Scuppers As Primary Roof Drainage

A primary drainage system is designed to remove water from the roof as quickly as possible.

Scuppers as primary roof drainage.

See section 1107 for yourself. Scuppers are used to provide an outlet through parapet walls or gravel stops on flat and built up roofs to allow drainage of excess water. Firstly there is an explanation in the above referenced section for where and why a secondary roof drainage system must be provided. They can be used in conjunction with gutters and downspouts to divert the flow to the desired location.

Scuppers shall not have an opening dimension of less than 4 inches. Section 1503 4 2 scuppers when scuppers are used for secondary emergency overflow roof drainage the quantity size location and inlet elevation of the scuppers shall be sized to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by section 1611 1. It s very short and to the point. Scuppers can be installed to carry water into gutters or directly into downspouts through conductor heads.

The full flow capacity of a drain is not realized until the water reaches approximately 2 5 inches above the inlet in a four inch drain and 3 5 inches in a six inch drain. When scuppers are used for secondary emergency overflow roof drainage the quantity size location and inlet elevation of the scuppers shall be sized to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by section 1611 1.