What is Ice and Water Shield?
Ice and water shield is a thick self-adhering peel-and-stick rubberized membrane installed under the shingles at the vulnerable parts of a roof, such as the eaves, valleys, sidewalls, and around penetrations. When the roof goes through an ice dam in winter or wind-driven rain in summer, water that gets past the shingles cannot continue through this membrane and into the roof deck. Ice and water shield is required by the International Residential Code on all asphalt shingle roofs in Northern Virginia and Maryland.
A cross-section of a residential roof eave showing the layered stack-up. The cyan layer sandwiched between the shingles and the underlayment is the ice and water shield, the last line of defense against water that gets past the shingles.
What is the difference between underlayment and ice and water shield?
Synthetic underlayment is a thin water-resistant sheet that covers the entire roof deck under the shingles. It is the first line of defense if a shingle blows off in a storm, but it is not actually waterproof; it is mechanically fastened with cap nails and sheds water like a raincoat.
Ice and water shield is a thick self-adhering peel-and-stick membrane (about 50 to 60 mils thick versus 10 mils for synthetic underlayment) that sticks directly to the roof deck. It is fully waterproof because it bonds to the wood substrate and seals around every nail driven through it. Where regular underlayment sheds water, ice and water shield STOPS water. Ice and water shield is installed only at the most vulnerable spots on the roof; regular underlayment covers everywhere else.
Where is ice and water shield required?
In Virginia and Maryland, the IRC requires ice and water shield at:
- The eaves, extending from the lowest edge of the roof to at least 24 inches inside the warm wall line (R905.1.2). This is the ice dam protection requirement and applies to climate zones where the average January temperature is at or below 25 degrees Fahrenheit. Northern Virginia and Maryland are both in this category.
- All valleys, beneath the valley flashing, extending at least 18 inches up each slope from the valley centerline.
- Roof-to-wall intersections where step flashing meets the wall, behind the step flashing.
- Around all penetrations: chimneys, plumbing vents, skylights, solar mounts, satellite dishes.
- Low-slope sections (anything under 4 in 12 pitch) where shingles are not really shedding water and the membrane carries more of the waterproofing load.
A good DH-style install covers approximately 30 percent of the total roof deck with ice and water shield. A budget install covers only the first 3 feet of the eaves, which is technically code-compliant but not best practice.
Does ice and water shield actually work?
Yes, and the test cases are well documented. The membrane was originally developed in the 1980s by W. R. Grace under the brand name Grace Ice and Water Shield specifically to solve the catastrophic ice damming problems in New England that were destroying ceilings every winter. After ice dam protection became required in colder climates in the 2000s, the rate of winter interior leak insurance claims dropped sharply in those regions.
The proof that it works is also visible during teardowns: when DH inspectors strip a 20-year-old roof and find the deck underneath the original eave ice and water shield is bone dry and the rest of the deck shows light staining from condensation, you can see exactly where the membrane stopped water from reaching the wood.
How much does ice and water shield cost?
Material cost is roughly $1.00 to $2.00 per square foot for residential-grade self-adhering membrane (about $200 to $400 per 200-square-foot roll). On a typical 30-square (3,000 square foot) Northern Virginia roof, ice and water shield at the eaves only adds about $300 to $500 in materials. Extending coverage to valleys, penetrations, and all roof-to-wall junctions adds another $200 to $400.
Labor is included in the base roofing price; ice and water shield is part of the underlayment scope, not a separate line item on most contractor quotes. If a contractor lists ice and water shield as an “upgrade” with an upcharge, that is a budget contractor padding the bid, not a real upsell.
Do you nail or staple ice and water shield?
Neither, in the sense that the membrane is self-adhering, meaning it bonds directly to the roof deck once the peel-off backing is removed. However, in practice, roofers do drive cap nails through the membrane at the top edge of each roll during installation to hold it in place while the adhesive sets, and shingles are then nailed THROUGH the membrane (the self-sealing rubberized layer seals around each shingle nail, which is the whole point).
Stapling alone (without the peel-off adhesive) is wrong. Some older membrane products were mechanically fastened only; modern code requires self-adhering peel-and-stick.
What DreamHome installs
DreamHome installs self-adhering 60-mil peel-and-stick ice and water shield on every roof replacement covering approximately 30 percent of the roof deck: the full eave from the edge to at least 36 inches inside the warm wall, every valley, every roof-to-wall junction, around every penetration, and on any roof section under a 4-in-12 pitch. This is included in the base price on every DH quote; it is never an upsell, and the coverage area is documented on the work order so the homeowner can verify what they paid for.
Red flags on someone else’s roof
- Ice and water shield listed as an “upgrade” or “premium option” with an upcharge. A budget contractor padding the bid. The IRC requires it; pricing it as optional is a misrepresentation.
- Coverage limited to “the first 3 feet” of the eave only. Code-minimum but not best practice. The full warm-wall coverage (typically 36 inches inside the wall line) is required for actual ice dam protection.
- No ice and water shield in the valleys. Very common omission on budget jobs. The valleys are where most leaks originate; skipping them defeats most of the protection.
- No ice and water shield around penetrations. Plumbing vents, skylights, and chimneys all need a self-adhering membrane wrapping them under the regular flashing.
- Stapled-only membrane. Mechanical-only fasteners with no peel-and-stick adhesive is an obsolete install method. Code requires self-adhering.