Why does masonry perform so much better than other light frame products during high-wind events, such as hurricanes and tornadoes?
Long time South Florida residents who have weathered a severe hurricane often express a heartfelt thankfulness that they were in a concrete masonry structure. Structures built of many lesser products have weathered hurricanes but block homes provide the secure comfort of rock solid construction. This is not just antidotal – its common sense. After reading this article perhaps you will have a better understanding of concrete masonry’s built in strength.
It’s all about the “safety factor”. Simply stated the “safety factor” is the difference between what engineers expect will be the largest wind load a structure will ever be exposed to --- and the wind load that they calculate would rip the structure apart. Structural engineers always like a good safety factor – usually around 3 times or 300%. Poor construction and material deficiencies erode safety factors but if you have sufficient safety factor there is some room for error.
Understanding Wood Frame Connection Problems
Wood frame residential structures have performed poorly in every wind event I have had the opportunity to do wind damage assessment on. The problem is not in the wood itself but in the connectors. A tree branch can be very strong – but if you saw it off you will have a real problem on your hands to nail it back on to its original strength.
The lumber industry is extremely sophisticated in their design procedures. Nails and connections are assigned industry accepted load carrying capacities and safety factors based on extensive testing. All of this is proper engineering. There is, however, a number of factors which explain why Hurricane Irma left dozens of modern wood structures in ruins and zero concrete masonry structures in ruins.
- Product Weight and Stability
- Natural Safety Factors in Design
- Complexity in Design
- Complexity in Connections