North Carolina Building Contractor License Practice Exam

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What is required for proper valley installation in roofing?

A single layer of modified bitumen
Two layers of underlayment cemented together or modified bitumen sheet
Only metal valley linings
A minimum of one layer of felt

The correct answer is: Two layers of underlayment cemented together or modified bitumen sheet

For proper valley installation in roofing, using two layers of underlayment cemented together or a modified bitumen sheet is essential. This method ensures that the valley is adequately protected from water intrusion, which is a critical point in the roofing system where runoff from the roof meets. The dual layer of underlayment provides a robust barrier that reduces the risk of leaks and helps to manage water flow effectively. The integration of modified bitumen can also enhance the overall waterproofing capabilities because this material offers added durability and flexibility compared to standard felt. This is particularly important in valleys, which can experience heavier water flow during rainstorms. Ensuring that valley areas are double layered with a reliable material safeguards the structure underneath, promoting longevity and stability in the roofing system.