Roofing: Tile Roof Installation

In all areas prone to high winds, such as hurricanes and tornadoes, and hailstorms, choose a tile roof covering that meets installation guidelines for these conditions and impact resistant test standards:

  • It is important to choose a roof covering and to have it properly installed for both the requirements for the site design wind speed and impact test standard FM 4473 Class 4 for optimal protection. Before choosing a product, find out the ASCE 7 design wind speed for the site location.

  • Mortar set tile or mortar set hip and ridge tile option is not recommended in high-wind areas. A recent study by tile industry experts suggested more than 30 potential problems with a mortar set installation in high-wind conditions.

Guidelines for wind and impact resistance

Clay and Concrete Tile Wind Resistance Requirement:

For tile roofs, the accepted US standard for proper installation in high wind areas is the Florida Roofing, Sheet Metal and Air Conditioning Contractors Association (FRSA)/ Tile Roofing Institute installation guidelines, Concrete and Clay Roof Tile Installation Manual Fourth Edition, FRSA/TRI 07320/08-05.

These guidelines are available for purchase at a reasonable price from the Tile Roofing Institute or the Florida Roofing, Sheet Metal and Air Conditioning Contractor’s Association.

Tile Impact Resistant Standards:

  • FM 4473 is administered by Factory Mutual Research and is a test that is similar to the UL 2218 impact resistant test for shingles, but instead of using steel balls, frozen ice balls are used. The FM 4473 test standard is used on rigid roof covering materials (like concrete, clay, or slate) and involves firing the ice balls from a sling or air cannon at the roof-covering product.

  • A Class 3 rating indicates that the product was still functional after being struck twice in the same spot by a 1-3/4 in. ice ball

  • A Class 4 rating requires impact with 2 in. ice balls.

  • IBHS recommends using a Class 4 rating when possible; however, a Class 4 rating is available for only a limited number of products. A Class 3 rating expands the number of available products. 

Steps to a Stronger Roof

1. Remove the existing roof cover down to the deck

  • 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.

2. 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-inch thick are secured with at least two nails, having a minimum diameter of 0.131 inch and a minimum length of 2-1/2 inches, (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 inches 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 inches and sufficient length to penetrate a minimum of 1-5/8 inch into the roof framing, (three nails if the board is wider than 8 inches) to each framing member it crosses.

Wood Board/Lumber Roof Decking:

Maximum spacing of framing members: – Up to 8” (2)- 0.131” minimum diameter with 1-5/8” penetration into roof framing members 24 inches – Larger than 8” (3)- 0.131” minimum diameter with 1-5/8” penetration into roof framing members 24 inches

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” minimum nail length

  • 0.113” in diameter

Additional guidance:

  • Roof sheathing panels should be minimum of 7/16” thick.

  • Roof framing members should be spaced no more than 24” apart and have a minimum 2” nominal thickness.

  • Existing 8d nails should be a minimum of 0.131” in diameter and 2-1/2” 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.

3. 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 cap sheet (“peel and stick”) meeting ASTM D1970 requirements.

  1. 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.

  2. 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.

  3. In addition, 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-in. to 6-in. wide directly to the roof deck to seal the horizontal and vertical joints in the roof deck.

  1. 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.

  2. Do not nail or staple the tape to the roof sheathing. Refer to the manufacturer’s recommendations for installation.

  3. 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-inch diameter caps at 6 inches on center spacing along all laps and at 12 in. on center in the field or a more stringent fastener schedule if required by the manufacturer for high wind installations.

  4. The minimum horizontal overlap between rolls is 2 inches and the minimum overlap at the ends of rolls (vertical) is 6 in.

  5. Nails with plastic or metal caps are allowed in areas where the design wind speed is less than 140 mph. Metal caps are required for areas where the design wind speed is greater than or equal to 140 mph.

  6. Finally, apply a self adhering polymer modified bitumen cap sheet complying with ASTM D1970 over this underlayment.

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-in. to 6-in. wide directly to the roof deck to seal the horizontal and vertical joints in the roof deck.

  1. 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.

  2. 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 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.

  3. 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 are allowed in areas where the design wind speed is less than 140 mph. Metal caps are required for areas where the design wind speed is greater than or equal to 140 mph.

  4. Finally, hot mop the underlayment using hot asphalt and apply a 90# mineral surface cap sheet.

4. Install high-wind, impact-rated roof tiles

Follow the manufacturer’s instructions and the FRSA/ Tile Roofing Institute installation guidelines, Concrete and Clay Roof Tile Installation Manual Fourth Edition, FRSA/TRI 07320/08-05.