Preventing Lift Off of the House Roof or its Components

Floods December 09, 2013|Print


Keeping the roof on a house is important for preventing water, wind, and hurricane damage. Damage from high winds and water often occurs because part of or the entire roof lifts off. To see how a roof may be damaged or removed by high winds, visit FLASH and click on "roof."

Contact your local code and zoning officials before using any of the methods described here. Seek professional licensed or experienced contractors or engineers for assessments and to do the work, especially if you are not qualified to perform the work.


Keeping Roof Members Attached

  • Use corrosion-resistant metal connectors. Install the correct connector size and type according to manufacturer and engineer recommendations. In high wind areas, toenailing is not recommended as a method to prevent roof uplift.
  • Connect each truss part or joint with metal connectors. Fasten the roof trusses or rafters directly to the load bearing wall studs with hurricane straps and appropriate connectors. Alternatively, use hurricane clips, ties, hangers, or straps to fasten each roof rafter to the top of the exterior wall top plate and then attach the top plate to the wall studs with a connector. Continue strapping and connectors until the roof, wall system, and foundation are anchored together. Eave soffits or siding may need to be temporarily removed for access to the top plate and trusses.
Hurricane straps or appropriate connectors fasten trusses or rafters to load bearing wall. University of Nebraska-Lincoln, Shirley Niemeyer.


Reinforcing Connections of the Roof System to Load Bearing Walls

 

Reinforce connections. Photo: FEMA, Jon Ayscue.

 

Reinforce roof and truss connections. University of Nebraska-Lincoln, Shirley Niemeyer.

 

Connect truss members and rafters to the wall. Source: University of Nebraska-Lincoln, Shirley Niemeyer.

 

• Roof-related connections include truss members, truss-to-truss, rafter-to-truss, roof-to-wall and stud-to-top plate connectors.

• Wall and foundation connections include stud-to-top plate, stud-to-stud, header, joint-to-beam, wall-to-foundation, continuous rod, and pile connectors.

• Gable walls must be able to withstand considerable pressure in high-wind storms. They are weak points in many homes. Reinforce gable end walls by bracing the gable wall to the attic floor. One method is to place two 2 x 4 inch boards in an X shape inward or perpendicular to the center of the gable. Attach one board end at the center peak of the gable and one end at the bottom of the gable center. The remaining two ends are then anchored in an X fashion with screws to about the 4th truss and the truss between the gable end and the 4th truss. (Source: Institute of Business & Home Safety (IBHS). Against the Wind.)

Reinforce structure with bracing. Illustration courtesy of Purdue University, Kimberly Batta.

 

• If truss bracing is not evident in the attic, run 2 x 4 inch boards the length of the roof attaching them to each truss. Overlap the ends of the boards across two trusses and attach with screws or 16d common nails. The boards should be spaced about 18 inches down from the ridge of the attic, at the center, and at the base near the eave of the roof. (Source: IBHS. Against the Wind.)


Keeping the Sheathing on.(Check Local Code Requirements.)

• Sheathing loss is common in high winds and hurricanes. Loss of the entire roof can result from the loss of just one piece of sheathing. The result can be major interior water damage.

• If possible, use at least 5/8 inch plywood for roof decking.

• If you are replacing shingles, fasten or refasten the roof sheathing with #8 screws (check codes) every 4 inches at the edges and eaves of the roof where winds can be especially damaging. Place other screws about 6 inches apart throughout the decking. Although 2 ½ inch (8d) or longer ring or screw shank nails can be used, screws are recommended because of their greater strength and holding ability. Stapling sheathing in place is not recommended for high wind areas. All screws or nails must connect with the roof framing (rafters, trusses). Tape the decking seams with self-adhering asphalt rubber tape for added water resistance.

 

Stagger plywood sheathing or decking seams. University of Nebraska-Lincoln, Lisa Comes.


• Work from the attic side to reinforce the sheathing if you are not replacing the shingles. Secure the rafters or trusses to the roof sheathing or deck. Use a caulk gun and wood adhesive to caulk both sides of the rafters or roof trusses.

Reinforce decking to rafters or roof trusses from inside. University of Nebraska-Lincoln, Lisa Comes.


• Consult local codes and recommendations for roofing in your area. If you use roofing felt paper as an underlayment, install it as a double layer with staggered overlaps using tincap metal discs and roofing nails or capped-head nail fasteners. Use hot-dipped galvanized or stainless fasteners, especially if they may be exposed to saltwater. In some areas, a self-adhering modified bitumen layer is installed over a single layer of the felt. Peel and stick membranes secured directly to the decking also are used, although they may require a decking preparation. Follow the manufacturer’s recommendations.

Peel and stick membrane. University of Nebraska Lincoln, Shirley Niemeyer.

 

• Use shingles rated for the maximum wind speeds in your area or shingles that are rated for hurricane-force winds. Although more costly, the high-wind shingles may come with a 30- to 50-year limited product warranty. Consult local codes for product and installation regulations and review the manufacturer’s recommendations. Look for shingles that have been tested in accordance with wind-resistance rating system UL 2390. Although metal and tile roofs are durable, they must be correctly installed. Tiles should be installed with screws.

• Instead of staples, use about 6 nails per tab shingle, and screws for tile roofs. Use nails that extend through the roof sheathing.

• At the roof eaves, gable end edges, and at the hip and ridges, use quick-setting asphalt roof cement under each asphalt shingle tab to add more strength and water and wind resistance.

• Use both ridgerow baffled vents and soffit vents to reduce upward pressure on the sheathing in vented attics.

Ridgerow baffled vents to reduce wind driven water. Photo: University of Nebraska-Lincoln, Shirley Niemeyer.


Damage from high winds and water often occurs because a part of or the entire roof lifts off or the roof surface fails. Damage may be reduced by using reinforcement strategies and by strengthening the attachments and surfaces of the structure’s components. Obtain additional information before making decisions about reinforcing the roof structure and its components.


Resources

American Red Cross Organization. http://www.redcross.org.

Federal Emergency Management Agency. Home Builder's Guide to Coastal Construction. Asphalt Shingle Roofing for High-Wind Regions. Technical Fact Sheet #20, Aug. 2005.

Federal Emergency Management Agency. Home Builder’s Guide to Coastal Construction. Roof Sheathing Installation. Technical Fact Sheet #18.

Federal Emergency Management Agency. Home Builder's Guide to Coastal Construction. Roof Underlayment for Asphalt Shingle Roofs. Technical Fact Sheet #19.

Federal Emergency Management Agency. Home Builder's Guide to Coastal Construction. Storm-Resistant Roofing.

Federal Emergency Management Agency. Home Builder’s Guide to Coastal Construction. Use of Connectors and Brackets. Technical Fact Sheet #17.

Federal Emergency Management Agency. Homeowner's Guide to Retrofitting: Six Ways to Protect Your House from Flooding, chapters 3 and 7.

Parker, D. (2006). Post-Hurricane Opportunities. Hurricane Season. Home Energy, pp. 38-40.

U.S. Department of Housing and Urban Development. Durability by Design: A Guide for Residential Builders and Designers.


For more information on recommendations for your zip code area, go to the Institute of Business and Home Safety website and click on "Fortified for Safer Living."

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