North Carolina Building Contractor License Practice Exam

For roof slopes of 2 units in 12 units horizontal, what roofing underlayment is required?

1. 2 layers of felt

2. 1 layer of felt

3. Modified bitumen sheet

4. Ice barrier

The correct answer is: 1 layer of felt

A roof slope of 2 units in 12 units horizontal, which is approximately 16.67% or a 2:12 pitch, is considered a low slope. For low-slope roofs, proper underlayment is essential for ensuring water resistance and protecting the roof structure. In most building codes and roofing recommendations, roofing felt is commonly used as an underlayment for slopes below a certain threshold—in this case, 3:12. For a roof with a pitch of 2:12, a single layer of felt is typically adequate, as it provides a sufficient moisture barrier and allows for proper roof installation without risking water infiltration. Using one layer of felt helps to manage cost and installation complexity while still meeting building code requirements. Layers of felt or additional underlayment may be necessary for steeper slopes or specific roofing materials, but for the described slope, one layer is standard practice. This is why the correct answer is a single layer of felt.