Roofing: Shingle Roof Installation

In areas prone to hail and high winds, including severe thunderstorms, hurricanes and tornadoes, all shingle roof coverings should:

  • Be rated for the ASCE 7 design wind speed for the site location of the building.

  • Meet appropriate impact resistant standards (UL2218).

  • Be installed in accordance with the manufacturer’s recommendations for high-wind regions.

  • In hail-prone areas, where the wind speed does not exceed 110 mph, choose an asphalt shingle that meets both ASTM D 7158 Class G or H (or ASTM D3161 Class F) and UL 2218 Class 4 for optimal protection from high wind and hail. See Table 1 for additional information.

Shingle Wind Testing Standards:

ASTM is a standards organization that publishes technical standards for a wide range of materials and products, including test standards for the wind resistance of asphalt shingles. The ASTM shingle wind testing standards and classification system, not the advertised warranty period and warranty wind speed, will determine which class of high-wind rated shingles meet the technical requirements for a specific wind speed. Make sure the shingles chosen meet these test standards and classification and that the installation is in accordance with the manufacturer’s recommendation for high-wind installations. Asphalt shingles-including hip and ridge materials- must meet the shingle testing standard for the appropriate site design wind speed as shown in Table 1.

Shingle Impact Resistant Standards:

UL 2218 is a test that is administered by Underwriters Laboratories and involves dropping steel balls of varying sizes from heights designed to simulate the energy of falling hailstones. Class 4 indicates that the product was still functional after being struck twice in the same spot by 2” steel balls. Note that this standard is appropriate for flexible roofing products like asphalt shingles, and metal panels or shingles. Asphalt shingles should meet the impact resistant classification shown in Table 1.

Refer to the UL Online Certifications Directory that maintains a list of UL Certified Clients for Roof Covering Materials, Impact Resistant, UL 2218. Click on a manufacturer’s file (far right column) to find out the class rating for their product.

Steps to a Stronger Roof

1. Remove the existing roof cover down to the deck

  • The building code does not permit the installation of a new layer of shingles directly over the top of existing shingles in areas with moderate to severe hail exposure.

  • Exposing the sheathing allows for improvement of the fastening of the sheathing to the roof framing, which will help the roof perform better in high winds.

  • It also provides a smooth solid foundation for installing a wind and impact resistant roof cover.

2. Replace any damaged decking or roof framing members

Replace any sections of the roof deck or supporting roof framing members that are damaged or deteriorated.

3. Re-nail roof deck

Check the nailing of the roof deck to the rafters or trusses that support the deck.

For wood plank decks:

The existing nailing has generally proven to be adequate if at least two nails were installed every time one of the planks crossed a rafter or truss and the planking is not too wide.

For wood panel sheathing (plywood or Oriented Strand Board, OSB):

    • The commonly used nail sizes and nail spacing, particularly along trusses and rafters in the middle of the panels, have not always been adequate in providing the needed resistance to uplift in high wind events.
    • Engineering testing and experience have shown that staples are not very effective in holding down roof sheathing, regardless of how close together they may be. The cost of adding nails when the roof deck is already exposed is small in relation to the benefit.

Guidance by lumber type:

Sawn Lumber or Wood Board Roof Decking:

    • Add fasteners as required to ensure that roof decking consisting of sawn lumber or wood boards up to 1-in. thick are secured with at least two nails, having a minimum diameter of 0.131 in. and a minimum length of 2-1/2 in., (three nails if the board is wider than 8”) to each roof framing member it crosses.
    • Framing members must be spaced no more than 24 in. apart.
    • Clipped-head, D-head or round-head nails are fine provided they have the required minimum diameter and length.
    • For wood boards greater than 1-inch thick and up to 2 inches thick, add fasteners as required to ensure that the decking is secured with at least two nails, having a minimum diameter of 0.131 in. and sufficient length to penetrate a minimum of 1-5/8 in. into the roof framing, (three nails if the board is wider than 8 in.) to each framing member it crosses.

Wood Board/Lumber Roof Decking:

Maximum spacing of framing members:

    • Up to 8 in. (2)- 0.131 in. minimum diameter with 1-5/8 in. penetration into roof framing members 24 in.
    • Larger than 8 in. (3)- 0.131 in. minimum diameter with 1-5/8 in. penetration into roof framing members 24 in.

Structural Wood Panel (Plywood or Oriented Strand Board-OSB) Roof Sheathing:

The number and spacing of additional fasteners needed to adequately strengthen the connection of structural wood panel roof sheathing depends on the size, type and spacing of the existing fasteners.

The specific required minimum dimensions and characteristics for the additional ring-shank nails to be used to strengthen the roof deck attachment are:

    • full round head diameter (no clipped head nails allowed)
    • 2-3/8 in. minimum nail length
    • 0.113 in. in diameter

Additional guidance:

  • Roof sheathing panels should be minimum of 7/16 in. thick.
  • Roof framing members should be spaced no more than 24 in. apart and have a minimum 2 in. nominal thickness
  • Existing 8d nails should be a minimum of 0.131 in. in diameter and 2-1/2 in. long.
  • For the additional fasteners, IBHS recommends using 8d ring shank nails with the following minimum dimrnsions (0.113” x 2-3/8” with full round head).
  • Roof pitch should be 2/12 or greater. 

4. Seal the Roof Deck: 

Historically, the roofing industry has referred to the felt paper used as underlayment as a sealed roof deck because it provides a drainage plane for any water that gets behind the roof cover. In the context of this guide, typical felt underlayments do not qualify as a sealed roof deck. A sealed roof deck stays in place and prevents water from pouring into the attic if the primary roof cover is lost or damaged. A sealed roof deck is an added level of protection for your home and is relatively inexpensive to install when you’re re-roofing.

Important note for cold weather areas:  As a minimum precaution in areas, where there has been a history of ice forming along the eaves and causing a backup of water, an ice barrier that consists of a least two layers of underlayment cemented together or of a self-adhering polymer modified bitumen sheet, should be used in lieu of normal underlayment and extend from the lowest edges of all roof surfaces to a point at least 24 in. inside the exterior wall line of the building.

Sealed Roof Deck Options

Install a “peel and stick” membrane over the entire roof deck:

  • Cover the entire roof deck with a full layer of self-adhering polymer modified bitumen membrane (“peel and stick”) meeting ASTM D1970 requirements. In some instances, the ability of the self-adhered membranes to adhere to Oriented Strand Board (OSB) sheathing may be compromised by the level of surface texture, the amount of wax added to the OSB panel, and the job site conditions.
  • In applications where membrane adhesion to OSB is marginal, apply a primer to the OSB panels to ensure the proper attachment of the self-adhering membrane to the sheathing. It should also be noted that most manufacturers warn that attic ventilation must be good if these products are used because moisture in the attic cannot evaporate through these types of membranes.
  • Roofers are finding that shingles are bonding to many of these membranes and this could lead to damage of the sheathing when it comes time to replace the shingles. Consequently, the membrane should be covered with a bond break such as a 15# ASTM D226, Type I underlayment.

This underlayment for the shingles only needs to be fastened sufficiently to keep it on the roof surface and provide safety to the roofers until the shingles are applied.

Note: Some local building departments (e.g. Miami-Dade and Broward counties in Florida) prohibit the use of a self-adhered membrane applied directly to the roof sheathing. Check with the local building department for any restrictions in your area.

Install 4-in. to 6-in wide “peel and stick” tape installed over all the wood roof panel seams, covered by a 30# felt underlayment over the entire roof:

  • Apply a self adhering polymer modified bitumen flashing (“peel and stick”) tape 4”-6” wide directly to the roof deck to seal the horizontal and vertical joints in the roof deck. In some instances, the ability of the self-adhered membranes to adhere to Oriented Strand Board (OSB) sheathing may be compromised by the level of surface texture, the amount of wax added to the OSB panel, and the job site conditions.
  • In applications where membrane adhesion to OSB is marginal, apply a primer to the OSB panels to ensure the proper attachment of the self-adhering tape to the sheathing. Do not nail or staple the tape to the roof sheathing.
  • Refer to the manufacturer’s recommendations for installation.
  • Next apply a code compliant 30# ASTM D226, Type II underlayment over the self-adhering tape. This underlayment must be attached using annular ring or deformed shank roofing fasteners with minimum 1” diameter caps at 6” on center spacing along all laps and at 12” on center in the field or a more stringent fastener schedule if required by the manufacturer for high wind installations.
  • The minimum horizontal overlap between rolls is 2-inches and the minimum overlap at the ends of rolls (vertical) is 6-inches.
  • Nails with plastic or metal caps may be used in areas where the design wind speed is less than 140 mph. Metal caps should be used in areas where the design wind speed is greater than or equal to 140 mph.
  • A self-adhering polymer modified bitumen membrane complying with ASTM D1970 may be installed over this underlayment in order to comply with FEMA technical fact sheet No. 19.
  • The “peel and stick” option is recommended for areas with design wind speeds greater than 120 mph.

Install high tear strength synthetic underlayment with all vertical and horizontal seams taped:

  • Apply a reinforced synthetic roof underlayment which has an ICC approval as an alternate to ASTM D226 Type II felt paper. The synthetic underlayment must have minimum tear strength of 20 lbs. per ASTM D1970 or ASTM D4533.
  • This underlayment must be attached using annular ring or deformed shank roofing fasteners with minimum 1 inch diameter caps at 6 inches on center spacing along all laps and at 12” on center in the field or a more stringent fastener schedule if required by the manufacturer for high wind installations. Metal caps are required for areas where the design wind speed is greater than or equal to 140 mph.
  • The minimum horizontal overlap between rolls is 2 in. and the minimum overlap at the ends of rolls (vertical) is 6-in.
  • All seams should be sealed with a compatible adhesive or a compatible 4-in. wide tape except for steep slope roofs with a 12/12 roof pitch (45 degrees) or greater.
  • Horizontal seams on steep slope roofs with a 12/12 pitch (45 degrees) or greater do not have to be sealed with adhesive or tape provided the overlap for horizontal seams is at least 18 inches.
  • A self-adhering polymer modified bitumen membrane complying with ASTM D1970 may be installed over this underlayment in order to comply with FEMA technical fact sheet No. 19.
  • The “peel and stick”option is recommended for areas with design wind speeds greater than 120 mph. Provide these installation instructions for sealing the roof deck to your contractor to ensure proper product selection and installation.

5. Install high-wind, impact-rated shingles

Follow the manufacturer’s instructions for a high-wind installation.

This article is part of a larger series on new and existing roofing.