In the HVHZ, the underlayment beneath your roof has its own wind-uplift requirement. This is separate from the field material's attachment and is often overlooked in non-HVHZ areas where the underlayment is treated as a single moisture-barrier element. In HVHZ work, the underlayment is structural; it must hold its own against wind forces.
What the code requires
The 2026 Florida Building Code, applied through the HVHZ appendix, requires that self-adhered underlayment systems used in the HVHZ pass specific uplift tests under the TAS 100 series and demonstrate continuous adhesion to the deck under sustained wind pressure.
The structured tables in the code specify the required uplift resistance for various zones (field, perimeter, corner) at various building heights and wind speed conditions.
What this means for product selection
Not every self-adhered underlayment is HVHZ-approved. The product must carry a current Miami-Dade NOA that explicitly references the HVHZ zones and the attachment pattern that achieves the required uplift performance.
Common HVHZ-approved underlayments include Polyglass Polystick TU Plus, GAF StormGuard, and Carlisle WIP. There are others. The verification is the NOA, not the brand reputation.
What this means for installation
The NOA specifies the substrate condition (typically clean, dry plywood or OSB at a specific moisture content), the application temperature range, the seam overlap, and the back-rolling or back-stripping requirements.
Each of these matters. An HVHZ underlayment installed on a substrate above the moisture limit, or at a temperature outside the application range, may not bond at the rated uplift performance. The roof can pass visual inspection and fail under wind load.
What inspectors check
The HVHZ inspection process specifically checks:
- The product's NOA is current
- The substrate condition matches the NOA requirements
- The seam overlap is as required
- The full coverage extends to the corner zones
- The flashing seal at penetrations and wall transitions is per the NOA
A dry-in inspection that does not check these items is not a meaningful inspection. We have walked some HVHZ projects where the dry-in was approved but the documentation did not actually verify what the code requires.
The practical implication
Three things to verify on your HVHZ roof:
- The underlayment product (name, manufacturer, NOA number) is in your closeout package.
- The installation conditions are documented (date installed, substrate condition, temperature).
- The dry-in inspection is signed off in writing by the county or city inspector, with reference to the NOA requirements.
If any of these is missing on your existing roof, your underlayment may be code-compliant in practice but you have no documentation. In the event of a wind-related claim, this can become a dispute.
Why this is worth knowing
Most homeowners never think about underlayment. In the HVHZ, the underlayment is the layer that matters most when a major storm hits. The visible roof material can fail, the underlayment can hold, and the home stays dry. Or the underlayment can also fail — and the home does not.
Specification, installation, and documentation matter more here than anywhere else in Florida.
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