In areas prone to ice forming along eaves, how many layers of underlayment cemented together are required for an ice barrier?

In areas susceptible to ice formation at the eaves, building codes establish that a minimum of two layers of underlayment cemented together are necessary for an effective ice barrier. This requirement is crucial because the ice barrier is designed to prevent water from backing up under roofing materials, which can lead to leaks and significant damage to the building's interior.

The two layers provide additional protection, ensuring that even if one layer were to fail due to wear or damage, the second layer remains intact to fend off potential water ingress. The adhesive between the layers enhances their reliability by creating a watertight seal, which is especially important in climates where ice dams can occur. Adequate installation of such barriers reflects an understanding of moisture management and structural integrity in commercial construction, aligning with standards.

Utilizing only one layer would not provide sufficient defense against ice-related issues, while layers greater than two are generally not required by code for standard applications, making two layers the correct and most effective choice for buildings in icy regions.