(Roof overhang”+wall depth”+24”) ➗ (cos(roof pitch in degrees)) 🟰inches of Ice&Water Barrier
Ice & Water Barrier Calculator
Find out how much ice and water barrier you need along your eave.
Enter your values above to see your result.
Diagram updates as you enter values.
This calculator provides an estimate. Consult a licensed roofing contractor for final measurements.
What is Ice & Water Barrier
While it's hidden beneath the surface, ice & water barrier plays an important role in protecting homes and businesses from the elements.
🔨 Installed beneath roofing materials to provide an extra layer of protection where water is most likely to penetrate.
💧 Creates a watertight seal around nails and fasteners, helping reduce the risk of leaks and moisture intrusion.
🏠 Protects vulnerable areas of the roof, including eaves, valleys and other locations where water tends to collect or back up.
How to calculate Ice & Water Barrier
Understanding the "why" behind roofing materials is just as important as understanding the materials themselves.
📏 How much ice & water barrier does a roof actually need?
🏠 A real-world example helps show how coverage is determined and why every roof may require a different amount of material.
💧 Proper calculations help ensure vulnerable areas receive the protection they need without unnecessary waste or guesswork.
Amount of Ice & Water Barrier installed not only changes from structure to structure but also changes based on area of structure it is being installed. We know that to meet code minimums almost all homes require 6’ at the eaves and 3’ in the valleys. That’s the minimum. That said there are many homes that require even more pending structure design. This home has a fairly common front porch overhang. Because the additional overhang it requires additional linear inches of ice barrier to meet minimums required by code.
What is the lowest steepness we can still install shingles?
Shingles can be installed down to a 2:12 pitch but when below a 4:12 pitch the underlayment needs special attention. This customer wanted to go with a higher quality Ice barrier. Grace Ice&Water barrier is known for its extreme adhesion and gasket like seal of the roof deck. Vulnerable areas for water backup include eaves, valleys, flashing areas and of course today’s topic, roof pitches less than 4:12 pitch. In areas where the roof pitch (steepness of the roof) is less than 4 inches of rise for every 12 inches of run, Ice&Water Barrier must be installed over the entire roof deck. While leaks won’t happen without it immediately; as the roof systems ages water backup causing leaks will become more likely. By securing not only your first layer of protection but also your second, we can extend the life of the same roof by years or even decades.
