air handler has a very fine, small micron filter.”
While the side areas of the building are 16 foot high, the aisle down the center of the building clear spans 20 feet to handle the air handlers that blows air in and sucks air out as needed.
The end product provides the owner with 24 growing rooms downstairs – 12 on each side – plus a room for processing and refrigerating the mushrooms, and a two-story mid section for storage and office space.

Laminated poles and trusses for the building were acquired locally. The metal skin on the building came from Graber Post Buildings, Inc., Indiana.
So far, so good. The building has survived a few major snowstorms, including one in particular. “We had one big snowstorm three years after it went up and a number of buildings fell around it, but it held up,” Hurst notes.

Unfortunately this building went up right as the economy went down and the mushroom industry has yet to rebound. When it does, Graber is hoping to see more post-frame mushroom barns bearing the Graber name.

The man behind the company
Having grown up around the pole barn business, the last thing Reuben Graber wanted was a life of pole barns. Something happened on his way to a career in banking.

If the name sounds familiar, yes, Reuben is related. The owner of Graber Post, Montgomery, Indiana, Glen Graber, is his cousin. Reuben grew up around pole barns in Missouri and even had his own construction business after high school. “I spent a couple years building pole barns. I went out and hired a couple guys and we went out and constructed these things when I was 23, 24 years old,” he explains.

He started college at age 25 and majored in marketing. “When I graduated I had hoped and planned to get into banking, maybe as a commercial loan officer, and grow up into management,” he says.
Cousin Glen had other ideas. “My cousin Glen is really the one who talked me out of it. As I was coming up on graduation he kept calling and saying, ‘now, how much money are you going to earn at that bank?’ I finally had to admit to him that the best offer I had was about $23,000 and they were going to take money out for my health insurance. We were in a recession, this was 1990, and we had just gotten into the first Iraq war. I was married by then and had a kid on the way.”

He was living in Pennsylvania and started his own business there in Chester County.

“I started selling garage doors out of my garage,” he continues. “Next thing I rented the backside of an old corn crib… There was no pavement on the parking lot, just gravel, and that was my first facility, with a fork lift that would barely run.”

Selling metal came next. “We started getting truckloads of metal from Graber Post in Indiana. I’d go out and deliver this stuff all along the east coast with a goose neck trailer and a 2-ton truck.”

He started stocking metal along with trim and screws. He was soon in need of a larger building. His next step was to purchase 30 acres of commercial property on a state highway a stone’s throw from Lancaster County. Their current business has an 80-by-200-foot post-frame structure with 20-foot ceilings. It houses a supply store, warehouse and office. Several supporting buildings have since been added on the property.

Everything is available to the builder under one roof. “We started stocking lumber and grew into designing buildings and of course selling the material to builders and the end users as well, and putting the whole kits together,” Graber explains. “If the customer doesn’t come with a builder, we’ll provide one, we’ll take the responsibility for getting it constructed. We’ll sub out the construction to some of the crews locally.”

Graber Supply now sells in nearly a dozen states along the east coast.

In 2004, Graber added a similar facility, Kalona Post & Frame ( in the small community of Kalona, Iowa.

“When I made the decision to start this in Kalona, the local town people said, ‘oh you know this is not the east coast, you can’t just start a business from scratch out here. There’s no market.’ I said, if nobody starts anything it isn’t going to grow for sure, so we opened up in 2004 and it’s growing. It does business in southern and central Iowa, Illinois and down into Missouri.”

He isn’t done expanding the pole barn supply business yet. More expansion at the Pennsylvania store is planned. “We’re actively growing and expanding,” he says. “We have 30 acres here and so far we’ve only developed about 5 acres of that. Over the course of the next several years we have plans in place to develop up to 20 of the 30 acres and leave about 10 acres of green space.” Expect a new main building to be another post-frame phenom.

Today, Reuben is glad he listened to his cousin Glen and returned to the post-frame business. As he admits in hindsight: “I can’t imagine what my life would have been like if I had gone into banking.”