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!
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
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!
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.