Your roof. Excluding rafters, this two-inch layer is meant to protect the entire structure from the elements. That includes high and low temperatures, rain, ultraviolet radiation, snow, ice, and hailstones. It’s also required to stand up to hurricanes, tornadoes, microbursts, and blizzards.
Which means, your roof is the most important element of your home in a high wind event. What are you doing to protect it?
In this post, we explore why roofs fail, the best building practices for a high-performance roof, and how seaming tape can help.
Why Roofs Fail
According to the Federal Emergency Management Agency (FEMA), roof systems typically fail due to wind. Gusts as low as 30 mph can lift the edge of an aging asphalt. Winds more than 50 mph can damage roof tiles. And anything greater than 60 mph can tear roof coverings from roof decks and can separate roof decks from framing. Roofs can also fail if punctured by wind-borne debris.
So here’s the bad news: the typical roof built in America hasn’t changed much in 85 years. Roof sheathing (OSB or plywood) + roof underlayment (mostly asphalt impregnated felt) + a roof finish (mostly asphalt shingles). When constructing the roof, a ⅛” gap is left around each 4’x8’ roof sheathing to allow natural expansion and contraction of the wood. The sheathing and designed expansion gaps are then covered in an underlayment with any necessary flashing integrated and then finally the finish is nailed on. Viola, a water tight assembly … right?
Wrong. Shingles and felt paper can be ripped away from roofs built like this, which happens to be a majority of homes in the U.S. Just watch:
Tile shingles aren’t any better. Water intrusion on tile roofs can occur at wind speeds as low as 50 mph. So, whether its asphalt or tile, roof damage leaves your home susceptible to bulk water intrusion at all the sheathing gaps. In a 2,000 sq.ft. home, that’s like a 5-foot hole leaking water like a sieve.
According to the Insurance Institute for Business & Home Safety(r) (IBHS), weather events such as windstorms, rain, fire, hail, ice, and snow accounted for an average of $21.8 billion dollars in insured property losses annually from 2003–2012. This damage can be further intensified by weathering and pest damage.
It can’t be emphasized enough — your roof is the most important element of your home in a high wind event, be it microburst, tornado, hurricane, or something else altogether.
Properly designed, installed, seamed, sealed, and maintained roofs are the best line of defense in significantly reducing or preventing damage to buildings and their contents from natural hazards.
Building a Better Roof
So, how do you begin building a better roof? With a better building code, of course.
Roof coverings are addressed in Chapter 15 of the IBC and Chapter 9 of the IRC. Both codes provide requirements for roof coverings commonly used on high-sloped roofs (such as asphalt shingles, clay and concrete tile, wood shakes and shingles, and metal roofing) and for roof coverings typically used for low-slope applications (such as built-up roofing, thermoset single-ply roofing, thermoplastic single-ply roofing, sprayed polyurethane foam roofing, and liquid-applied coatings). Both codes also contain requirements for roof decks, underlayment, flashing, structural performance, and materials and testing criteria.
Since 2012, building codes have increasingly provided increasingly stringent requirements for the design and installation of roof coverings in high-wind areas, i.e., where the basic wind speed is 110 mph or greater.
But make no mistake, the entire continental United States is in a high wind, tornado, and hail, or hurricane risk zone.
Designers and builders can choose from a variety of features to help minimize losses from high winds. The choice of features will depend on the severity and type of local wind events. According to Building America(SM), measures are available to fortify all typical construction types, including concrete, masonry, wood frame, and structural insulated panels. Features may include walls and wall covering; roof sheathing and coverings; doors, garage doors, windows, and skylights; and soffit and overhang design. Structural strapping and bracing help to fortify framing. And, of keen interest to us, is the fact that IBHS strongly recommends sealing the roof deck for all roof cover types.
Indeed, the IBHS FORTIFIED Home™ program addresses effective methods to improve roof deck performance in high wind and rain applications. The program has recently been adopted by the Connecticut Department of Administrative Services into new code literature. Alabama and Florida have already mandated the sealing the roof deck seams. Additionally, some insurance companies are offering discounts on homeowner insurance premiums for taking proactive steps when it comes to building stronger roofs.
Tests at the IBHS Research Center have demonstrated that some code-compliant roofing felts may blow off in high wind events. While the roofing industry has referred historically to roofing felt as a suitable backup to reduce roof leaks, IBHS does not consider the use of typical felt underlayments the protective equivalent of a sealed roof deck. IBHS defines a properly sealed roof deck as one where the seams or gaps between pieces of decking are sealed, so that water cannot flow into the attic if the roof cover is lost. The bonding or attachment of the material used to seal the seams to the roof deck materials also must be strong enough to stay in place if the roof cover blows off.
Best Practices for Sealing the Roof Deck
The FORTIFIED Home roof sealing protocol established three options for creating a properly sealed roof deck.
- Install a 4-in. to 6-in. wide “peel and stick” tape over all plywood and/or OSB roof panel seams and then cover the deck with a 30-pound felt underlayment. Apply the “peel and stick” tape directly to the roof deck to seal the horizontal and vertical joints between the roof sheathing panels. Next, apply 30# ASTM D226 Type II or ASTM D4869 Type IV underlayment over the entire roof deck. (ASTM is a nationally recognized organization that publishes technical standards for the performance of a wide range of materials and products, including the wind resistance of asphalt shingles.) Attach the underlayment using an annular ring or deformed shank roofing fasteners, with minimum 1-in. diameter caps at no more than 6 in. on center spacing, along all laps and at 12 in. on center in the field.
- Install a reinforced, high tear strength synthetic underlayment with all vertical and horizontal seams taped. Taped seams on the coated roof sheathing improve a home’s resistance to damage from high winds. This underlayment should have an International Code Council (ICC) approval as an alternate to ASTM D226 Type II or ASTM D4869 Type IV underlayment. The synthetic underlayment must have a minimum tear strength of 20 pounds per ASTM D1970 or ASTM D4533. The underlayment should be attached using an annular ring or deformed shank roofing fasteners, with minimum 1-in. diameter caps at no more than 6-in. on center spacing along all laps and at 12-in. on center in the field. Vertical and horizontal seams of the synthetic underlayment should be sealed with a compatible adhesive or tape.
- Install a “peel and stick” membrane over the entire roof deck. Cover the entire roof deck with self-adhering polymer modified bitumen membrane meeting ASTM D1970 standards. Most shingle manufacturers warn that attic ventilation must be good if these products are used because moisture in the attic cannot evaporate through such membranes. Roofers are also finding that shingles can bond with many of these membranes. To prevent the “peel and stick” membrane from adhering to the shingles, it should be covered with a “bond break,” such as 15# ASTM D226, Type I-compliant underlayment. This “bond break” underlayment only needs to be fastened sufficiently to keep it on the roof surface and provide safety to the roofers until the shingles are applied.
Looking for more best practices, trends, and code information? Try these five resources:
- Read the FORTIFIED Hurricane codes and standards.
- “Designing and Building Hurricane Resistant Homes,” by William Zoeller.
- FEMA’s Coastal Building Guide provides guidance on improving the performance of roof systems by augmenting underlayment installations, specifically Fact Sheet No. 19.
- Mark Zehnal, IBHS Senior Roofing Specialist.
- IBHS Roofing guide
Your Ally in the Storm: Tape
Obviously, ECHOtape is a big proponent of sealing roof gaps, and for good reason. According to insurance data comparing a roof with its sheathing seams taped vs. a standard roof with no tape, potential repairs differ significantly in high wind scenarios. The sealed seam roof may cost about $5,000 to repair with almost all of the cost to repair the roof. The damage to the house with no roof seaming tape is three times that amount, $15,000, because it includes repairing interior water damage done to the interior of the home. And that figure does NOT include the cost associated with homeowners having to stay elsewhere why repairs are made.
So as a homeowner, there are three key benefits of a roof sealed with seam tape which doesn’t leak during a high wind/rain event:
- First, the interior stays dry, which means the family doesn’t have to relocate during repairs.
- Second, if repairs are needed, they are more likely to be aesthetic roof repairs.
- Third, your insurance company may give you a discount on annual insurance premiums but you need to have the work verified by a third-party FORTIFIED evaluator.
Next-generation seaming tapes can provide the superior performance needed for storms and severe weather. Formulated with a proprietary cold weather adhesive, the best seaming tapes are engineered to adhere to a wide range of building materials and surfaces including house wrap, exterior, and rigid insulation, sheathing, vapor barriers, and a variety of underlayments. Seaming tapes made from advanced polyester backing are extremely strong and easy to apply.
Characteristics to look for:
- Tape is hand tearable and easy to use in the field
- Strong and durable holding power
- Excellent cold temperature adhesion to -4°F
- Minimum 90 day UV resistance
- Instant tack on a wide variety of materials that strengthen over time
- Made from an advanced polyester film (PET)
- Water and moisture resistant
- Good conformability to irregular surfaces
- Colors allow for easy inspection
Sooner rather than later, sealing the roof deck seams will be standard practice in high wind prone areas. Why wait for code to force your hand if you can both do good and make money? Take a look at your options for seaming tape.