Ice and Water Shield Calculator
Find how far up the roof ice and water shield must run to reach past the inside of the wall, and how much you need.
Change the values and press Calculate to work out your own figures.
Enter the pitch, the overhang, the wall thickness and the eave length.
Show the working
- level run = overhang + wall + distance inside
- up the slope = run × √(1 + (pitch ÷ 12)²)
How to use it
Enter the pitch, the overhang, the wall thickness and the eave length.
Lengths can be decimals, fractions or tape entries such as 12' 6 1/2" (in feet or inches). Prices are optional.
Key facts
distance up the slope = (overhang + wall + distance inside) × √(1 + (pitch ÷ 12)²)
Code
Codes in cold climates commonly require the membrane from the eave to at least 24 in inside the exterior wall; some require more. Valleys are covered separately.
Questions
How far up a 6/12 roof must ice and water shield go?
3′ 10 15/16″ with a 12 in overhang and a 6 in wall.
Formulas
distance up the slope = (overhang + wall + distance inside) × √(1 + (pitch ÷ 12)²)
Sources
Limitations
- Material densities are typical values (the midpoint of the commonly published range); real loads vary with moisture, grading and compaction, so check with your supplier or type in their density.
- Tank results are the geometric volume; real tanks have wall thickness and fittings.