The Takeaways:
- Thousands of buildings in California share a flaw with many buildings collapsed in Turkey and Syria with the non-ductile concrete that does not have much steel reinforcement and holds up poorly in earthquake conditions.
- While the number of non-ductile concrete buildings in California are alarming, they aren’t nearly as common as they are in Turkey, primarily because such buildings stopped being erected in the United States after a 1971 earthquake in San Fernando.
- Estimates of California non-ductile buildings range between 7,000 to as many as 17,000 buildings in the highest-risk counties.
- Cities in California are actively working to retrofit non-ductile concrete buildings, although one major obstacle is the cost.
- We can learn 7 things from the recent Hurricane Ian in Florida: replacing aged roof covering, a fully sealed roof deck, roof to wall connections, windows rated for high wind pressure and debris, unbraced garage door, elevated structures or foundation and having flood vent.
Two Reports on Building Materials You Should Know
I’ve read two recent pieces that I’d like to share with you. The first is more newsworthy and relevant to California, with a title that says: “Some California buildings share a flaw with the ones that fell like ‘pancakes’ in Turkey quake, but similar devastation is unlikely.”
The second is indirectly relevant, as it talks about ways to protect your home in 2023. It is more directly relevant to Florida, as “experts reveal how hurricane mitigation efforts … have created more resilient homes – and how homeowners can further build upon this in 2023.” You must admit that the title is attractive: Who would not want to learn to make their home stronger?
A NASA article has the following words for California: “There’s an old adage (with several variations) that California has four seasons: earthquake, fire, flood and drought. While Californians happily cede the title of Hurricane Capital of America to U.S. East and Gulf coasters, every once in a while, Mother Nature sends a reminder to Southern Californians that they are not completely immune to the whims of tropical cyclones.”
The commonality behind them however is about how to make your home stronger to resist natural disasters like earthquake or hurricane. Although the latter does not happen frequently, all houses will benefit from the extra strength families can add to their beloved building.
Ways to Make Your House Strong
None of the seven ways of protecting a house is mysterious and perhaps all have been heard of before by most Californian homeowners.
The first way is roof covering or to replace aged roof coverings. It is highly expected that intact roof coverings minimize water intrusion, while aged shingles may become unsealed and more prone to damage by high wind. In Florida the term “aged roof” refers to 7-10 year old, although without hurricane the age of shingles can be longer in California.
The second is roof deck, which refers to the last line of defense for preventing water intrusion if the shingles or roof coverings are displaced in a hurricane of storm. Florida experience says a fully sealed roof deck will help minimize interior damage in future hurricane events.
The third is roof to wall connections, although this one is unlikely to be as important as in Florida, where it shows a roof that does not have a connection that fully wraps around the roof truss and connect to the walls is more likely to be lifted completely off the structure in high winds.
Window is the next item. From Hurricane Ian Floridian found that windows rated for high wind pressure and debris impacts are critical to structure survivability, which limit major interior damage and structural failures in Hurricane Ian.
The fifth is garage doors need to be braced, as unbraced garage door can buckle under high wind pressure allowing the interior of the structure to pressurize, putting the home at risk of a major structural failure.
The sixth is foundation. This time with Ian more than 10 feet of storm was recorded. Elevated structures built to current building codes suffered limited damage while structures built directly on the ground were severely damaged.
The last one is flood vent that can be found in many newer homes on the Southwest Florida coast, which helps mitigate foundation failures due to storm surge. The flood vents allow storm surge to move in and out of the structure without creating excessive pressure on the walls.