Tornadoes: Roof - Choosing the Right Covering

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Many tornado prone areas are also prone to hail. To protect roof coverings from both wind and hail damage, look for wind and impact rated roof coverings. For shingles, wind ratings are based on standards published by ASTM International (formerly known as the American Society for Testing and Materials) and resistance to impact is based on an Underwriters Laboratory test, UL 2218.  For the highest level of wind rated shingle, look for shingles that are rated to ASTM D3161 Class F or ASTM D7158 Class H. For the highest level of impact protection, look for shingles that meet UL 2218 Class 4.

Asphalt Shingles

Pros:

  • Relatively low cost, lightweight, and easy to install. 
  • Good fire resistance (usually Class A).
  • UL 2218 Class 3 and 4 impact resistance is available, should be used in hail regions. 
  • Available with wind warranties up to 130 mph, if installed in accordance with manufacturer's high wind requirements.

Cons:

  • Aging and weathering may decrease effectiveness in high winds and impact resistance

 

Recommended installation

  • The first course of shingles should be sealed to the starter strip with dabs or bands of roof cement. Details are provided in FEMA 499, Technical Fact Sheet No. 7.3.

 

Metal

Pros:

  • Attractive and relatively lightweight
  • Last up to 40 years
  • May have a Class A or B fire rating

Cons:

  • Cosmetic damage from hail may cause permanent dimples

Recommended Installation:

  • Use clips or cleats instead of exposed fasteners because they aren’t exposed to weather and allows the metal to expand and contract reducing the opportunity for buckling
  • If exposed fasteners are used, they should be corrosion resistant and penetrate the sheathing

 

Slate

Pros:

  • Can last three times longer than shingles

Cons:

  • Expensive and very heavy
  • Some roof structures are unable to support slate

Recommend Installation:

  • Should be attached with flat head copper-wire slating nails
  • In high wind areas, apply a dab of roof cement or polyurethane sealant under the exposed part and the slate
  • Install using four nails per slate in high wind areas
  • High quality, durable underlayment recommended

 

Tile

Pros:

  • Popular in some areas
  • Available in concrete or clay
  • Concrete tiles are more durable and can last more than 30 years

Cons:

  • Performance in hail storms varies by type.
  • Clay tiles are brittle and can be easily chipped or broken
  • Tiles are heavy and some structures are unable to support the weight
  • Can take longer to install making labor costs more expensive

Recommend Installation:

  • Use wind clips or storm anchors in high wind or seismic areas
  • Two screws per tile give the highest wind uplift resistance and will help the tile resist shifting
  • Installation is critical in high wind areas, especially hip and ridge tiles
  • A high quality, water resistant underlayment is required

 

Wood Shingles and Shakes

Pros:

  • Made from cedar, southern pine or other woods
  • Attractive appearance
  • Perform moderately well against hail

Cons:

  • Some local codes limit their use
  • May not be rated for fire unless they’re treated with a fire retardant 

 

Tips

Keep these points in mind when you have your roof covering repaired or replaced:

  • If you are having an old roof replaced, your contractor should remove the existing shingles and underlayment rather than install new shingles over them. This approach allows the contractor to inspect the sheathing and make any repairs that may be necessary.
  • The first course of shingles should be sealed to the starter strip with dabs or bands of roof cement. Details are provided in FEMA 499, Technical Fact Sheet No. 20.
  • If your building is within 3,000 feet of saltwater, the nails or screws should be stainless steel.
  • Check local code requirements for roof repair or replacement criteria. Your local building official should be able to provide additional recommendations. 

 

Benefits of Using This Mitigation Strategy

Helps to prevent damage to a structure and its contents

Helps to prevent injuries to occupants 

Estimated Costs

The cost of re-roofing varies based on the roof pitch, damage to underlayment, quantity of roofs on the home, and location of the home. Typically, a low pitch, single story home with asphalt shingles will cost around $40 - $80 per square (100 sq. ft.). This estimate will increase to roughly $75-$100 to remove old shingles and install new shingles. Damaged underlayment will cost more to repair, roughly $50 per sheet. Expect additional charges for flashing piping and chimneys.  Any variables including, steep pitch, roofing material, second story roof, will also increase costs. .1

 

1."What Is the Average Cost per Square Foot to Install Roof?" WikiAnswers. Answers. Web. 31 May 2012. http://wiki.answers.com/Q/What_is_the_average_cost_per_square_foot_to_install_roof.

 

 

 

 





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