Ice and Water Barriers for Your Roof

Roofing systems available in the market today are the product of years of innovation and engineering advancements. A roofing system is an integrated system of roof components that help a roof perform better against the elements.

There are three main layers of a roof system. Roof shingles are the most visible layer, but the other components, such as underlayment, ice and water barriers, ventilation, and insulation, all work together to help your roof do its job. Because they adhere to the roof deck, ice and water underlayment products create a waterproof barrier on your roof and help to keep moisture out.

Read on to learn more about this critical component in a roofing system.

How to Stop Water from Reaching the Roof Deck

The design of a roof has many purposes. Your roof offers protection from the elements, such as rain and snow. Rain lands on the surface of the roof (shingles) and runs down the roof’s slope into gutters, which direct the water away from the foundation through downspouts and drains. Rooftop snow eventually melts, following the same path.

Unfortunately, many situations can disrupt the ideal flow of water, and standing water is not a roof’s friend. Water that has pooled on the roof’s surface can cause various problems, eventually making its way under the shingles and into your home.

Roof Leaks

According to the National Roofing Contractors Association, certain conditions such as these can lead to roof leaks:

In an ideal world, leaves and seeds won’t land in your gutters, winds will remain at a gentle breeze and snow will only fall once a year. But that’s not the reality for many homes and roofs.

What are Ice and Water Barriers?

One practical solution is using an ice and water barrier underlayment below the shingles. Adhering directly to the roof decking, these barriers are impermeable, meaning they seal tightly around nails and keep moisture out.

Ice and water barriers offer added protection to your roof and can be used in the following areas:

Ice and water underlayment products create waterproof barriers that aren’t just for heavy rain and windstorms. There’s a good reason for the word “ice” in ice and water barrier.

Ice Dams: The Scourge of Winter

When you combine rooftop snow, heat loss from the attic and below-freezing temperatures, you have the exact recipe for an ice dam. The more snow and colder the temperature, the worse the outcome.

Let’s look at how an ice dam forms:

  1. Snow falls and collects on the roof.
  2. Snow melts due to rooftop heat transfer from the attic.
  3. The melted water flows down the roof’s surface.
  4. As it reaches the eaves, it refreezes, creating a solid wall of ice.
  5. Additional snowmelt begins to pool behind the ice dam.
Illustration comparing a low-risk vs high-risk roofs for ice damming

By eliminating any of the above issues, you can stop the ice dam from forming. While you can’t prevent snow from falling or water from flowing downhill, you can do something about increased snowmelt on your roof.

Prevention Strategies for Ice Dams

By making sure your attic is adequately insulated and ventilated, you can help prevent ice dams from forming in the first place.

Attic Ventilation

One of the primary causes of rooftop snowmelt is improper attic ventilation. The ideal is for the attic temperature to be the same as the exterior temperature. 

What causes elevated attic temperatures?

Both air leakage through the ceiling and minimal or insufficient insulation can contribute to elevated attic temperatures.

Properly located ventilation with sufficient net free area can help direct the warmed air away from the attic minimizing snowmelt. 

What is sufficient net free area?

Attics should have properly sized intake and exhaust vents positioned to provide balanced airflow. Vent sizes are expressed in net free vent area (NFVA) which accounts for any grilles, or filters to give you the actual open area for airflow for each vent.  

Why is insufficient or lack of attic ventilation a problem?

Insufficient ventilation that allows the attic to get warm can cause snow to melt and equally as important, a lack of ventilation can allow condensation to form on the interior side of the roof deck leading to wood rot and potential for mold growth.

How can I make sure my attic is properly ventilated?

There are many ways to properly ventilate your attic, including:

A balanced soffit and ridge vent system is recommended, but other options can provide proper ventilation also. 

Pro Tip: The Owens Corning Vent Calculator is a great tool to use to see if your home has enough roof ventilation and to determine the amount of ventilation you need.

You may also talk to a roofing contractor about ways to improve your ventilation.

Attic Insulation

With proper insulation levels and by air sealing the ceiling, you can help keep heat from your living spaces out of the attic:

Help! There’s an Ice Dam on My Roof

If you live in a region with frequent heavy snowfalls and frigid winter temperatures, ice dams are a seasonal risk. Ice and water barriers are your best defense for preventing water leaks caused by ice dams.

Ice and water barriers are:

Ice and water barriers are also installation-friendly, offering a slip-resistant surface to workers and suitable for cold weather applications. Owens Corning has eight specially designed ice and water barriers sure to meet the needs of any homeowner.

Did You Know: If you live in an area with an average January temperature below 20 degrees F, your building code probably requires a waterproofing barrier underneath the shingles along the eaves.

Leak Prevention 101

The bottom line is that roofing systems are constructed to direct the flow of water away from the roof’s surface and the home’s foundation. However, Nature’s elements, in the form of rain and snow, do their best to interfere with this process. Prevention strategies include adequate insulation and ventilation and installing an ice and water barrier beneath the shingles — directly on the roof decking.

If you’re missing one or more of these components, talk to an Owens Corning independent roofing contractor. They can inspect your roof and discuss solutions to prevent future ice dams and lessen the effects of any that occur.