PATH - A Public Private Partnership for Advancing Housing Technology

Build to Improve Storm-Resistance

Hurricane season arrives and homeowners brace for the worst. Will your homes escape with only minor damage? You can increase those odds with these guidelines, developed from years of PATH studies on the effects of hurricanes on homes.

[IMAGE: Florida home built with PATH technology -- before the hurricane.] [IMAGE: After the hurricane -- the home only lost a gutter and surrounding landscaping.] For example, PATH technology helped some homes in Port Charlotte, Florida, stand up to Hurricane Charley in 2004. The home pictured left was built with fiber-cement SIPs and suffered damage to one gutter, while other homes in the neighborhood were leveled.

Interested in strengthening a home against future hurricane damage? PATH recommends ways to repair and protect homes.

BUILD TO IMPROVE HURRICANE RESISTANCE

Building a new home? Consumers should consider these steps.

Industry professionals should consider the following guidance.

Building Materials: Construction materials should be resistant to damage from bulk water intrusion including floods and major rain events. Preferred building material attributes for flood-prone regions include:

• Absorbs little or no moisture
• Dries without long-term damage
• Few voids within assemblies
• Affordable and market acceptable
• Integrated insulation that resists moisture
• Configurable into multiple housing types

Building Design: Homes located in flood-prone areas should be designed with all living spaces located above the designated flood-plain elevation

Planning: Where practical, higher density planning should be employed to concentrate housing is less flood-prone areas.

WIND VS. WATER

PATH has evaluated homes hit by hurricanes, and has uncovered some surprising results:

• Wind damage accounts for only a fraction of the destruction
• The greatest destruction was caused by water infiltration, not catastrophic structure failure

Strategies to Limit Wind-Driven Water Intrusion

• Follow PATH Tech Set #5: Storm Resistant Roofing
• Use baffled ridge vents and off-ridge vents instead of unbaffled vents. Unbaffled vents tend to allow wind-driven moisture to enter attic spaces or the cavities of cathedral ceilings, causing moisture damage and mold growth.
• Install front doors so they swing out instead of into the house. Out-swinging doors are more resistant to wind loads, and they do a better job preventing water infiltration.
• Use capillary breaks where concrete walls meet the slab. Capillary breaks suspends the flow of rainwater hitting the walls where they meet the concrete floor slab: preventing water infiltration through small cracks at the slab/wall juncture.
• Apply elastomeric sealant at concrete walls. These finish coatings prevent water absorption during heavy storms. Pay special attention to seal at the wall's snap-tie locations.
• Extend fascia board to terminate below the underside of the soffit. This helps keep water out of the eaves.
• Install a natural-gas powered generator in the home. Homes subject to water infiltration can more easily prevent mold growth and rot if they dry out quickly. Generators allow fans and dryers to be used quickly after a hurricane, when electrical power is usually gone, often for extended periods.

These recommendations were published in the July 2005 issus of Professional Builder, Building for Survival in Hurricane Country.

Strategies to Improve Wind Resistance

• Follow PATH Tech Set #5: Storm Resistant Roofing
• Cast-in-place concrete construction. Concrete construction withstands winds better than stick-built structures, and cast-in-place concrete walls are stronger than concrete masonry unit block.
• Direct load path. Aligning the roof trusses with interior load bearing wall framing improves the up-lift resistance.
• Hurricane straps. Line up bracing and tie-downs at critical load points to maintain the integrity of the load path. Use light-gauge steel straps to anchor the first story to the foundation. (During Hurricane Andrew, hurricane ties had a 92 percent success rate.)
• Additional reinforcing. Added steel reinforcing around windows and sliding glass doors helps keep these units in place during high winds.
• Proper nailing schedule. Size, type and placement are all factors. Nail edge distance tolerance is quite tight (acceptable nail edge distance should be 1/4 to 3/4 inch) and the nail overdrive can reduce uplift strength of the connection significantly. Thicker sheathing can offset sensitivity to overdriving.
• Ring-shank nails. To secure sheathing panels in high wind-prone areas with basic wind speeds of 110 mph or greater, ring-shank nails are recommended for their higher withdrawal capacity. Costs are comparable, and with a slightly smaller diameter, they offer the added benefits of less frequent reloading of pneumatic nail guns and more forgiving edge distance tolerances.
• Secondary roof covering. Peel-and-stick roof underlayment mitigates water intrusion if roof shingles are lost. These rubber or asphalt sheets cost $700 to $1000 more than standard roofing felt for a 2,400 square foot house.
• Window shutters. Permanent or removable shutters reduce forces on the structure and minimize water- and wind-related damages to the interior by protecting windows. Storm-resistant shutters for a standard single-story home with 312 square feet of windows cost about $700.

These recommendations are based on Building for Survival in Hurricane Country, the PATH report Durability by Design, and lessons from a PATH site demonstration in Melbourne, Florida. In the Florida demonstration, a PATH team examined how to exploit the strength of poured concrete walls to enable homes to weather a major storm.

MORE RECOMMENDATIONS

Learn what PATH technologies can help you speed up the rebuilding process.

Cleaning up water damage? Read PATH recommendations for flood recovery.

PATH recommends ways to repair and protect an existing home.

Remodeling? Use the Rehab Advisor to learn how to save money on utility bills.

Content updated on 5/21/2007

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