Broward County HVHZ | Roofing

Backup Protection: Secondary Water Barrier

When shingles blow off, what catches the water? Your secondary water barrier is your last line of defense against water damage. Here is why it matters and how it works.

100%

HVHZ Required

Self-Seal

Around Nails

Sq Ft Protection

Calculate Roof Loads Compare Layers

Roof Layer Protection Demo

Shingles

Underlayment

SWB

Deck

BLOCKED

Normal State

Four layers protect your home: shingles, underlayment, SWB, and deck.

Underlayment Types

Know Your Roof Layers

Not all underlayments are created equal. Here is how they compare when your primary roof fails.

Felt Paper (15 or 30 lb)

Traditional tar paper. Stapled to deck. Cheap but has gaps at seams and staple holes let water through.

Hurricane Protection Poor

Nail Sealing No

HVHZ Compliant Alone No

Synthetic Underlayment

Plastic-based, stronger than felt. Better at resisting wind but still stapled and does not seal around nails.

Hurricane Protection Moderate

Nail Sealing No

HVHZ Compliant Alone No

Ice & Water Shield (SWB)

Self-adhering membrane. Sticks to deck and seals around every nail that goes through it. Your real protection.

Hurricane Protection Excellent

Nail Sealing Yes

HVHZ Compliant Yes

Installation Guide

Where to Install SWB in Broward

HVHZ code requires secondary water barrier in specific locations at minimum.

All Roof Edges (Eaves)

Install from edge to at least 24 inches up the roof slope. This is where wind-driven rain hits hardest.

All Valleys

Extend 24 inches on each side of the valley centerline. Water concentrates here during heavy rain.

Around All Penetrations

Pipes, vents, skylights - extend SWB at least 12 inches in all directions from the penetration.

Wall Intersections

Where roof meets walls, run SWB up the wall at least 4 inches and 24 inches onto the roof.

Hip and Ridge Lines

Install 12 inches on each side of hip and ridge lines where shingles are most likely to blow off.

Full Deck Coverage (Best)

Many contractors install SWB over the entire deck. More expensive but maximum protection.

Common Questions

Secondary Water Barrier FAQs

What is a secondary water barrier?

A secondary water barrier is a waterproof layer under your shingles or tiles that catches water if the primary roof covering is damaged. It is your backup protection when wind blows off shingles or debris punctures your roof. In Florida, it is usually self-adhering polymer modified bitumen membrane.

Is secondary water barrier required in Broward County?

Yes. The Florida Building Code requires secondary water barriers in the HVHZ. You can use self-adhering polymer modified bitumen tape at all joints, or a complete self-adhering membrane over the entire deck. Both methods meet code when properly installed.

What is the difference between felt paper and ice and water shield?

Felt paper (tar paper) is stapled to the deck and has gaps at seams. Ice and water shield is self-adhering and seals around nails. When shingles blow off, felt paper lets water through at staple holes and seams. Ice and water shield stays watertight even with exposed nail holes.

Where should secondary water barrier be installed?

In Broward County HVHZ, install it at minimum on all roof edges, valleys, around penetrations, and at wall intersections. Many contractors install it over the entire deck for complete protection. Code requires at least the vulnerable areas to be covered.