Ice and Water Shield: Where It Goes and How Much
Ice and water shield is a self-adhering, rubberized asphalt membrane installed under shingles in the places most likely to leak: eaves, valleys, and around chimneys, skylights, and vents. It seals around nails and protects the roof deck when ice dams or wind-driven rain push water under shingles. In cold climates, building codes commonly require an ice barrier along the eaves that extends from the roof edge to at least 24 inches inside the exterior wall line. Elsewhere, it is still widely used in valleys and at penetrations.
Asphalt tonnage calculator →Where it goes
| Location | Typical use |
|---|---|
| Eaves | Required by code in many cold regions; strongly recommended elsewhere |
| Valleys | Common best practice |
| Around chimneys, skylights, and vents | Common best practice |
| Low-slope sections | Often used for extra protection |
| Whole roof | Used in some high-wind or coastal areas |
How far up the eaves?
Many codes require the ice barrier to start at the eave edge and extend up the roof to a point at least 24 inches inside the exterior wall. With a deep overhang or low pitch, that may take two courses of membrane. Measure from the wall line, not the roof edge.
Roll sizes and coverage
A common roll is about 3 feet wide and about 65 to 75 feet long, roughly 200 square feet or 2 squares. Coverage varies by brand. For eaves, divide the eave length by the effective roll length after overlaps, and multiply by the number of courses needed. See how to measure a roof in squares.
Installation steps
- Install drip edge at the eaves first, then the membrane over it. See drip edge for shingles.
- Clean the deck of debris and dust.
- Peel and stick the membrane, rolling it smooth with no wrinkles.
- Overlap side laps about 3 inches and end laps about 6 inches, or per the manufacturer.
- In valleys, center a full-width piece in the valley.
- Cover with standard underlayment above the ice barrier area.
Install in moderate temperatures; the adhesive may not bond well in cold weather without warming.
Ice and water shield vs felt
Felt and synthetic underlayment shed water but do not seal around nails. Ice and water shield adheres to the deck and seals around fasteners, making it better in leak-prone areas. See asphalt roofing felt.
Low-slope roofs
Shingles are generally limited to slopes of 2:12 or steeper, and slopes between 2:12 and 4:12 need extra underlayment protection. See minimum roof pitch for asphalt shingles.
Ventilation note
Some manufacturers caution against covering an entire roof deck with membrane without adequate attic ventilation, since it can trap moisture. Follow manufacturer guidance.
Bottom line
Ice and water shield is a self-adhering membrane for eaves, valleys, and penetrations. In cold climates, codes often require it from the eave edge to 24 inches inside the wall line. A typical roll covers about 2 squares; install drip edge first at eaves and overlap seams as directed.
Questions people ask
Is ice and water shield required?
Many cold-climate codes require an ice barrier at the eaves.
How far up should ice and water shield go?
At least 24 inches inside the exterior wall line, measured up the roof.
Does ice and water shield go over or under drip edge?
At the eaves, over the drip edge.
How much does a roll of ice and water shield cover?
Often about 200 square feet, or 2 squares.
Related guides
- Asphalt Roofing Felt (Tar Paper): 15 lb vs 30 lb, Uses and Synthetic Alternatives
- Minimum Roof Pitch for Asphalt Shingles
- Drip Edge for Shingles: Placement, Types, and Code
- How to Measure a Roof in Squares: Pitch Factor Math
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