No Hurricane Straps? No Worries.

Older homes often lack the requisite metal tie downs to keep roofs on during a hurricane. Adding them in retrofit is more affordable than you think.

In storm-prone areas such as Florida, an insurance cost crisis is raging. But one of the worst “amplifiers” of insurance costs for home is part of what’s called the “wind mitigation” features.

Both lenders and would-be insurers insist on a wind mit survey, along with what’s called a ‘four point” survey (not discussed in this article), before they quote your annual price. On a $350,000 home, the annual discount on insurance for a house with clips can run as high as 50 percent.

Nails matter. Under some codes, the number of nails in each strap affect whether it meets wind mit requirements. Some companies such as Third Nail will go in and add nails after the fact for a modest fee. Image: Third Nail

From Worst to Best Practices

What insurers hate to see are roof rafters toenailed to framing top plates without straps or hangers. They’re looking for a strap on each rafter that ties the roof frame into the vertical studs of the wall (for a wood home). For concrete block homes, the principle is the same. Proper mitigation calls for galvanized straps embedded in concrete at the top of the block wall, then nailed properly to the rafters.

The language of clips and straps can be confusing. And just because a home has clips doesn’t mean it automatically meets building codes. For example, Florida homes after 2002 need to have the right number of nails (at least three) in each clip, or else the roof is still considered “toe nailed” to the structure.

Simpson Strong-Tie makes about 20 different types of hurricane tie downs and clips.

Before you retrofit, you might want to review this detailed article about clips and nailing, penned by the insurance industry. Get it right, so you get the discount. The easiest way to actually add new straps to a roof is to open up the soffits and attach new straps or clips. For wood frames, the straps are simply nailed on. For concrete block or monolithic concrete walls, special tapping screws may need to be used.

Caveat: Nails Versus Screws

Keep in mind that in general, galvanized nails have more shear strength than most screws. A typical 16d (3.5-inch) nail has a higher shear strength per unit of material (usually around 3,000 pounds) than most screws. An exterior decking screw, for example, typically has a shear strength between 1500 and 2500 lbs., although it offers greater resistance to being pulled out. Check local building codes, because it’s likely that they mandate nails over screws for hurricane straps or clips.

One gray area with regard to nails and screws is what happens over the lifespan of a home. A few years back, I reviewed some research on long-term fastener strength. Building experts found that as nails corroded, they actually gained more holding power in wood. On the flip side, one would have to assume that they lost some shear strength, as their diameter decreased. More research is needed on how straps and clips perform over time, as fasteners age. Are they as effective 20 years in as they are when installed?

What’s the Bottom Line?

Upgrading the wind mitigation for a 2,000 square foot home in Florida can typically be done for $1,500 bucks or less, accomplished in a day or two. But it can save up to $3,000 per year, every year, that’s a very reasonable 6 month return on investment.

Several retrofit companies offer these services in Florida, with more popping up recently. If I were a realtor, I’d get myself well versed on these upgrades, and include that cost in seller concessions when helping a buyer purchase an existing home.

A little known aspect of homeowner insurance, according to floridadisaster.org, is that discounts can “stack” as high as 88 percent of the total cost of the policy. It’s informative to read through the typical discounts for various construction details. A building with a reinforced concrete roof deck, for an instance gets an 82 percent discount on the wind portion of hurricane insurance in Florida.

Surging Costs. With Florida leading the way, homeowner insurance is spiking in many U.S. States. Discounts for resilient construction soften the blow. Image: National Association of Realtors