When you’re in the residential construction business, you never want to think that the worst could happen. But homeowners and builders in Florida and other coastal areas know only too well the devastation that can result from hurricanes and tropical storms. It’s why local building codes include strict requirements on housing materials to make sure they can withstand extreme weather.
For decades, fiber cement siding has been a go-to choice for Floridians and other coastal homeowners. Nichiha is proud to provide a variety of fiber cement products that meet and exceed wind load code requirements, along with being low-maintenance, fire-resistant and offering a huge variety of sizes and textures to meet your design vision.
Nichiha is also approved by the Florida Department of Business and Professional Regulation. To see the testing data, visit www.floridabuilding.org and enter 12098 in the FL # field.
But ensuring the right siding product is chosen and that it will stand up to severe weather is not a one-size-fits-all solution. Many factors go into choosing the right siding, based on the design of the home, its location and even how the fiber cement siding is installed.
Factors affecting wind load ratings include:
When choosing exterior home siding in coastal areas affected by high winds, size matters, particularly with lap siding where panels overlap slightly. During high winds and extreme weather, wind can slip under these points of overlap and create strain, using the panels like a lever to lift them off the home.
The smaller the panel profile, the higher the wind load rating. For example, under the conditions where a NichiProducts 9 ¼” siding would have a maximum wind load rating of 34 pounds per square foot (PSF), the same product in 8 ¼” size has a rating of 46 PSF. These ratings continue to increase as the width of the profile decreases.
For those who want to be sure the new siding meets code requirements, choosing a narrower profile will bring added peace of mind.
Lap siding is most commonly fastened using one of two approaches: either blind nailing or face nailing.
In blind nailing, siding is nailed at the top of the panel, with the next panel installed with a 1 ¼” overlap. This overlap covers the line of nails below.
In face nailing, both boards are nailed together into the home’s studs, so they wind up being fastened at both the top and bottom of the panel. The panels still overlap in the same way they would in a blind nail fastening.
Historically, blind nailing is considered to be the more aesthetically appealing; however, with the panels only fastened at the top and not at the bottom as they are with face nailing, there is added risk in high winds.
Panels attached to a home with blind nailing have a lower wind load rating than those attached with face nailing. Nichiha’s products still meet code for most parts of Florida, even using blind nailing, but for those who are particularly concerned could consider face nailing the siding for extra reassurance.
For those worried about balancing aesthetics and wind resistance, one potential compromise is to blind nail siding on the lowest story of the home, where it is most often seen by family and visitors, while face nailing upper stories, where wind load requirements are higher and where the nail line is less likely to be seen.
You should also consider the type of nail used when blind nailing. Roofing nails are the best option with blind nailing because they have a larger head than a siding nail. The size of the nail head governs what's called fastener pull-through of the siding product. Larger nail heads spread the forces more while smaller ones concentrate them. It’s similar to the difference between snowshoes versus just boots: You should choose the right product for the environment.
Wind load code requirements vary geographically because wind speeds vary. While parts of south Florida can often expect the highest winds during hurricane season, cities farther north and inland are more protected, and therefore, their code ratings are based on lower wind speeds.
When reviewing siding and wind load ratings, make sure city-specific requirements that take local wind speeds into consideration are looked at. The difference in 10 miles an hour of wind speed may not feel very different in the middle of the hurricane, but it can mean the difference between choosing a wider or narrower siding profile, or using blind or face nailing.
Wind load codes are also defined based on building height. The taller the building, the greater risk of damage during severe weather. Minimum siding wind load ratings change depending on where they are installed on a home.
In other words, the rating required for siding installed on the lowest floor of a home is less than the minimum required rating at thirty or sixty feet above grade.
When building a multi-story home or multi-residential building, address the issue of height when selecting exterior house panels by either choosing the profile that is rated for the tallest part of the building or by changing the fasteners on upper floors.
Another alternative, for those who are feeling creative, is to work with more than one siding profile. Many current design trends mix and match siding profiles from one floor to the next; this is not only an aesthetically-appealing way to create some visual interest but also to ensure the entire building is code-compliant, by choosing smaller profiles for upper floors and wider for the bottom.
One of the most critical, but often least easily quantified, factors that goes into setting the wind load code requirement for siding is the exposure factor. It’s fairly easy to visualize heavy winds blowing against a home and putting a strain on the siding. What may be harder to imagine is how the surrounding area plays a factor, too.
Topography, both natural and constructed, plays a large role in setting wind load code ratings. Buildings are typically said to be in B, C or D exposure areas.
In short, choosing wind load code-compliant exterior house siding is dependent on all the factors above. How big a siding profile should the home have? Are you comfortable with face nailing for extra security? What part of the state is the home located in and what are the rated wind speeds for that area? How tall is the home? What is the exposure rating?
All NichiBoard sizes up to and including 9 ¼” are wind load-compliant in Orlando, for example, to heights up to thirty feet, using blind nailing fasteners. For taller buildings, consider face nailing or using a narrower profile. Or, for homes in other parts of Florida or in other coastal areas, contact Nichiha to help pick the right NichiProduct for the location’s specific wind load code requirements.