Ice and water shield is a self-adhering waterproof membrane that goes on the roof deck in places where water is most likely to get in. It has a sticky backing, so it bonds to the deck and, in the better-installed cases, seals around the nails driven through it. The name comes from the problem it was designed for: water backing up under shingles from ice dams. It is used by installers in a variety of other spots as well.
How is it different from regular underlayment?
Regular underlayment, whether felt or synthetic, is rolled out and fastened, and its job is to be a secondary water barrier across the whole roof. Ice and water shield is a rubberized or modified membrane that sticks down, so it is generally used in selected areas rather than everywhere. For the broad background, start with what is underlayment. For a side-by-side look, see ice and water shield vs synthetic underlayment.
| Feature | Ice and water shield | Standard underlayment |
|---|---|---|
| How it attaches | Self-adhering | Mechanically fastened |
| Seals around nails | Designed to, per manufacturers | Generally does not |
| Typical coverage | Selected areas | Whole roof |
| Handling | Sticky; needs careful placement | Rolls out and is nailed down |
Where is it used?
Installers and manufacturers commonly point to areas like these:
- Eaves. Along the lower edge, where ice dams form in cold climates and where water can back up.
- Valleys. The channel where two slopes meet; see what is a roof valley.
- Around penetrations. Chimneys, skylights, vent pipes and similar spots.
- Along wall intersections. Where a roof meets a vertical wall.
- Low-slope areas. Some low-slope sections call for extra protection; see our guide low-slope roofs and underlayment.
Where it is required, recommended or optional comes from the manufacturer's instructions and local requirements, which vary by city and county. Ask your building department or your roofer.
Does it matter in Oklahoma?
Maybe, and it depends on the house. Oklahoma winters are mixed: some years bring ice storms and hard freezes, and many do not, and ice dams are more of a northern problem. That does not make the product irrelevant here. Installers use it in valleys and around penetrations for reasons that have nothing to do with ice, because those are the places that leak, and some also use it at the eaves for protection from wind-driven rain and freeze-thaw cycles. Whether it is worth including on your roof is a decision for you and your roofer, based on roof shape and the house.
Our crews take the view that valleys and penetrations are the places to spend extra care, and that is our practice, not a rule for every house. Ask your roofer to point out on a drawing or in the written scope where it would go and why.
Is it a replacement for flashing or good installation?
No. It is a backup layer. It does not replace correct shingle installation, flashing, or drip edge. Think of it as extra insurance against the roof's most vulnerable seams, not as a shortcut. For how those parts fit together, read what a roof replacement includes.
Questions to ask your roofer
- Where on my roof will self-adhering membrane be used, and why there?
- Which product is it, and does it meet the shingle manufacturer's requirements?
- Is it included in the estimate or an add-on?
- How is the rest of the roof protected, with synthetic or felt?
- Does the shingle warranty have any conditions tied to underlayment?
Frequently asked questions
Is ice and water shield only for ice? No. It is also used for leak-prone spots such as valleys and penetrations. Ice dams are the origin of the name.
Does a roof need it all over? Not typically. It is usually placed in selected areas, though some installers cover more. The scope should say.
Is it the same as synthetic underlayment? No. They are different products with different jobs. See the comparison and our page on synthetic underlayment vs felt.
Can it be installed in cold weather? Adhesive products can behave differently in cold or heat, and the manufacturer's instructions apply. Ask your roofer how they handle it.
Does it last forever? No product does. Its role is as a hidden layer under the shingles. Ask the manufacturer for the product's terms.
Does a roof with it never leak? No. It helps at vulnerable areas, but the whole system must be installed correctly.
Talk to us about your roof
Total Roof Protection OKC can inspect your roof and talk through where extra protection makes sense for your house. Call 405-415-5841 to set up an inspection. We describe the roof and the work we would propose; we do not promise outcomes.