Why our new roofs include ice and water shield

Your roof is more than the shingles you see from the street. When you are comparing roof replacement quotes, it helps to know what goes underneath them, and one layer we never leave out is ice and water shield. Here is what it is, where it goes, why it matters in Tennessee even in a mild winter, and how it fits into the rest of the roofing system.

The layers of a shingle roof

From the attic up, a typical shingle roof is built in layers, and each one has a job:

• The roof deck: the plywood or OSB sheathing you see from inside the attic, which everything else is fastened to.
• Underlayment: a layer covering the whole deck between the wood and the shingles, as a backup if water gets past the shingles.
• Ice and water shield: a self-adhering membrane added at the spots where leaks are most likely.
• Shingles: the visible layer that sheds most of the water and takes the sun, wind and hail.
• Flashing and vents: metal at walls, chimneys and valleys, plus the vents that let the attic breathe.

Felt, synthetic underlayment and ice and water shield

Not every roofer uses the same underlayment. Some still use only felt paper, which is the cheapest and least protective option. Others use a synthetic underlayment, which comes in several grades, all of them better than felt. Professional roofers who want a replacement to last add an ice and water shield barrier on top of that at the vulnerable areas of the roof.

The difference is that ice and water shield sticks directly to the deck and seals itself around the nails driven through it, much like a rubber washer around a screw. Felt and most synthetics simply lie on the deck, so every nail hole is a small opening if water gets behind the shingles.

Why ice and water shield matters in Tennessee

You may not think of Nashville or Knoxville as ice country, but we get plenty of rain, and the wind often drives it sideways under shingle edges. Gutters clogged with leaves can back water up under the first courses of shingles. And a few times each winter, snow and the freeze-thaw cycle turn into an ice event, where ice dams can push water back up the roof.

GAF, whose roofing systems we install, describes its StormGuard leak barrier as protection against leaks from water backing up in gutters, wind-driven rain and ice dams, and notes that in warmer Southern regions these products mainly help protect against wind-driven rain. That is exactly the kind of weather our roofs see.

Where we install ice and water shield

Mobley Brothers Roofing & Renovation installs GAF's StormGuard ice and water shield where water is most likely to work its way in:

• In the valleys, where two roof slopes meet and water runs heaviest.
• Along the eaves, where gutters can back up and ice can form.
• Along the rakes, the sloped edges that catch wind-driven rain.
• Around chimneys, where the roof meets masonry.

Once the shingles go on top, the membrane seals around each nail and closes the path water would otherwise take into the deck.

What ice and water shield does not do

Ice and water shield does not stop ice from forming, and it is not a substitute for good shingles, flashing and drainage. Ice dams start with heat escaping into the attic and melting snow on the roof, so attic insulation and ventilation matter just as much. Our post on the vital role of your attic insulation explains how those pieces work together.

Part of a complete GAF roofing system

When we give you a free quote for a roof replacement, we quote a complete GAF roofing system, and that includes ice and water shield. As a GAF Master Elite residential contractor, we can offer GAF enhanced warranties: up to 50 years of coverage on qualifying new-roof installations, including up to 25 years of workmanship coverage through the GAF Golden Pledge, with the terms in your written proposal. If you are weighing materials, our architectural shingle roofing page covers the shingle side of the system.

Questions homeowners ask about ice and water shield

Do I need ice and water shield in Tennessee?

We think so. Our winters are mild compared with the North, but wind-driven rain, backed-up gutters and the occasional ice storm all test the same vulnerable spots, and the membrane costs little compared with repairing a rotted deck.

Can ice and water shield be added without a new roof?

Not on its own, because it goes under the shingles. It is installed during a replacement, or when a section such as a valley is re-roofed as part of a repair. If you have an active leak, our roof leak repair team can find the source first.

Is ice and water shield the same as underlayment?

No. Underlayment covers the whole deck; ice and water shield is a heavier, self-sealing membrane added at the valleys, eaves, rakes and around chimneys.

Talk to us about your roof

If you are planning a roof replacement or want to know what is under your current shingles, we are happy to explain it. For a replacement, we measure your roof from satellite imagery, send a written proposal, and look at the roof in person before install day, or sooner on request. Both offices are A+ rated by the Better Business Bureau in Lebanon and Knoxville. Call our Lebanon office at (615) 455-3131 for Middle Tennessee or our Knoxville office at (865) 205-0800 for East Tennessee, or request a free estimate online.