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  1. Kelsey McMenamy

    Section 706.7.2 of the FBC Existing Building Code notes that for HVHZ reroof projects, a secondary water barrier is required by use of 4-6" SA stripping over the plywood deck joints and a 30# felt is required atop that. It also notes that "No additional underlayment shall be required over the top of this [30#] sheet). Note this does not apply to roof slopes < 2:12 or clay/concrete tile roofs. Could you please help explain what this means and what will be required for steep-slope reroofs (non-tile)? Is the 30# felt considered a "water barrier"? And therefore, once the joints are stripped in and the 30# is applied, another water barrier (continuous SA mod bit sheet) would not also be required? Please also confirm that the stripping is not required for the non-HVHZ zones, and that for reroofs and new construction, just a single layer of SA mod bit can be applied direct to the deck? Thank you!

    1. Lyle Jacobs

      Is the 30# felt considered a "water barrier"?

      Based on the FBC, Yes, in the HVHZ (Broward and Miami-Dade Counties).

      In the Non-HVHZ compliance with one of the methods provided in the FBC Residential Code, sections R905.1.1.1, R905.1.1.2 or R905.1.1.3, as applicable, is required.

      And therefore, once the joints are stripped in and the 30# is applied, another water barrier (continuous SA mod bit sheet) would not also be required?

      That is correct for the HVHZ (stripping the joints and then installing a 30# is one of the options allowed in the HVHZ as a complete method).

      In the Non-HVHZ compliance with one of the methods provided in the FBC Residential Code, sections R905.1.1.1, R905.1.1.2 or R905.1.1.3, as applicable, is required.

      Please also confirm that the stripping is not required for the non-HVHZ zones,

      In the Non-HVHZ compliance with one of the methods provided in the FBC Residential Code, sections R905.1.1.1, R905.1.1.2 or R905.1.1.3, as applicable, is required. One of the options provided is for utilizing the 4” strip of self-adhering polymer-modified bitumen membrane complying with ASTM D1970. Then an approved underlayment in accordance with Table R905.1.1.1 for the applicable roof covering shall be applied over the entire roof over the 4-inch-wide (102 mm) membrane strips. But other approved options may be utilized.


      And that for reroofs and new construction, just a single layer of SA mod bit can be applied direct to the deck?

      Yes, only in NON-HVHZ areas of the State. That is one of the options provided in the FBC, Residential, sections R905.1.1.1, R905.1.1.2 or R905.1.1.3.

      This method is not allowed in the HVHZ.

      Could you please help explain what this means and what will be required for steep-slope reroofs (non-tile)?

      The Exception contained in Section 706.7.2 is applicable for the entire section and therefore applicable in the HVHZ and Non-HVHZ areas of the State. Consequently, the requirements of 706.7.2 do not apply to:

      Roof slopes < 2:12 having a continuous roof system shall be deemed to comply with Section 706.7.2 requirements for a secondary water barrier.

      Clay and concrete tile roof systems installed as required by the Florida Building Code are deemed to comply with the requirements of Section 706.7.2 for Secondary Water Barriers.

      The way the code is written, a continuous roof system with a slope > 2:12 and is not a concrete or clay roof tile system would require compliance with Section 706.7.2.

      Commentary:

      Florida Statute 553.844 establishes the requirements for windstorm loss mitigation. The statute also instructed the Florida Building Commission to develop and adopt within the Florida Building Code a means to incorporate recognized mitigation techniques for site-built, single-family residential structures constructed before the implementation of the Florida Building Code. This is the source for the FBC provisions in the Existing Building Code


      question answered by:

      Michael Goolsby
      Turnkey Roof Consulting, Inc.

  2. Vanessa Teran

    Good afternoon,
    This question is related to Method 1* “ Moment Based Tile Calculations per RAS 127” in High Velocity Hurricane Zone Uniform Roofing Application Form for Miami-Dade County , Could we use Zone 3 for HIP ROOFS as 3e and 3r, also, Zone 2n is missing from TABLE 7 — HIP ROOFS?.

    1. Claudia Abbona

      Yes, use 3e or 3r line item for Hip roof Zone 3. No 2n, in Hip Roofs.
      Question answered by: Gaspar Rodriguez MDC

      1. catherine A duffin

        Are Formal design calc required for tincap fastenting and tile calc.? if so is there a no cost tool that is acceptable to calculate for us?

  3. Dianne

    Is an additional layer of 30# and the tape on the plywood joints required on roofs over 2/12 pitch on all systems?

    1. Claudia Abbona

      Tape is not required in HVHZ, if you install tape it must be covered with #30 roof felt. the use of double #30 roof felt in HVHZ it is not required. The rest of the State does require it now. Thanks to Gaspar Rodriguez MDC

  4. Catherine Duffin

    Does the new 2020 FBC intend to provide FORMAL ENGINEERED tincap fastening patterns for field, perimeter's, corners, hips and ridges. at permit submission? Or is there a approved fastening pattern based upon height and exposure category, with no additional cost to contractor/building owner?

    1. Lyle Jacobs


      For adhered or mechanically attached insulation, anchor, and base sheets:


      ROOFING APPLICATION STANDARD (RAS) No. 117-20
      STANDARD REQUIREMENTS FOR BONDING OR MECHANICAL ATTACHMENT OF
      INSULATION PANELS AND MECHANICAL ATTACHMENT OF ANCHOR AND/OR
      BASE SHEETS TO SUBSTRATES
      1. Scope
      1.1 The standards set forth herein provide a means of determining proper attachment of anchor and/or base sheets and insulation panels.
      1.2 All testing shall be conducted by an approved testing agency. This roofing application standard has been developed to provide a responsive method of complying with the requirements of Chapters 15 and 16 (High- Velocity Hurricane Zones) of the Florida Building Code, Building. Compliance with the requirements, procedures and examples specified herein, when using the tables contained in RAS 128, do not require additional signed and sealed engineering design calculations. All other calculations must be prepared, signed and sealed by a Professional Engineer or Registered Architect.

      Note: Otherwise, design calculations are required.

      Also, it is possible that individual building departments may have “deemed to comply” attachment for small residential flat roofs, but the building code does not.

      Underlayments for asphalt shingles and concrete or clay roof tile are prescriptive:

      Underlayment shall be attached to a nailable deck in a grid pattern of 12 inches (305 mm) between the overlaps, with 6-inch (152 mm) spacing at the overlaps.

      Question answered by Mike Goolsby
      Turnkey Roof Consulting

  5. Kelsey McMenamy

    I have been receiving questions from roofers about the uplift requirements for underlayments under tile in the HVHZ zones. It is my understanding that for Non-HVHZ, the FRSA/TRI manual and R301.2.1.3 is used to determine the wind uplift requirement, which is then compared to the underlayment manufacturer's published FBC Non-HVHZ approvals to find an assembly that meets the uplift pressures. However, the M-D NOAs and FBC HVHZ approvals do not publish uplift pressures with their assembly approvals. This is because the weakest link is in the required nailed 30#. The FBC Sections 1518.2, 1518.3 and 1518.4 indicate requirements for 30# securement, but do not indicate what uplift pressure the specified fastening achieves, and doesn't indicate if it needs to be extrapolated at the ridges and perimeters/corners. Therefore, it seems that a roof system will be installed to code with any approved system (as listed in the NOAs of FBC HVHZ approvals) under tile as long as the 30# is nailed in accordance with FBC Sections 1518.2, 1518.3 and 1518.4, despite not having an uplift pressure rating. Please confirm. If this is not the case, please indicate how to determine the allowable uplift pressure of a system with an NOA since the NOAs do not list MDPs for underlayments. Thank you!

  6. Claudia Abbona

    There is no requirements for the uplift on tile system underlayment. Only the prescriptive method of attachment provided in the FBC HWVZ. (Per David Fuentes MDC)


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