Can the Size/Weight of a House Help It Withstand Wind-Based Natural Disasters Like Tornadoes and Hurricanes?

When considering the vulnerability of houses to wind-based natural disasters such as tornadoes and hurricanes, the size and weight of a house might not be the most critical factors. My insights, based on years of reading technical reports and studies on wind engineering, suggest that the shape, materials, and design of a house play a much more significant role in wind resistance.

Introduction to Wind Resistance and House Design

From an engineering perspective, it is crucial to understand that wind resistance is influenced by multiple factors. While size and weight do play a role, they are often overemphasized. The key to designing a resilient house lies in understanding wind dynamics and how they interact with different building shapes and materials.

The Role of Shape

One of the most important factors in wind resistance is the shape of the house. A large, rectangular, two-story wood-frame house with dimensions 50 ft long and 20 ft wide may experience less wind-lift force than a smaller, single-story concrete dome or a wood-frame Deltec home with the same area. This is because a larger structure has a larger surface area, which can increase the points of force entry, making it more susceptible to wind uplift.

Furthermore, the orientation of the house can significantly impact its wind resistance. Rotating a two-story house so that the shorter side faces the wind reduces the force acting on the structure. This concept underscores the importance of design that treats all sides equally to ensure better overall wind resistance.

The Importance of Material Strength

The materials used in constructing a house also play a crucial role in its wind resistance. Highly reinforced concrete offers excellent strength and stability compared to stick-built homes or mobile homes. An example of this is a huge building constructed with 1970s mobile home engineering, which may be more susceptible to damage due to its lighter materials and potentially less robust construction compared to a smaller mobile home.

A Comprehensive View of Wind Resistance

It is important to note that buildings are seldom completely 'blown away' by wind. In most cases, the wind gradually disassembles the structure piece by piece. High winds do not move the entire structure but rather blow apart individual components. This means that a larger house, while it may take longer to be structurally compromised, also exposes a higher profile and may lose more pieces at once.

The critical aspects in designing a house for wind resistance include:

Shape: The aerodynamics of the house's design can significantly influence its wind resistance. Aerodynamics: The complex aerodynamics of various elements, such as eddies behind a chimney and the force on eaves, can affect a house's ability to withstand wind. Surface Smoothness: smoother surface materials are less prone to complex aerodynamic forces. Material Strength: both the raw strength of the materials used and the strength of fasteners. Strategic Use of Materials and Fasteners: proper use of strong materials and fasteners in strategic places can enhance the overall strength and stability of the structure.

Examples of Wind Resistance in House Design

For example, in construction, the way the roofing materials are fastened can greatly affect wind resistance. A stick-frame house with roofing plywood screwed to the rafters, even if the roof is larger, may perform better than one where the plywood is conventionally nailed to the rafters. Additionally, a hip roof covering the same square house footprint can fare better than a gable roof, as there are more points where wind can get under the eaves, making the hip roof more resistant to wind forces.

Overall, while the size and weight of a house are not negligible factors, they are overshadowed by the shape, materials, and strategic design elements that can significantly enhance a house's wind resistance. Understanding and applying these principles in house construction can greatly improve the safety and resilience of structures in the face of wind-based natural disasters.