In roofing terminology, what does the term 'lap' refer to?

The term 'lap' in roofing terminology specifically refers to the part that overlaps or covers adjacent components, creating a weathertight seal. Proper lapping is critical in roofing applications to ensure that materials such as shingles, membranes, or underlayment are installed in a manner that directs water away from the building structure. This overlapping design helps prevent leaks and adds to the overall durability of the roofing system.

In roofing systems, components are often designed to overlap to manage water flow effectively and to protect underlying materials from moisture intrusion. When installed correctly, the lap forms an important barrier against wind-driven rain and other weather elements, contributing significantly to the roof’s integrity and longevity.