Ice & Water Shield: Where It Should—and Shouldn’t—Be Installed

When replacing a roof, some of the most important components are the ones homeowners never see. Ice and water shield is a perfect example. This self-adhering waterproof membrane is installed beneath the finished roofing material to provide additional protection in areas where leaks are most likely to occur.

But more isn’t always better. Understanding where ice and water shield should—and shouldn’t—be installed is an important part of building a roofing system that performs properly.

What Is Ice & Water Shield?

Ice and water shield is a self-adhered membrane installed directly to the roof deck. Unlike standard synthetic underlayment, it creates a highly water-resistant barrier and seals around properly driven roofing fasteners.

It’s especially valuable in Colorado and Utah, where roofs regularly experience snow, ice, wind-driven rain, freeze-thaw cycles, and rapidly changing weather conditions.

Where Should Ice & Water Shield Be Installed?

One of the most important locations is along the roof’s eaves.

During winter, heat escaping from a home can melt snow higher on the roof. That water travels downward and can refreeze near the colder edge of the roof, creating an ice dam. Water can then back up beneath the shingles.

Properly installed ice and water shield provides an additional layer of protection beneath the roofing system in this vulnerable area. Local building codes and manufacturer requirements determine how far the membrane must extend inside the exterior wall line.

Other common locations include:

Valleys: Roof valleys concentrate large amounts of water into a relatively small area, making them one of the most leak-prone parts of a roofing system.

Roof-to-wall transitions: Areas where a roof intersects a wall can benefit from additional waterproofing protection when incorporated correctly with the flashing system.

Penetrations: Chimneys, skylights, and certain roof penetrations may require or benefit from self-adhered membrane as part of the complete flashing assembly.

Where Shouldn’t It Be Installed?

A common misconception is that covering the entire roof deck with ice and water shield automatically creates a better roof.

That’s not necessarily true.

Standard ice and water membranes can have very low vapor permeability. Covering an entire roof deck can change how the roof assembly manages moisture. If the attic, insulation, air sealing, and ventilation aren’t designed appropriately, moisture may become trapped within the roof assembly.

There are situations where full-deck self-adhered membranes are specifically designed or required, particularly with certain roofing systems or high-wind applications. However, this should be part of an intentional roofing design—not simply a “more is better” decision.

It’s also important that ice and water shield doesn’t replace proper flashing. Applying membrane around a chimney or against a wall doesn’t eliminate the need for correctly installed step flashing, counterflashing, pipe flashing, or other required components.

Installation Matters as Much as Location

Even premium waterproofing products can fail when they’re installed incorrectly.

The roof deck should be properly prepared, overlaps need to follow manufacturer specifications, and the membrane must integrate correctly with underlayment, drip edge, flashing, and the finished roofing material.

At The Roofing Center, we believe a quality roof isn’t just about the shingles you can see. It’s about building a complete roofing system—from the roof deck and waterproofing to flashing, ventilation, and final roofing material.

Ice and water shield is excellent protection when it’s installed in the right places for the right reasons.