Tech Today

The importance of proper roof slope

Providing proper slope to aid in timely drainage is an important consideration when designing and installing quality, long-lasting, low-slope membrane roof assemblies.

This month, I will review guidelines and requirements for minimum roof slope applicable to low-slope membrane roof assemblies.

NRCA guidelines

In The NRCA Roofing and Waterproofing Manual, Fifth Edition, NRCA recommends all roofs be designed and built to have "positive drainage." NRCA defines positive drainage as the drainage condition in which consideration has been made during design for all loading deflections of a deck and additional roof slope has been provided to ensure drainage of a roof area within 48 hours following rainfall under conditions conducive to drying.