A Guide to Choosing the Ideal Drainage System for Flat Roof in Multifamily Property

Drainage System for Flat Roof

A flat roof has many architectural characteristics that make it a preferred choice of many multifamily property owners. The roof is ideal for areas that don’t experience heavy rainfall and moisture. For optimum utilization of space, multifamily unit owners can also create a rooftop garden or seating area on the flat roof. With these advantages, however, comes a disadvantage -inadequate drainage. Flat roofs can not slide water down like a sloped roof, which means a pool created on a rainy day. If the water stays for a long period, this would result in roof leaks, debris collection, and seepage, which will increase the maintenance cost of multifamily roofing services. An appropriate drainage system could be a solution to the problem, provided you choose the right type of drainage.

In this blog post, we discuss the three common drainage systems for a flat roof.


A scupper is an opening created on the sides of the walls to let excess water drain from the roof. The extra water goes into downspouts or gutters with the help of conduction heads. You can combine downspouts and gutters with the scupper to let the water flow in a specific direction. If you don’t want to use downspouts and gutters, ensure that the spout of the scupper extends past the wall of the building, so that it doesn’t damage the paint.

Related Post: Signs of Roof Damage

Internal Drain

It is a common option for multifamily buildings, where the drainage pipes are placed under the roof and in walls. The pipes are usually fitted at the center of the roof or an area where the water collects. There is a strainer in the internal drain to collect debris and prevent any clogging.


Also called as conductor pipe, a gutter is a trough that is fitted underneath the edge of the roof for carrying the excess water. Before you opt for a gutter, make sure that the roof has a slight gradient for directing the water. Most gutters are made of vinyl, galvanized steel and aluminum. They should be regularly cleaned to ensure there’s no blockage because of debris.

Final Words
A proper drainage system for the flat roof will increase the life of the multifamily property and reduce roof maintenance cost.

Make sure that you hire a reputable commercial roofing contractor to fix water logging issue on the flat roof. The professional will perform roof analysis and inspection to decide the type of drainage system that will be ideal for your multifamily property.