That is what is wrong.
Roof storm drain section.
The minimum slope the code allows is in 12 in.
In lieu of sizing the storm drainage system in accordance with section 1103 0 the roof drainage shall be permitted to be sized on the basis of controlled flow and storage of the storm water on the roof provided the following conditions are met.
A gravity drainage system on a flat roof differs from the gutter system you find on residential roofs in two key ways.
In a roof drainage system you have many components.
How ever 1106 2 states the vertical and horizontal storm drain piping shall be sized based on the flow rate through the roof drain but then states the flow rate in the storm drain piping shall not exceed that specified in table 1106 2.
The rationale for not requiring secondary drainage is that if positive drainage is provided that is adequate to drain the roof.
Size vertical storm drainage piping.
The sizing of the roof drainage system must consider all components.
The roof of a structure shall be designed for the storage of water where the storm drainage system is engineered for controlled flow.
Exception 1 of section 1511 1 states existing roofs do not have to meet the requirements of the code if positive drainage is provided.
The pipe sizing is only one component.
The international codes i codes are the widely accepted comprehensive set of model codes used in the us and abroad to help ensure the engineering of safe sustainable affordable and resilient structures.
A flat roof may use interior drains to collect water from the centre of the roof.
The rain storm the flow of rainwater on the roof surface the ability of the roof drain to move the water from the roof to the piping the vertical piping the horizontal piping and the connection to the point.
These drains are like the drain at the bottom of your shower except that the roof drain has a larger strainer to protect it from debris.
Ibc section 1503 4 roof drainage reads design and installation of roof drainage systems shall comply with section 1503 and the international plumbing code the applicable portion of the referenced ipc is chapter 11 section 11 storm drainage.
The international code council icc is a non profit organization dedicated to developing model codes and standards used in the design build and compliance process.
Cities based on inches per hour that may fall during a storm of one hour duration and a 100 year return period.
Size horizontal storm drainage piping.
Download free high quality cad drawings blocks and details of roof drains organized by masterformat.
The water from a 25 year frequency storm shall not be stored on the roof exceeding 24 hours.
Select number of roof drains and calculate the roof area sloped to each drain.
