Flat Roof Drainage System

A gravity drainage system on a flat roof differs from the gutter system you find on residential roofs in two key ways.

Flat roof drainage system.

There are three types of drain systems commonly used on flat roofs. Click to enlarge any image scupper drains become blocked by leaves or other debris through building drains upper right in the sketch become clogged internally and burst flooding the building or leaks occur around the drain itself where it penetrates the roof. Unlike other roofing types that are slanted or sloped to allow water to drain automatically flat roofs need a built in drainage system to help remove moisture and debris. In most cases a flat roof will pitch in a single direction where gutters can then catch the runoff to remove it.

The one challenge with flat roofing is ensuring proper drainage. There are roof coating products available if there isn t enough slant or slope to accomplish this. Poor drainage can lead to serious issues with flat roofing from leaks to structural damage. Although not commonly used anymore the eavestrough drainage system is a good option if you have an older large industrial or commercial flat roof.

A flat roof may use interior drains to collect water from the centre of the roof. Your building and location can help determine which drain will fit your roof needs. The most critical of these issues is the flat roof drainage systems. The sketch at left common leak points at flat roof drainage systems.

Each of these systems has its own pros and cons. Drainage ditches are created in the roof in the lower insulated areas. It s also sometimes used in tandem with scuppers. Of course the best designed flat roof has the correct amount of pitch to drain the water off naturally.

These ditches guide water toward the eavestroughs. The drainage pipes are placed under the roof and in the walls of the building. Internal drains constitute a common drainage system is most commercial buildings. Scuppers internal drains gutters.

Typically flat roof drainage systems fall into one of the following categories. This kind of drainage system is most common on small flat roofs where water volume and buildup isn t extreme.