Wood-framed structures have more than proven they are capable of longevity and durable performance. The Stave Churches in Norway were constructed after the year 1100, in the Middle Ages. Twenty-eight of these structures are still standing today.

Using today’s engineered wood products and chemical preservatives, wood-framed structures can be even more durable than history has shown. With modern technologies, wood is increasingly the structural material of choice.

A growing number of buildings are being constructed using post-frame -- churches, schools, strip malls, firehouses, public buildings, warehouses, convenience stores and shops, just to name a few.

Professional engineers agree; contemporary post-frame buildings are highly engineered and proven to be excellent permanent structures.

What Makes Post-Frame So Durable?

1. Posts in the ground add to a building’s stability and wind resistance.
Post-frame buildings often utilize treated wooden posts, concrete columns or piers that are embedded directly in the ground. This provides an efficient load path directly to the ground. Building posts are typically pressure-treated with preservatives approved by the Environmental Protection Agency (EPA) or other approved wood protection systems in accordance with standards set by the American Wood Protection Association (AWPA). Building with posts offers greater structural stability with fewer materials and the capacity to build a much higher sidewall than conventional wood-framed construction.

2. Post-frame provides assurance that a building will last.
Some people may have an experience replacing a deck or fence after a several decades of use and presume that post-frame buildings will only last about the same amount of time. The public at large and even some construction industry professionals mistakenly think that all treated wood is the same and will always perform in the same way in different applications. However, the fact is there are many different categories of treated wood for various purposes. Treated wood for post-frame contains significantly more chemical preservative than is found in most treated wood, and the chemical is embedded more deeply within the wood’s structure.

Post-frame buildings may also be installed atop a concrete slab or masonry wall. There are a growing number of enhanced wood protection products and concrete posts and piers developed specifically for post-frame.

Use of quality products and installation practices will ensure a post-frame building will last. When the right materials are properly installed in either a treated wood or concrete foundation, performance is assured by quality of design, materials and workmanship.

3. The structure forms a tremendously strong box that effectively resists wind and seismic forces.
Outstanding structural performance of post-frame buildings under adverse conditions, such as hurricanes, is well-documented. Professor Gurfinkel, in his wood engineering textbook, cites superior performance of post-frame buildings over conventional construction during hurricane Camille in 1969 . Scientific research verified post-frame buildings constructed according to engineered plans generally withstood hurricane Hugo (wind gusts measured at 109 mph). A case study regarding the performance of post-frame buildings in areas ravaged by hurricanes Rita and Katrina in 2006 appears at the end of this chapter. Since post-frame buildings are relatively light weight and benefit from diaphragm action, they efficiently resist wind and seismic forces.

4. Post-frame’s diaphragm action efficiently uses materials to resist lateral forces, for an effective and inexpensive bracing system. iii
Post-frame buildings benefit from the unique properties of diaphragm action, which allows fewer building components to work together more efficiently to increase the structure’s strength and resiliency. A building diaphragm is a structural assembly comprised of structural sheathing (e.g., plywood or metal cladding) fastened to the framing in such a manner that the entire assembly is capable of transferring in-plane shear forces. 

Diaphragm Action is the transfer of load by a diaphragm. Diaphragm Design incorporates the design of roof and ceiling diaphragm(s), wall diaphragms (shearwalls), primary and secondary framing members, component connections, and foundation anchorages for the purpose of transferring lateral loads to the foundation.

Diaphragm design procedures more accurately account for the effect of diaphragm action on post and foundation design than traditional engineering practices. New roof panel assemblies that use high-strength steel and customized screw fasteners have dramatically improved diaphragm stiffness and strength. Post-frame construction has been further enhanced by the developments of metal-plate connected wood trusses, nail- and glue-laminated posts, high-strength steel sheathing and fasteners, and improved diaphragm design methods. Developments in metal-plate connected wood truss technology allow clear spans of 100 feet or more. Engineered components such as laminated posts and structural composite lumber may be obtained in a variety of sizes and pressure preservative treatments, offering advantages of superior strength, dimensional stability and enhanced stiffness. 

“We’ve been in the post-frame business since 1962,” says building material distributor Kevin Wiggam of New Washington, Ind., “and some of our older buildings have been torn down because they were no longer needed, but many are still there just as sound as the day they were built.”

A Low-Maintenance Building

A wide variety of exterior finishes may be used on post-frame buildings. Although almost any type of exterior finish may be used on a post-frame building, many utilize steel panels for siding and roofing. Steel panels are quickly, easily and economically installed, and they can provide decades of low-maintenance service.

Not all steel panels perform in the same way, even if they may look identical when purchased. The performance of steel panels depends on the types of substrates and coatings specified, and care should be taken to match customer expectations with panel performance. Steel panels with high-quality substrates and coatings will provide decades of service life with little need of maintenance other than periodic cleaning.

Steel panels are available in two different substrates - Galvanized and Galvalume. Galvanized substrates are coated with an alloy of zinc, and Galvalume substrates are coated with an alloy of zinc plus aluminum. A thicker zinc coating will provide more protection against corrosion. 

The most popular coatings for steel are polyester, siliconized polyester and PVDF. These coatings primarily vary in their ability to resist chalk and fade. Consult with panel manufacturers to determine the best substrate and coating for your specific expectations and application.

Metal siding and roofing may be integral parts of an aesthetically-pleasing building. There are various ways to improve the aesthetics of ribbed metal wall panels, as well as other building facades. Some metal-clad buildings may suffer from a lack of basic architectural features that building owners have chosen not want to invest in, such as roof overhang, entryways, porches, porticos, canopies, guttering, window and door trim, shutters and landscaping. Inclusion of these and other design features can dramatically improve a steel-clad building’s aesthetics. Also, consider:

• Roof options such as eave overhang, fascia, Mansard, Dutch, clerestory hip or gables
• Complimentary cupolas or other accoutrements
• Color-coordinated fasteners and trim
• Horizontal steel siding, standing seam roofing and/or other options that conceal fasteners
• Color-coordinated steel wainscoting
• Brick, cultured stone, wood or other wainscoting to compliment metal siding above
• New metal panel and roofing options that mimic other materials, such as stucco, tile or other textures
• Coating or covering steel siding with products such as board and batton siding, EIFIS, architectural foam and other materials
• Different exterior finishes curbside, while taking advantage of the economy and durability offered by metal cladding on non-curbside portions of the building
• Panels with higher-quality substrates and coating systems that will resist corrosion, chalk and fade over longer periods of time

The following is a case study providing further evidence of post-frame’s durability.

Weathering the Storm – A Case Study

In the wake of hurricanes Katrina and Rita, National Frame Building Association members in the southern coastal states reported how their post-frame buildings stood tall amidst the rubble of other buildings nearby. The reports were no surprise to those familiar with post-frame buildings; their unique design characteristics perform exceptionally well under tremendous wind, snow and seismic loads.

Right after Katrina and Rita, several NFBA members ecstatically reported how their post-frame buildings withstood the historic events. Patricia Askins of Longwood, Fla. emphatically stated, “Of all the hundreds of buildings we’ve built throughout Florida, we’re happy to report absolutely no problems except for minor damage to trim and other small architectural elements on just a few of them.”

Another person proud of post-frame’s performance was Jerry Wagner of Lake Wells, Fla. Wagner and other post-frame builders in Florida and Mississippi described miles and miles of demolished buildings, interrupted by the occasional post-frame building with little or no damage.

Wagner reported that one customer said, “I’m not complaining! My building is the only one left standing for 10 miles around.” There was another building right next to the Wagner erected, but the owner put it up himself. “The building he put up didn’t stand a chance against hurricane-force winds in excess of 100 miles per hour, but our pre-engineered building was fine,” Wagner said. “It highlighted for him the importance of hiring a professional builder who will erect buildings in accordance with building codes and structural engineering requirements appropriate for the area.”

Builder Dale Gay of Chunchula, Ala. noticed some breathtaking sights when he was driving around the countryside to see how buildings his company erected fared the storm. Strikingly, although not completely unexpectedly, he noticed that his buildings elegantly stood out in a barren landscape otherwise dotted by piles of debris – many of which used to be buildings.

Gay described mangled stud-frame houses, twisted metal-framed structures, and a concrete block building that had an entire wall collapse in between stops at various buildings he had erected. He described the scene as comparable to a war zone. Buildings of all types in all directions were leveled; but not his post-frame ones. He began taking photographs to illustrate the point.

Of course, within the path of a hurricane there are few buildings that won’t have some kind of damage. “Almost no building can survive a tornado, and we did see one that we could tell was destroyed by a direct hit because it scoured a path right through the lot,” he said. “But our buildings stood up fine to the hurricane. The 100+ mile per hour winds sucked the windows out of some buildings, and we lost some doors, but none fell down. Other buildings flew apart and the debris hit our buildings, resulting in some superficial damage; but every one of ours was still intact.”

Kevin Lawrence of Tallahassee, Fla., reported their area was hardest hit by the rash of storms that hit the state. “We erected a hangar at an airstrip in the greater Pensacola area,” he said. “There were a whole bunch of hangars there that got demolished. One not more than 12 feet away from one of our hangars was completely leveled to the ground, but our post-frame structure was unharmed.”

“We built one right on the coast in a residential area near Pensacola,” he continued. “They lost 12 houses in that neighborhood, but our building was left unscathed - except for the weather vane. Not one of our buildings suffered major damage.”

Kevin Dunn of Gainesville, Fla., noted: “There was airborne debris damage, but absolutely no major damage on any of our buildings. In fact, many Florida mobile home residents use post-frame buildings as hurricane shelters.”

“We got hit in the eye of Hurricane Katrina with winds up to 175 miles per hour,” reported J. Montague of Biloxi, Mississippi, the owner of a post-frame structure. “My building held up immaculately.”

Challenge: Constructing buildings in the Southern, coastal United States capable of handling the load of hurricane winds.

Solution: Build properly-engineered post-frame structures according to the NFBA Post-Frame Building Design Manual for buildings capable of handling the load of a category five hurricane, such as Katrina.

Result: In the wake of hurricanes Katrina and Rita, many non post-frame structures lay in ruins while properly engineered post-frame buildings remained standing tall.