How to Design a Coastal Home to Survive Hurricanes
When starting to design a home in a coastal windstorm location, a holistic design approach must be used. There is no single methodology or building product that will create a resilient structure capable of withstanding the high winds, heavy rains, and potential storm surge of a hurricane. There are three distinct areas that need to be evaluated. First is choosing the right team of building professionals that have the expertise and knowledge to design and build in a windstorm area. Second is the specific design criteria that will contribute to the building’s durability. Lastly are the materials that should be selected for their performance in windstorm conditions.
Choosing an architect or designer who has experience with code requirements and building practices in a windstorm area is critical. These are the people who will be able to help guide the project’s design to meet the needs of the owner and the relevant building codes. A windstorm engineer is not only required* to meet code and be insurable, but also ensures that the building will be constructed to withstand the forces imparted on a home during a hurricane or tropical storm. Picking an experienced coastal homebuilder is the last part of the team of building professionals. A knowledgeable builder will be able to price the home correctly and build it to standards set forth by code, the designer, and the engineer.
There are multiple criteria that should be reviewed and implemented when designing a home in a coastal area, including:
Site selection: Utilizing wind breaks from other structures and trees can lessen the wind forces on the building during storms while being mindful of the potential for trees and other materials to become airborne and cause damage to the structure.
Finished floor elevation: Designing the house on piles or significantly raising the elevation of the site can make the difference between storm surge flooding the structure or not.
Keeping walls shorter: Design the home to have shorter overall heights of walls on single stories and less floor-to-floor heights on multi-storied buildings. This will lessen the overall wind pressure on the structure.
Lower roof pitches: A low profile roof will have less wind pressure imparted to the roof and consequently to the rest of the structure.
Avoiding large open roof areas: Try to avoid extended eaves and deep roofed porches, as the high winds put upload pressure on these areas which can cause significant damage to the roof.
No ridge vents: While there are some benefits associated with having ridge vents, they become open water drains into homes when horizontal and wind-driven rain is pushed up a roof.
There are specific building materials that should be used when building in coastal windstorm areas. Each of these categories has multiple choices of materials that have been tested to withstand the forces of windstorm events.
The design of the roof is critical to resisting the forces of hurricanes, but the selection of roofing materials is equally important. A fully-adhered ice and water shield should be applied to the roof sheathing, replacing conventional mechanically fastened felt paper. If the roofing material becomes compromised, this more resilient barrier can keep rain from entering the structure. There are many different roof finishes, but close attention should be paid to the details. For composition shingles, it is important to follow installation best practices in windstorm areas, and to use materials with the proper wind classification. If a metal roof is chosen, the end cap detail needs extra consideration. If a metal roof is damaged by wind, often times, entire sections will be peeled off the roof.
The load bearing wall assembly is an essential part of the design. Choosing the right materials for the walls should be one of the first decisions made when designing a house on the coast. Robust, resilient concrete walls are the best performing system in high wind events. Not only do the walls withstand the wind forces, but they also defend the structure against wind-borne debris. The Bautex Wall System is a proven insulated concrete wall system designed for coastal structures. Tested to FEMA 320⁄361 and ICC 500 requirements for windstorm, Bautex walls are easily installed and are highly energy efficient. With the Bautex wall there is no wood or exposed steel that are susceptible to rot or rust, and, ultimately, to structural failure during a windstorm event after years of exposure to salty and humid marine air.
Windows and Doors
Specifying impact resistant and tested windows and doors is a must-do. If a house is built with the most durable walls and roof but has weak windows or doors, the building can become compromised in a hurricane or tropical storm with high winds and flying debris. Hurricane windows are worth the investment when compared to the costly water damage that can occur during these types of storms.
Unless connected to a more substantial concrete wall system, cavity wall finishes such as brick, stone, traditional stucco on metal lath, or rain screens should be avoided when building a house on the coast. Wind pressures can get behind these types of cladding materials and cause them to be pulled off the building. On wood sheathed buildings, this leaves the shear reinforcing system (the sheathing) exposed directly to the windstorm forces which can lead to complete structural failure of the building. Choose direct applied and tested finishes that perform better in high wind storms.
There is no exclusive solution to designing a resilient costal home. The design must be looked at holistically. The right design professionals are a great first step, but ensuring critical design principles and choosing the best materials are also vitally important. Only when all of these items are done in conjunction can a durable and safe home be designed and built in high windstorm areas.
For more information about building a resilient home in a coastal area, go to bautexsystems.com or send us an email.
*In order to be eligible for coverage through the Texas Windstorm Insurance Association (TWIA), Texas Insurance Code Chapter 2210 states that any building constructed, altered, remodeled, enlarged, repaired, or added to on or after January 1, 1988 must have a Certificate of Compliance (WPI-8 or WPI-8-C) to certify that the structure meets the windstorm building code requirements. Without a Certificate of Compliance, TWIA lacks evidence that the structure conforms to the applicable building code, and the structure may be considered uninsurable and ineligible for coverage with TWIA.