Ice and water shield is a self-adhering, rubberized-asphalt membrane installed directly on the roof deck beneath shingles at eaves, valleys, and other leak-prone areas. Unlike standard felt or synthetic underlayment, it bonds tightly to the wood deck and seals itself around nail penetrations, so it stays watertight even after shingles are fastened through it. It's a distinct product from underlayment, not an upgraded version of it, and code requires it in specific locations rather than across an entire roof.
This is a companion piece to our article on what causes ice dams — that one covers how ice dams form and how to prevent them through attic insulation and ventilation. This article is about the membrane itself: what it's made of, where it goes, and why it's specified the way it is.
What the Membrane Is Actually Made Of
Ice and water shield is built from a rubberized (polymer-modified) asphalt compound laminated to a surface layer — typically a granulated or film surface for walkability — with a peel-and-stick adhesive backing. Installers roll it out, peel the release film, and press it directly onto the roof deck. No nails or staples are needed to hold it in place; the adhesive does that job.
The self-sealing property is the functional difference from every other underlayment product. When a roofer drives a nail through the membrane to fasten shingles above it, the rubberized asphalt compresses around the nail shank and closes the puncture, rather than leaving an open hole the way felt does. That's what lets it sit in a location where water can pool or back up under normal roof drainage — a felt or synthetic underlayment isn't rated to handle standing water, only sheeting water running downhill.
How It's Different From Felt and Synthetic Underlayment
Roofing felt (traditional 15# or 30# asphalt-saturated felt) and synthetic underlayment are both water-resistant layers stapled or nailed across the entire deck as a secondary barrier under shingles. They're designed to shed water that gets past the shingle layer during normal rain, not to withstand water sitting against them.
Ice and water shield is a waterproof membrane used only where water is expected to pool, back up, or concentrate — eaves during ice-dam season, valleys where two roof planes funnel runoff together, and around penetrations like chimneys and skylights where flashing seams are the most common leak points. It costs more per square foot than felt because it does a different job, not a better version of the same job. A roof deck typically has both: felt or synthetic underlayment across the field, and ice and water shield layered underneath it at the vulnerable zones.
Where Code Requires It — and Where Installers Add It Anyway
The 2021 International Residential Code requires an ice barrier at the eaves in regions with a history of ice-dam water backup, extending at least 24 inches inside the exterior wall line, with an additional 36 inches measured along the roof slope on roofs steeper than 8:12 pitch. (IRC R905.1.2) Colorado's freeze-thaw climate puts most Front Range jurisdictions squarely in that category, so eave coverage isn't optional here.
Beyond the code minimum, most Colorado Springs roofing crews also install it in valleys as standard practice, since valleys concentrate runoff from two roof planes and are one of the most common places for a shingle roof to leak regardless of ice. It's also standard around skylights, chimneys, and any roof penetration where flashing alone has a track record of failing over time.
Ice and Water Shield Installation and Pricing
On a typical Xactimate-scoped 20-square roof replacement in Colorado Springs, ice & water membrane runs about $1.85 per square foot, and covering the eaves and valleys on a standard roof adds roughly 600 to 900 square feet of membrane — about $1,100 to $1,700 in scope that a comparable roof at lower elevation, with less ice-dam history, wouldn't need. That's a separate line item from the felt or synthetic underlayment across the rest of the deck, which prices closer to $55.52 per square (100 sq ft) rather than by the square foot. Insurance-scoped estimates itemize both; some retail cash bids bundle them into a flat per-square price, which is worth asking about directly when comparing quotes.
Wondering whether your roof has adequate ice and water shield coverage? Call (719) 355-0648 or schedule a free inspection — we'll check eave, valley, and penetration coverage as part of every roof evaluation.
Frequently Asked Questions
Is ice and water shield the same as roofing felt?
No. Felt and synthetic underlayment are water-resistant, not waterproof, and they're mechanically fastened with staples or nails that leave open holes. Ice and water shield is a self-adhering, self-sealing membrane that bonds directly to the deck and closes around fastener penetrations, which is why code treats it as a separate, higher-performance product rather than a felt substitute.
Does every roof need ice and water shield across the whole surface?
No. Code requires it at specific vulnerable areas — eaves, valleys, and penetrations — not the full roof deck. Some roofers install it more broadly on low-slope sections or complex rooflines as an upgrade, but a standard architectural shingle roof only needs it at those designated zones.
Can ice and water shield be installed over an old membrane during a re-roof?
It shouldn't be. Old membrane can be brittle, have lost adhesion, or hide deck damage underneath. A proper tear-off removes the old layer down to the deck so the new self-adhering membrane bonds directly to sound wood, which is where its sealing performance actually comes from.
Does ice and water shield expire or wear out?
The membrane itself is durable and typically outlasts a single roofing system when installed correctly, but its performance depends on full adhesion to the deck. Heat cycling, improper installation, or a deck that was wet at install can degrade the bond over years, which is one reason a full tear-off and reinstall — not a shingle-only overlay — is the standard approach at re-roof time.