Matt Oblinsky, PE, Director of Engineering for Deltec Homes
Steve Linton, President for Deltec Homes
The intensity of recent hurricanes such as Dorian, Michael, Irma, and Harvey has increased our awareness of the raw power of the forces of nature. When combined with the measured effects of climate change on our world, and especially on our coast lines, the question of how to build a home that is resilient to these forces is one that will be with us for a long time.
This three-part series will seek to answer a central question: How can we change the way the world builds in hurricane areas? More specifically, we will explore answers to:
- What key factors help keep a home safe in a high wind event?
- What are the most common ways that winds can damage a home?
- How can sustainable features be used in homes to increase their performance before, during, and after a hurricane?
- What measures can be taken to improve the resistance of any home to high winds?
- What should homeowners and families do to prepare for future storms?
The goal of a well-designed home in hurricane areas is to ensure that all forces that hit the home are transferred into the ground while maintaining an unpenetrated home envelope. When designing a resilient home that will be subjected to extreme wind forces, special attention should be given to the common failure mechanisms, such as inadequate roof attachment, wind intrusion, and poor foundation design.
To start, designing a roof system that is best suited for your environment is the first line of defense. A moderate slope roof (approximately a 6:12 pitch), with no gable ends, has been shown to perform the best. A moderate slope roof helps reduce wind pressures acting on the system while allowing for proper waterproofing. Eliminating gable ends removes one of the most susceptible areas during a high wind event. Therefore, the use of a hip style roof will provide a more stable shape that can be equally strong form multiple directions.
The typical roof structure attachment method of an older home, or one that is not located in a high wind area, is simply to nail the roof trusses or rafters into the top of the walls. Newer homes in high-wind areas now use “hurricane straps,” which are metal ties that connect the roof to the walls. Better yet, these hurricane straps can be a “saddle” type, connecting to both sides of the roof member, and can be paired with continuous metal strapping from the roof all the way into the foundation.
A hurricane naturally creates extreme pressures on the outside of a structure. Some people think that by opening a few windows in their home that they can help to equalize these pressures, but in fact, the exact opposite happens. The pressure on the leeward side of the home (the side of the home that the wind is not directly hitting) becomes twice as powerful: the wind outside the home is “sucking” the wall outward, and the wind blowing inside the home is blowing the walls outward. For this reason, it is critical to design a building envelope (the fancy name for what separates indoors from out) that can maintain its integrity during a storm.
There are many factors in designing a strong and continuous building envelope, but some of the basic elements include using impact resistant doors and windows, and/or using shutters or boarding up doors and windows ahead of a storm.
Keeping your home tightly connected to the ground is certainly intuitive, but can be challenging to do. Coastal foundations not only have to transfer wind forces from the house to the ground but also have to resist wave and flood forces, debris impacts, corrosive environments and not be subject to erosion and scour. It is critical to have foundations designed by professionals that can consider all these factors for the location you are building.
Whether building a new home or upgrading an existing one, make sure these critical items have been taken into account and properly designed. Creating homes that stand against some of the strongest forces in nature requires care and precision, and attention to the smallest of details. At the end of the day, we all want safety for our family, our property, and our communities. Building a home the right way, the first time, allows us to leave a legacy for future generations.
For more information on building homes to stand up to hurricanes:
- Home Builder’s Guide to Coastal Construction – Technical Fact Sheet Series
- IBHS Fortified Homes – Hurricane Standards
Matt Oblinsky is a Professional Engineer and has a structural engineering degree from NC State University. He leads Deltec’s engineering team and regularly designs homes for the highest risk hurricane areas. Steve Linton has a structural engineering degree from Cornell University and has been the president of Deltec Homes since 2011.
Deltec Homes is changing the way the world builds, from the status quo to The Deltec Way: where excellence comes first, where homes have a regenerative effect on our planet, and where homes reconnect us with the natural world around us. For over five decades, we have designed homes that stand against nature’s toughest storms. We are committed to building legacy homes that enrich lives and will still be standing for future generations.
Resilient Homes Part Two: Sustainability Before, During, and After a Hurricane
Resilient Homes Part Three: Proactive, Preventative Measures for Your Home
- Protect all openings (windows, doors, esp garage doors)
- Roof tie down (can be retrofitted)
- Continuous load path to foundation
- Elevate home from water – whole other issue
- If designing new, consider shape:
- No gables (hips)
- Square over rectangular, multi-faceted over square
- Wind pressure effects