The IRC requires an ice barrier at the eaves of shingle roofs in areas where there has been a history of ice forming along the eaves, extending from the edge to at least 24 inches inside the exterior wall line (R905.1.2 in recent editions). Where it applies and the carrier estimate leaves it off, supplement it using eave length, overhang, and the required width.
- →Code ice barrier applies where local officials say ice dams occur
- →It extends at least 24 inches inside the exterior wall line
- →Valleys and penetrations often get it per manufacturer instructions
- →Quantity depends on overhang depth, not just eave length
Where it's required
Your local building department decides whether the ice barrier requirement applies. Many northern jurisdictions require it, while many southern ones don't. Separately, shingle manufacturers commonly call for self-adhered underlayment in valleys, and some warranties depend on it.
Calculating the quantity
- Take eave linear feet from the measurement report
- Measure overhang depth plus 24 inches past the wall line to get the required width
- Round the width up to full roll courses, since rolls are typically about 3 feet wide
- Add valley LF, and penetrations if called for
- Convert to squares or rolls as the estimate format requires
| Location | Basis | Support |
|---|---|---|
| Eaves | Adopted code ice barrier | Code section + local adoption |
| Valleys | Manufacturer instructions | Install guide page |
| Low-slope sections | Manufacturer / code underlayment rules | Pitch from report |
If the old roof didn't have an ice barrier, adding it may fall under code upgrade coverage. See code upgrade reimbursement. RoofGenius flags missing ice barrier lines against the measured eaves and valleys. See AI Supplements.