Continuous Load Path
A strong continuous load path ties a home together—from the roof, through the walls, and down to the foundation, so wind forces are transferred safely into the ground. Without it, wind forces search for weak links. When they find one, failure can cascade through the structure.
This load path is the structural backbone of the IBHS construction approach for its FORTIFIED Home™–High Wind Gold designation. Alongside other requirements—such as a sealed roof deck and reinforced porches, carports, and wind-rated garage doors—the continuous load path is what helps keep the entire home intact under high wind pressure.
Research
In 2017, to advance understanding of how wind affects residential structures, IBHS conducted controlled wind experiments on a full-scale home at the Research Center. One was engineered with a reinforced continuous load path including other FORTIFIED Home™–High Wind Gold components (Science House), while the second lacked these reinforcements to represent a typical home (Demonstration House). Testing the two homes under identical wind conditions provided powerful insights into building vulnerabilities and the proven benefits of stronger construction.
Science House
The first home, the Science House was a full-scale, two-car-garage structure typical of those found in the central U.S. but built with one key enhancement: a strong continuous load path that meets FORTIFIED Home™–High Wind Gold standards. Fully instrumented with sensors, it allowed IBHS to measure wind pressures, structural loads, and any resulting deformation throughout the entire building.
Researchers subjected the home to a wide range of controlled wind conditions, including varying wind directions and speeds, different stages of construction, multiple levels of wall anchorage, and tests with intentionally breached windows and doors. These tests showed how wind forces interact with a structure, how failures begin, and revealed how simple actions such as closing interior doors can reduce internal pressure and improve roof performance.
Testing on the Science House:
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- Validated the benefits of a strong continuous load path.
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- Identified the minimum reinforcements needed to meaningfully and affordably improve durability.
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- Demonstrated how a continuous load path transfers wind forces safely through the structure and into the foundation.
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- Generated a precise benchmark dataset to inform engineers, builders, and code developers.
This dataset includes time-based wind speeds and gusts, wind pressures across the structure, and complete load paths from the roof to trusses, walls, and foundation anchor bolts. These measurements now help guide building codes, technical standards, and future FORTIFIED recommendations.
After the science house testing was complete, IBHS removed the continuous load path components and exposed the home to severe thunderstorm–level winds. Without reinforced connections, the house failed at just over 100 mph, mirroring real-world damage in EF-0 to EF-1 tornadoes and straight-line wind events. The outcome highlighted how typical construction can fail in moderate wind events and how stronger, science-based building practices can greatly reduce these losses.
Demonstration
The second structure, the Demonstration House, was built to represent a typical existing home in the middle of the U.S., illustrating wind performance of standard construction. Unlike the Science House, it lacked a continuous load path, contained no instrumentation, and was fully furnished to reflect a real family environment.
Subjected to the same high wind conditions as the Science House, the home performed as expected: without reinforced connections to transfer loads through the structure, it failed under high winds. The resulting damage mirrored what commonly occurs during severe thunderstorms, straight-line windstorms, and lower-end tornadoes (EF-0 to EF-1) across the central U.S.
These events occur frequently and cause billions of dollars in insured losses each year. The Demonstration House failure vividly illustrates the vulnerability of typical homes and how much of this damage can be prevented using stronger, science-based construction methods validated through IBHS research.
