Positive Draininage On A Roof

Tapered systems can be part of the roof s insulation system and are key components of both bur and single membrane systems.

Positive draininage on a roof.

Well considered foundation design and its interface with surrounding soils combined with effective site drainage can eliminate most moisture problems that are typically found in basements. Positive drainage is created when you create surface drainage by grading an area so that water collects and flows to a lower elevation away from buildings structures. The term positive drainage is defined as the drainage condition in which consideration has been made for all loading deflections of the roof deck and additional roof slope has been provided to ensure drainage of the roof area within 48 hours of rainfall. Water adds significant weight to a building especially if the drains are clogged or poorly implemented.

Positive drainage conditions are created by routing water around deflections to lower points on the roof via tapered systems where the water can be evacuated. Nrca defines positive drainage as the drainage condition in which considera tion has been made during design for all loading deflections of a deck and additional roof slope has been pro vided to ensure drainage of a roof area within 48 hours following rainfall under conditions conducive to drying. Positive drainage noun the drainage condition in which consideration has been made during design for all loading deflections of the deck and additional roof slope has been provided to ensure drainage within 48 hours following rainfall during conditions conducive to drying. Architects must also take into account the weight of water on the roof including near the drainage areas.

Positive drainage should allow the water to drain off the roof 24 48 hours after it stops raining. In previous years tapered systems were created on site by cutting and shaping regular roof insulation components.