A secondary water barrier is a sealed layer under the roof covering that keeps wind-driven rain out after shingles blow off, and Florida requires one on a single family reroof, most often as a 4 inch self-adhering tape over every joint in the deck.
Full answer:
CHAPTERS 0:00 The short answer 0:23 What the code says 0:54 The two methods 1:39 Where the rule came from 2:25 When it is triggered 2:56 What to ask your roofer
SOURCES - Florida Building Commission - HURRICANE MITIGATION RETROFITS, REROOF OPTIONS, Secondary Water Barrier, floridabuilding.org (PDF read first-hand 2026-09-23) - section 201.2 Roof secondary water barrier for site-built single family residential structures: a secondary water barrier shall be installed using one of the following methods when reroofing; method (a) all joints in roof sheathing or decking shall be covered with a minimum 4 in. wide strip of self-adhering polymer modified bitumen tape applied directly to the sheathing or decking, then covered with an approved underlayment system; method (b) the entire roof deck shall be covered with an approved self-adhering polymer modified bitumen cap sheet, with no additional underlayment required on top for new installations; exception: asphalt impregnated 30# felt installed with nails and tin-tabs as required for the HVHZ and covered with an approved self-adhering cap sheet or hot-mopped cap sheet is deemed to meet the requirement; definition: a water resistant roof underlayment layer or product that provides protection to the structure in the event the primary roof covering is damaged, removed, or penetrated by wind driven rain as the result of hurricane force winds; document written pursuant to the intent of HB 7057 - The Florida Senate - House Bill 7057 (2007), flsenate.gov (read 2026-09-23) - hurricane damage mitigation; effective June 12, 2007 - Envista Forensics - Florida Roofing Code Updates (read 2026-09-23) - prior to Hurricane Andrew in 1992 Florida had no uniform statewide building code and roofing regulations varied by jurisdiction; the 2001 Florida Building Code was implemented in 2002; the storms of 2004 and 2005 led to enhanced roof fastening guidelines, secondary water barrier requirements and improved underlayment performance standards
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By: Most Recommended Roofers Title: Why a Florida Reroof Now Needs a Sealed Layer Under the Shingles Sourced From: www.youtube.com/watch?v=XrVlD4o-OV4
