Building weather resilient structures

Severe weather is happening more often. In 2023, property insurers had their costliest year ever with $92.9 billion in losses.¹ Ryan Michalek, Director of Property Engineering at Nationwide Insurance, says farm buildings often get more damage in bad weather than commercial and residential buildings. The main reasons are:

• Lower design values used for weather in farm buildings
• Not following building standards in farm construction 
• Missing a well-designed continuous load path across building components 

As severe weather becomes more common, it’s clear we need to build stronger farm structures. Following Nationwide’s ABCs of building more weather resilient farm structures can help protect your farm buildings.  

The ABCs of building more weather resilient farm structures

 Agricultural weather load reductions: Avoid using lower load values for farm buildings. Design them to the same standards as residential or commercial buildings. 

Building standard: Make sure construction meets recognized building standards and include this in the construction contract.

Continuous load path: Have a competent designer evaluate every part of the building involved in load transfer. 

Agricultural weather load reductions

Weather loads can vary a lot. For example, snow can be light and fluffy or wet and heavy. To find the right design load for a building, designers use standards like the American Society of Civil Engineers Standard 7 (ASCE 7). This standard provides loading criteria for all types of loads, including weather loads. ASCE 7 sets minimum weather loads through statistical analysis, giving a design value that is unlikely to be exceeded in a given area in any year.  

Farm buildings, according to ASCE 7, can use lower standards (or confidence intervals) compared to residential homes or commercial buildings. This means farm structures are often designed for lower weather loads and can fail more often in severe weather. However, owners can choose higher load criteria than ASCE 7 prescribes. Doing this can make farm buildings as strong as, or even stronger than, a residential home or commercial building in severe weather.  

Many remember the severe damage caused by the August 2020 derecho and its high wind speeds. Nationwide’s BinStrong^SM campaign started after these windstorms to emphasize the importance of using grain bins that can withstand higher wind speeds. BinStrong^SM promotes specifying higher weather loads than the minimum prescribed in the ASCE 7 standard to reduce the risk of damage from severe weather, ensuring better protection for grain storage and financial stability. 

Building standards

Building standards are often missing in rural areas where farm buildings are constructed. This can be due to laws, lack of local building codes, or simply no building code enforcement. Building standards set minimum requirements for structural performance, protecting occupants and contents from undue risk. Without these standards, the requirements for building design and construction are unclear, and performance in severe weather is unpredictable. 

One common issue is the installation of long-span wood trusses. These trusses have a clear span of 60 feet or more and are popular in farm buildings. The International Building Code² requires a licensed engineer to design the lateral restraint system for these trusses to prevent collapse under load. However, this design is often omitted in farm building construction, resulting in a truss system that can only support a fraction of the snow load prescribed by the building code. 

Require all farm construction to meet local building codes and include this in the construction contract. If no local code exists, use the county, state, or a nearby municipality’s building code as your basis for code compliance.  

Continuous load path

Forensic analysis of farm buildings after weather damage often reveals a common issue: the lack of a well-designed continuous load path. A continuous load path ensures that structural loads are transferred from the point of application through every building component until the load is resolved into the foundation. Farm construction projects usually do not have someone responsible for coordinating a continuous load path across all components, leading to failures at the weakest point. 

For example, a metal roof section lifting off a post-frame building during a windstorm often happens because the fastened connection between the purlin and the wood truss was not designed by a competent individual. The truss, roof sheathing, and purlin may have been designed correctly for the wind load, but no one designed the fastener to safely transfer wind loads between components. 

To avoid issues with your farm building’s continuous load path, use a competent building designer responsible for the structural design across the entire building system. 

Additional resources

Nationwide’s BinStrong^SM campaign helps farm and agribusiness owners understand the benefits of building stronger, higher wind-speed rated grain bins. By specifying higher wind loads for farm storage bins, owners can lessen the likelihood that windstorms will affect their ability to store grain. To learn more about BinStrong^SM by Nationwide, visit Nationwide.com/BinStrong.