What do the specifications on an ice and water shield data sheet mean?
Short answer. A good ice and water shield data sheet shows compliance with ASTM D1970, the standard for self-adhering steep roof underlayment, along with thickness, application temperature range, in-service temperature rating, UV exposure limit and surface type. Those numbers tell you whether a product suits a shingle valley, a hot metal roof or a cold-weather install.
The key specs
- ASTM D1970 compliance. The standard covers self-adhering polymer modified bitumen sheets used as steep roof underlayment for ice dam protection, with tests for thickness, strength, tear resistance, low-temperature flexibility, adhesion and sealing around nails. Codes reference it when they allow membrane as an ice barrier or valley lining.
- Thickness. Listed in mils. About 40 is standard; thicker products add durability and cost.
- Nail sealability. Whether the membrane seals around nail shanks driven through it, the property that makes it a barrier rather than ordinary underlayment.
- Application temperature. The minimum air and deck temperature for the adhesive to bond, often in the 40s for standard products and lower for cold-weather formulas.
- In-service temperature. The maximum the membrane tolerates once covered. High-temperature products rated around 250 degrees F or more are made for metal roofs.
- UV exposure limit. How many days it may sit uncovered, commonly about 30 to 120.
- Surface. Granular for shingle roofs and foot traction, smooth or film for metal and tile.
- Permeance. Essentially vapor-tight, which is why attic ventilation still matters.
- Code listings. Some data sheets cite code evaluation reports.
Matching the spec to the job
Shingle valleys and penetrations: a standard granular or smooth product. Metal roofs: high temperature, smooth surface, approved by the panel maker. Winter installs: a low-temperature formula, or wait for a warmer day. See ice and water shield in Georgia and metal roofing in Georgia.