This post originally appeared on the Green Building Advisor website. www.greenbuildingadvisor.com
In 2013, a thunderstorm with high winds took a large section of shingles off the roof of the home I owned at the time leaving the roof deck exposed to the heavy rainfall that followed. For more than a half hour I stood by helplessly watching rainwater enter the home, soaking the attic insulation and dripping down through every light fixture in the affected areas. Fortunately, the shingles and a couple pieces of siding were all that were affected by the winds, the public forest behind the home was not so lucky, thousands of trees were uprooted. The clean-up and repair along with dealing with the insurance company took weeks, but eventually the home was made whole again. 
My experience with roof damage during a storm is not unique; thousands of people experience the damage that can occur when winds tear off sections of their shingles every year. According to the Insurance Institute for Business and Home Safety (IBHS), roof-related damage is responsible for an estimated 70-90% of the total insured residential catastrophic losses.
Recently I was asked to help consult on a new home in my area. The homeowner wanted to build above code and asked if I would help the builder and designer with ideas and products that would best fit the homeowner’s budget and goals. One of the conversations we had was on durability. In the back of my mind was my experience with wind damage. I had been looking into a program called FORTIFIED Home and thought this program might be a good fit for this homeowner.
The home is being constructed on the northeast corner of Minnesota’s fourth largest lake, the 67,000-acre Lake Winnibigoshish. The home faces southwest with an 11-mile expanse of open water. As you can imagine, the wind can blow quite hard at times. With the potential of future storms causing roof damage, the FORTIFIED Roof model was worked into the build.
What is FORTIFIED?
The FORTIFIED Roof program was developed by IBHS to minimize the damage to a home that can occur when severe weather hits. The program is really pretty simple, improve the roof sheathing’s attachment to the roof framing, make it harder for the wind to remove the finished roofing material, lessen water’s ability to enter the home should the roofing material be blown off, and install a roofing material that is more resistant to hail damage. None of these improvements adds substantial cost to the building and may even save money in the long run by reducing the cost of insuring the home. There are different FORIFIED levels for residential construction, FORIFIED Roof along with the FORTIFIED Silver and Gold certifications. The silver and gold programs add requirements to the entire home, such as enhanced window and door packages and engineered building component connections. These higher levels of protection are usually chosen in very high wind and hurricane prone areas. The programs can be applied to both new and existing structures.
Requirements for the FORIFIED Roof program.
Because the project I’m working on is only concerned with high straight-line winds, and not hurricanes, we only applied the FORIFIED Roof requirements to the project.
The first requirement is minimum thickness and attachment of the roof sheathing. The program requires a minimum of 3/8” sheathing when applying over a 16” on center roof framing, or 7/16” sheathing when applying over a 24” on center framing. The sheathing must be attached using a 0.113” diameter, 2 3/8” ring shank nail in most cases. The nailing pattern is either 4” or 6” depending on criteria and program. For our project, the building contractor chose to use 5/8” thick OSB roof sheathing over the 24” on center rafters, we ended up using Huber’s Zip System sheathing.
The next requirement is sealing the roof sheathing, this can be done by a couple methods. The first is to use a self-adhering membrane over the entire roof. Depending on your climate, type of self-adhered membrane and choice of finished roofing material, this may or may not be a good idea. The second option is to use a tape to seal all the sheathing seams. In our case, we are in climate zone 7, a heavy snow area with the potential for ice dams. Codes require us to install ice and water barrier (a self-adhered membrane) at least two feet beyond the exterior wall plane. We taped all the seams in the Zip sheathing using Zip Tape, then applied Zip’s peel and stick underlayment membrane per our local codes. This not only meets the requirements for the FORTIFIED Roof program, but it also qualifies for Huber’s Leak Free Guarantee. ZIP-System-Roof-Leak-Free-Limited-Warranty-SEC.pdf (huberwood.com)
If you are using an underlayment product, (which would be required if not using a coated OSB product such as the Huber Zip System sheathing panels), the underlayment must meet the specifications of ASTM D226 Type II (#30 felt or equivalent). The underlayment is fastened using an annular-ring or deformed-shank roofing nail with a minimum 1-inch diameter cap. The type of cap depends on the wind design speed, an all-metal cap would be required in hurricane prone areas. The fastener spacing is required to be 6-inches along all edges and 12-inches in both the horizontal and vertical axis in the field. The selection of the finished roofing material may alter these requirements. Refer to the FORTIFIED Home Standard 2020 for specific requirements.
26-gauge or heavier steel drip edge that extends a minimum of 2-inches onto the roof deck sheathing and a minimum drip edge drop flange covering at least ½-inch below the bottom of the sheathing. The installation of the drip edge is a little different than how I was taught. We always installed the drip edge over the underlayment on the rake of the roof, but under the underlayment at the eave. The FORTIFIED Roof standard wants the drip edge over the underlayment on all edges. The drip edge is fastened 12-inch on the center for high wind locations and 4-inch on center for hurricane prone areas. There are other variations of the requirements depending on roofing material and roof pitch.
The last requirement is with the finished roof materials. I’m only covering the basics on the asphalt shingle, there are alternative requirements for clay and concrete tile, metal shingles and panels, along with other steep and low slope options. Shingles must meet the requirements of ASTM D3161 or ASTM D7158 and installed per the manufacturer’s instructions for high wind zones. Starter strips are required at both the eave and rake, there are options for both (one of the rake options uses flashing cement instead of a starter strip). There are also requirements for open and closed valleys.
One Drawback
Overall, I think the Fortified program is a good idea, especially in hurricane and high wind locations. I don’t know about you, but I’ve noticed some of the effects of climate change in my local environment, making this program even more valuable. One difficulty I did notice is a lack of evaluators in my area to certify the installation. Using the “Find a Professional” tab on the FORTIFIED website showed the nearest evaluator in Mobile, Alabama, a bit of a commute to Northern Minnesota. There may be an opportunity for real estate inspectors to expand their business and become certified in the FORTIFIED Home programs.
This is just the tip of the iceberg. There are many more details, along with drawings showing the requirements to achieve the FORTIFIED certification on their website. FORTIFIED Home – Homepage – FORTIFIED – A Program of IBHS
For more information on the Huber Zip Systems used for the Winnie Pretty Good House, use the links below:
https://www.huberwood.com/zip-system/roof-sheathing
https://www.huberwood.com/zip-system/peel-and-stick-underlayment