Opinions vary regarding the best roofing surface materials for hurricane protection. Other factors, such as energy efficiency, are also considerations. All types of roofing materials are rated by United Laboratories for 4 levels of strength: (ClassD=90mph, ClassF=110mph, ClassG=120mph, ClassH=150mph). Many factors affect the actual performance on any particular structure. Roofing material choices are described below, but roof structure and underlayment should be considered first. When re-roofing, it is strongly recommended to remove the entire existing roof to the decking to check/upgrade the roof structure and to install a proper underlayment (base layer).
Roof failures are the largest category in hurricane loss, both in repair of the roof itself and in the wind and water damage caused by the failed roof. Regardless of the roof surface used, the most important aspect of the roof in its structural frame and sheathing. Wind driven uplift is the roof’s biggest threat. Much can be detailed here, but addressing the following is essential:
- Structural walls need to be sufficiently strong enough to secure roof supports (tie or bond beam is best)
- Roof trusses need to be adequately built and attached to walls (double strapping is best)
- Roof deck needs to be strong & properly fastened (min. 5/8″ plywood & 8D ring-shanked nails spaced 6″ max)
- Hip roofs are safer than gabled (if gabled, need to reinforce with bracing and cover vents during storms)
- All openings need adequate protection to impede uplift (doors, garage doors, windows, soffit vents)
Underlayment (base layer):
Per the new coastal building codes, the roof’s base layer requires it to serve as an enhanced secondary water barrier to help protect the roof if the surface material blows off. Local codes vary on methods.
- All require a self-adhering polymer bitumen tape (min. 4″ wide) over decking joints.
- Most allow a self-adhering waterproof membrane to be applied directly to the deck.
- Dade/Broward requires the underlayment to be a #30 felt nailed in a tightly prescribed pattern.
- The surface layer can be a self-adhesive membrane or a hot-mop fastened #90 bitumen cap sheet.
- There are prescribed methods to install flashing to valleys, ridges, dormers, chimneys and walls.
- Prescribed procedures exist for fastening metal drip edges, vents, skylights & other protrusions.
HURRICANE PROOF ROOFS
Hurricane Proof offers the latest proven roofing technology in all categories of roof coverings as described below.
There are two basic methods of manufacturing shingles. Composition shingles are made of organic felt manufactured from wood and paper fibers. Fiberglass-base shingles are made of manmade fiberglass mat. Both kinds are soaked in asphalt and have mineral granules embedded in them. The fiberglass-base shingles are more fire and wind resistant and have longer life.
Three-tab shingles are the roofing industry’s standard. The lower (exposed) half of the shingle is notched into three integrated pieces, or tabs. Architectural (dimensional) shingles are created by bonding two asphalt shingles together, giving them a distinct three-dimensional appearance.
All shingles have a heat-activated adhesive strip that bonds them into a single, watertight unit. Most shingles come with a 10-year to 30-year limited product warranty and 10-year coverage against algae growth. Wind resistance limited warranties are generally for winds of between 90 and 120 mph. A Class-A Fire Rating is the highest available for residential applications. As important as selecting shingles is to have them properly installed as summarized below
- proper nails (min. 3/8″ head ring shank made of galvanized or stainless steel, copper, or aluminum)
- proper nailing (minimum 6 nails each straight & flush with shingle and 1″ deck penetration)
- tab adhesion (min. three 1″ dabs of asphalt adhesive per end of each tab)
- edge adhesion (additional dabs on starter row & ridge shingles, 4″ wide layer on roof edges)
- flashing must be coated with primer and/or flashing cement to ensure adhesion to shingles
Concrete and clay tiles have existed for centuries. Recent developments have further improved this attractive roof option. Concrete tiles are Class A fire rated, resistant to hail damage and can sustain winds in excess of 125 miles per hour resulting in warranties up to 50 years. Concrete tile roofs are also superior in energy conservation. Tile roofing’s mass, reflectivity nd ventilation contribute to at least a 50 percent reduction of heat transfer when compared with traditional asphalt shingles. Finally, concrete tiles are built from relatively abundant materials in comparison with asphalt shingles (petroleum based) and metal roofs.
There are many style and color options available with concrete tile. Modern concrete tile designs can simulate the appearance of traditional clay tiles, wood shake, slate and stone. Concrete tile surfaces can be textured or smooth, tile edges can be uniform or ragged, and architects may select tiles of all one color, blended colors or combinations of two or more shades placed in a uniform or random pattern. Pigments can be blended to allow for virtually any desired color, including bright whites, pastels and deep rich shades. Shapes are typically classified into three categories; flat, low profile (i.e. Spanish or interlocking S tile) and high profile (i.e. Mediterranean or barrel tile).
While the tiles themselves are wind resistant, their method of attachment has been inadequate as proven in several recent hurricanes. Advanced application products and procedures have vastly improved the wind resistance capability of tiles. The tiles themselves are best installed with foam-adhesive, which provides a strong and uniform bond to a large section of the tile and underlayment. All ridges now require a securely fastened (adhesive-set and screwed) wood ridge board or metal ridge “hat” to which the ridge tiles are fastened (also by adhesive-set and screws or nails). In addition to the foam, it’s recommended that a clip be installed on each tile in the first row of tiles.
Metal roofs are considered to be the most resistant roofing material to hail, wind, fire, and freezing/thawing. They are most durable and longest lasting roofing option. Therefore, metal roofs offer the highest warrantee (40 years and up) and are the most expensive. Depending on design and color, metal roofs can be very energy efficient due to their reflective qualities. They are virtually maintenance free and are recyclable after their long life.
Metal roofing products are available in a wide range of metals including steel, aluminum, copper, zinc, stainless steel, and titanium. The predominant metal roofing substrate is metallic-coated steel sheet. The metallic coatings include aluminum, galvanized (zinc), Galavalume® (55% aluminum-zinc alloy), Galfan® (5% aluminum-zinc alloy and terna (lead-tin alloy). Some metal panels are left in their natural color, while most receive a painted or aggregate (stone) finish. A new “cool pigment” technology provides metal roofs with an oven-cured, pre-painted organic coating that offers higher total solar reflectance even with darker colors.
Metal roofs are now available in wide variety of styles. Historically, metal roofs have been offered in an array of vertical panels with varying degrees of strength and appearance. These include:
- Classic rib panels, corrugated panels (wave shape), and 5-V crimp panel
- Standing seam (raised seam adds strength, includes double locking seams and hidden fasteners)
- Strap seam with striations (includes strap seam with striations and nailer strips)
Recently, horizontal metal panels are available that simulate the look of other common roofing materials including shingles, shake, slate, and tile.
There is no standard fastening system for metal roofs due to the wide variety options. Practically all metal panels feature overlapping seams for strength and water protection. Double locking seams provide the highest level of both. The keys to getting a wind resistant metal roof installation are to ensure that the lowest panel fasteners are installed close to the roof eave and that the manufacturer’s recommended spacing for fasteners is followed carefully. Many of the past failures in metal roofs have been in the panels covering hips and ridges. Newer metal ridge caps have screws along the bottom edge to improve strength.