Miami-Dade HVHZ Secondary Water Barrier Requirements

Why this matters

Florida Statute 553.844 (the Mitigation requirement) and Florida Building Code (FBC) 2023 Section 1503.2 require a Secondary Water Resistance (SWR) layer on a re-roof when the existing covering is removed down to deck and the structure is located in the HVHZ or in a county that has adopted the SWR provision. Skipping or under-detailing the SWR is the single most common HVHZ roofing reinspection failure: the AHJ catches it at the in-progress inspection, after the deck nail pattern is fixed but before underlayment dry-in covers it. The fix is a full strip-and-redo of the SWR with a fresh sealed-seam pass. The crew lead and qualifier need a shared rulebook so the SWR detail is right on the first pass.

Where SWR applies

Per FBC 2023 Section 1503.2 and the underlying Statute 553.844, an SWR is required in HVHZ on any reroof down to bare deck. Outside HVHZ, the SWR is voluntary in most counties; some counties (Charlotte, Lee, Collier) have adopted the requirement by local amendment. Always check the AHJ's local amendments before assuming a non-HVHZ job is exempt.

The SWR is also required as part of the Florida Insurance Mitigation Inspection (Form OIR-B1-1802) credit for "SWR" - homeowners receive a hurricane premium discount when a qualified inspector documents the SWR is present. A correctly installed and photo-documented SWR pays the homeowner in lower premiums for the life of the roof.

Two acceptable SWR methods

Per FBC 2023 Section 1503.2.1, an SWR is one of:

1. A self-adhered polymer-modified bitumen (peel-and-stick) membrane applied directly to the sheathing, lapped a minimum of 4 inches on side laps and 6 inches on end laps, covering 100 percent of the deck. Underlayment is applied on top.

2. A taped-seam method: code-approved foil-faced or asphalt-impregnated sheathing tape (minimum 4 inches wide) applied directly over every sheathing joint, then underlayment over the entire deck.

Method 1 (full peel-and-stick) is the most common in HVHZ because it doubles as the storm underlayment on tile and metal jobs. Method 2 (taped seams plus underlayment) is cheaper but requires extra QC because every tape strip is a potential leak path if not pressed.

Approved SWR products

Each SWR membrane must carry a Miami-Dade NOA listing it specifically for the SWR application. Common approved products:

• GAF StormGuard Film-Surfaced Leak Barrier per NOA No. 23-0517.02
• CertainTeed WinterGuard HT per NOA No. 22-1108.07
• Owens Corning WeatherLock G Granular per NOA No. 23-0220.03
• Polyglass Polystick MTS per NOA No. 22-0517.01
• Henry Blueskin RF200 per NOA No. 22-0913.02

For Method 2 taping, accepted products include 3M All-Weather Flashing Tape 8067 and Polyglass Polytack. The tape NOA must explicitly list "SWR sheathing seam tape" use; generic flashing tape does not qualify.

Deck preparation rules

The peel-and-stick will not bond to dust, oil, ponding water, or oily kraft slipsheet residue. Per the NOA installation instructions, deck moisture content shall not exceed 19 percent measured by a pin meter. The deck must be swept of debris, fasteners countersunk, and any raised nail heads pulled or driven flush. Plywood that has delaminated or shows fungal staining gets replaced before the SWR goes down. New 19/32-inch sheathing carries an APA stamp visible on the face; orient the stamp face-down (toward attic) so the smoother face takes the membrane.

Primer is required on OSB per most NOAs; primer is optional on CDX plywood. Read the NOA installation section, not the data sheet, since the NOA is the controlling document for code compliance.

Lap and termination detail

Side laps shall be a minimum 4 inches with the upslope sheet lapping over the downslope sheet. End laps shall be a minimum 6 inches, staggered so no four-corner intersection occurs. Each lap is rolled with a hand roller or J-roller; finger pressure is not acceptable per most NOA installation instructions.

At the eave, the membrane wraps over the drip edge per FBC Section 1507.2.9 (drip edge under underlayment at the eave, over underlayment at the rake). At valleys, an additional 36-inch-wide membrane strip is laid down the centerline before the field run. At the ridge, sheets stop 1/2 inch short of the ridge centerline to allow ridge vent attachment without sealing closed the ventilation path.

Inspection-ready documentation

The in-progress AHJ inspection requires:

• Photo of bare deck with the nail pattern visible (typical 6-inch edge, 6-inch field per FBC Section 2304.10 unless engineered differently)
• Photo of every roll's label with the NOA-listed product name
• Photo of the lap pattern with a tape measure showing 4-inch side and 6-inch end
• Photo of the rolled laps at valleys and penetrations
• NOA cover sheet attached to the permit job folder

Without these, the inspector will lift sections of underlayment to verify the SWR detail. Save your crew the rework: photograph as you go.

Common failure modes

• Fishmouths at side laps from not rolling the seam
• Bare strip at the ridge where the membrane stops 6 inches short, leaving the ridge nail line exposed
• Taped seams not pressed (Method 2): tape lifts within 90 days
• SWR installed over dust or wet OSB: peels off in sheets within a season
• Wrong NOA cited on the permit (the underlayment NOA, not the SWR NOA): inspector rejects

References

1. Florida Building Code, 8th Edition (2023), Section 1503.2: Secondary Water Resistance, scope and installation methods.
2. Florida Statute 553.844, Windstorm Loss Mitigation, secondary water barrier requirement on HVHZ reroofs.
3. Florida Office of Insurance Regulation Form OIR-B1-1802, Uniform Mitigation Verification Inspection Form, SWR credit section.
4. Miami-Dade Product Control NOA application and search portal at miamidade.gov/pera (verify current NOA cover sheets).
5. FBC 2023 Section 1507.2.9: Drip edge installation requirements (eave under, rake over underlayment).
6. APA Engineered Wood Construction Guide, sheathing nail pattern reference for residential roof decking.