Ice & Water Shield (Self-Adhered Membrane)
Ice and water shield is a self-adhered bituminous membrane applied to roof decking in vulnerable areas — eaves, valleys, and penetrations — to prevent leaks from ice dams and wind-driven rain. Required by code in cold climates at eaves.
Fast Facts
- What Is It?
- Rubberized asphalt membrane with polyethylene film backing that self-seals around nail penetrations. Applied directly to clean, dry sheathing.
- Common Uses
- Eaves (ice dam protection), valleys, around chimneys and skylights, low-slope transitions, and any area prone to water pooling or wind-driven rain.
- Cost Range
- $100–$180 per roll (1–2 squares coverage); $1.00–$2.50/sq ft material only.
- Durability
- Service life matches the roof — 30–50+ years under roofing material. UV exposure limited to 30–90 days.
Specifications
| Property | Value |
|---|---|
| Standard | ASTM D1970 — Self-Adhering Polymer Modified Bituminous Sheet Materials |
| Thickness | 40–60 mils (1.0–1.5 mm) |
| Width × Length | 36" × 65' (typical) = ~2 squares per roll |
| Self-Seal Temp | 40°F minimum for proper adhesion; use primer below 40°F |
| Vapor Permeance | <0.1 perms (essentially a vapor barrier) |
| Nail Sealability | Self-seals around 10d–12d roofing nails driven through membrane |
How Ice Dams Cause Leaks
Ice dams form when heat loss through the roof melts snow on the upper roof, which refreezes at the colder eaves. The growing ice ridge traps meltwater behind it, which backs up under shingles. Since shingles are designed to shed water flowing downhill — not standing water — leaks penetrate at nail holes and shingle overlaps. Ice and water shield self-seals around these nail penetrations, preventing leaks even with standing water.
Required Locations
Code requires ice protection at eaves in areas where the mean January temperature is 25°F or below (essentially IECC Climate Zones 5–8). Best practice extends ice and water shield to valleys, around skylights and chimneys, at dormer transitions, and at wall-to-roof intersections — anywhere water concentrates or changes direction.
Frequently Asked Questions
How far up the roof does ice and water shield need to go?
IRC R905.2.7.1 requires ice protection at least 24 inches inside the exterior wall line. In practice, this means 3–6 feet from the eave, depending on overhang depth. Many roofers run two full courses (6 feet) for extra protection in snow-country.
Can you use ice and water shield on the entire roof?
Yes, but it creates a vapor barrier over the entire deck, which can trap moisture in the sheathing if attic ventilation is inadequate. Full-coverage application is common on low-slope roofs (2:12–4:12) and in extreme wind zones but requires careful moisture management planning.
Related Guides
Also Consider
Synthetic Roof Underlayment
Synthetic roof underlayment is a woven or non-woven polypropylene or polyethylene sheet installed over roof sheathing before the final roofing material. It has largely replaced traditional #15 and #30 felt in new construction due to superior tear resistance, UV stability, and lighter weight.
Asphalt Shingles
Asphalt shingles are the most widely used residential roofing material in North America, covering roughly 75% of all homes. Available in 3-tab and architectural (dimensional/laminated) styles with 20–50 year warranties.
OSB (Oriented Strand Board)
Oriented strand board (OSB) is an engineered wood panel made from compressed wood strands bonded with waterproof resin. It is the most widely used structural sheathing panel in North American residential construction, offering uniform strength properties and lower cost than plywood.