Is ice and water shield required in the Treasure Valley?

Not on every roof. The building code calls for an ice barrier where ice has a history of forming along the eaves, and local inspectors decide how that applies. The foothills, Eagle, and Star see it expected more often than the valley floor.

Where does ice and water shield go on a roof?

Most important at the eaves, running past the exterior wall line, then valleys, plumbing vent pipes, chimneys, skylights, wall joints, and low slope sections.

How is ice and water shield different from regular underlayment?

It is a rubberized asphalt membrane that bonds to the deck and seals around nails, while felt or synthetic underlayment only sheds water. It is a targeted upgrade used with synthetic underlayment on the rest of the roof.

Is Ice and Water Shield Required on Roofs in the Treasure Valley?

Caleb Cook

8 minutes ago

3 min read

Ice and water shield is not required on every roof in the Treasure Valley, but the building code calls for an ice barrier wherever ice has a history of forming along the eaves, and many local inspectors treat the foothills and north facing slopes that way. Dodd Roofing and Exteriors installs it at the eaves, valleys, and roof penetrations on replacements because the added protection is a small part of the job compared with one winter of hidden leaks. Here is how the rule works and what to look for in your estimate.

What is ice and water shield and what does it do?

Ice and water shield is a rubberized asphalt membrane with a sticky back that bonds directly to the roof deck. When a nail passes through it, the membrane seals around the nail, so water that backs up under the shingles has nowhere to go. Regular felt or synthetic underlayment sheds water but does not seal. That difference matters at the spots where water sits or travels sideways, such as eaves, valleys, pipes, and chimneys.

Does the code actually require it in Boise, Meridian, and Nampa?

The International Residential Code, which Idaho cities adopt with local changes, calls for an ice barrier in areas with a history of ice forming along the eaves and causing water to back up. Because it is a local call, the answer depends on your city and sometimes your street. The valley floor around Boise, Meridian, Nampa, and Caldwell sees fewer freeze cycles than the foothills, and some inspectors do not require the barrier there. Eagle, Star, and the Boise foothills sit higher, hold snow longer, and see the barrier expected more often. Call your city building department or ask your roofer how your jurisdiction leans, and read your shingle manufacturer's installation instructions, since they spell out where underlayment is expected.

Where on the roof should it go?

The most important spot is the eave, running from the roof edge up past the exterior wall line, where melting snow refreezes. Valleys come next because they carry water from two roof planes. After that come the penetrations: plumbing vent pipes, chimneys, skylights, and the joint where a roof meets a vertical wall. Low slope sections deserve it too, since water drains slowly there.

Does the Treasure Valley really get enough winter for ice dams?

Boise sits near 2,700 feet and sees only around 20 inches of snow in a normal winter, but the swings matter more than the totals. A sunny afternoon in the 40s followed by a night in the teens melts snow over the warm part of the roof and refreezes it at the cold eave. Older North End and Boise Bench homes often have thin attic insulation that lets heat escape into the roof, which feeds the melt cycle. Newer Meridian and Star homes have deeper insulation but cut up rooflines with many valleys. Our guide on whether ice dams happen in the Treasure Valley covers the attic side of the problem.

How is it different from the rest of the underlayment?

Synthetic underlayment is the right choice for most of the roof because it handles sun and wind during installation better than felt. We compare the two in our post on synthetic versus felt underlayment. Think of ice and water shield as a targeted upgrade rather than a replacement for it. It also matters for metal edge details. Under the building code, drip edge goes beneath the underlayment at the eaves and over it at the rakes, which we cover in our drip edge guide.

What should you check on your roofing estimate?

Ask for three things in writing: where the ice barrier goes (eaves, valleys, penetrations), the product name, and whether it is included or priced as an add on. An estimate that says only underlayment leaves room for a bare felt eave. Confirm the work follows the shingle manufacturer's instructions, because shortcuts can affect the warranty. The amount used depends on how many feet of eave and valley your roof has, so a cut up roof uses more. If you want the work done before winter, we offer financing.

How do you get it done before the first hard freeze?

The sticky membrane bonds best on a clean, dry deck above roughly 40 degrees, and Boise nights are already dropping into the 30s and 20s, so the late fall window is closing. A free inspection will show whether your eaves and valleys already have a barrier and whether your attic is feeding ice at the edge. Call Dodd Roofing and Exteriors at (208) 295-9421 to schedule, and browse more answers in our homeowner guide library.