Snow Friction Coefficient for Commercial Roofing Materials

Abstract

Redistribution of snow loads on two adjacent buildings of different heights is addressed. The term slippery roofs is used but it is not defined. Measurements of friction between snow and commercial roofing materials are carried out to help specify the term. In order to determine a static coefficient of friction, the Coulomb friction principle of measuring inclination increase until specimen movement begins is applied. A test apparatus is designed and produced. Single-ply roofing materials such as membranes made of polyvinyl chloride (PVC), thermoplastic polyolefin (TPO), ethylene propylene diene monomer (EPDM), and modified bitumen (MB), as well as painted industrial metal profile specimens are tested. Snow specimens from fresh snow are prepared and tests are carried out under laboratory conditions. For the given conditions, although deviating from full-scale realistic conditions, snow samples slid at different angles depending on the roofing material type. Average values of sliding angle for PVC, TPO, EPDM, and MB membranes and metal sheet are determined to be 6°, 15°, 20°, 57°, and 22°, respectively. Based on the published provisions and given test conditions, commercial roofing materials can be categorized as slippery.