Does identification of wind load effect help in understanding mitigation measures to prevent damage to roofs?

by Nils Deacon, Manager, Inspections and Rating Services

High wind loads create serious effects on vulnerable areas of roofs. The following explanation of terms helps to provide a basis for understanding mitigation measures needed to protect roofs and other structural integrity issues associated with losses and claims.

Wind Uplift-Suction
Wind flowing over a roof creates low pressure above it (similar to an airplane wing), while higher pressure from inside the building pushes up. This creates a lifting force that can pull materials such as shingles, boards, and flashing off.

Pressure / Suction on Edges
Edges, corners, and ridges are exposed to the highest wind velocities and pressure differentials. This makes them vulnerable to detachment and damage.

Lateral Pressure
Horizontal wind pushes against walls that stress roof structures. This can cause tilting or shifting, destabilizing the roof.

Wind Driven Rain
Severe rain at high speeds can penetrate under compromised roofing. This causes interior water damage including rot and mold.

Debris Impact
Wind carries various objects like tree branches that cause punctures, dents, and cracking of roofing materials. ASCE, IBC, III

Upcoming Underwriters’ Corner articles will describe measures used to mitigate these factors to help address the roofing loss problem for the insurance industry.

DISCLAIMER: This information reflects the interpretation of MSO, Inc. with regard to NFPA Standards and Codes and other code sources. It does not represent these codes’ official position on the items discussed.