- Eave protection—
- Coverage height—
- Valleys—
- Coverage area (with waste)— sq ft
- Recommended productSelf-adhered ice barrier
- Estimated cost—
Material Summary
| Eave coverage area | — |
| Valley + penetration area | — |
| Total with waste | — |
| Rolls to buy | — |
| Estimated cost | — |
Ice Barrier Requirement by Climate
| Climate | Typical coverage |
|---|---|
| Warm / mild | Valleys and penetrations only |
| Moderate snow | 3 – 6 ft up from the eaves |
| Heavy snow | Extended eave protection, often 6 ft+ |
| Ice dam region | Double course at eaves plus valleys |
Roof Protection Comparison
| Product | Purpose |
|---|---|
| Asphalt felt | Basic, breathable underlayment protection |
| Synthetic underlayment | Lighter, tougher, better tear resistance |
| Ice & water shield | Self-adhered, fully waterproof, seals around fasteners |
How Much Ice and Water Shield Do I Need?
Ice and water shield is a self-adhered, fully waterproof membrane that goes under the shingles at the most leak-prone parts of a roof: the eaves, where ice dams back water up under the shingles, and the valleys, where two roof planes funnel heavy runoff. This calculator turns your roof into a roll count. Enter your eave and valley lengths, choose how far up the roof to cover, add waste for valleys and penetrations, and it returns the square footage, the number of rolls to buy, and the cost. The answer you want is rolls, not raw area.
Ice Barrier Code Requirements
In regions with a history of ice forming along the eaves, building codes require an ice barrier at the eaves. The standard rule is that the membrane must run from the lowest edge of the roof to a point at least 24 inches inside the exterior wall line, measured along the roof. On a typical overhang that is one 36-inch course; with deeper overhangs or low slopes it takes two courses, which is why heavy-snow and ice-dam regions usually call for a double course. Always check your local code, since the required distance and where it applies vary.
Valley and Penetration Coverage
Valleys should get full-length ice and water shield, one 36-inch-wide strip centered in the valley so it laps 18 inches up each side. Around penetrations like skylights, chimneys, and dormers, run the membrane up the walls and integrate it with step and counter flashing so water cannot sneak in at the joints. Even in warm climates where the eaves do not need protection, valleys and penetrations usually do, which is why the mild-climate setting still calculates for them.
Felt vs Synthetic vs Ice and Water Shield
These are not interchangeable. Asphalt felt and synthetic underlayment are water-resistant barriers that cover the whole deck and shed water, with synthetic being lighter and far more tear-resistant. Ice and water shield is different: it is a rubberized, self-adhering membrane that sticks to the deck and seals around nails, making it fully waterproof rather than just water-shedding. You use it at the vulnerable zones, eaves and valleys, and cover the rest of the roof with felt or synthetic underlayment.