Considering A Flat Roof? What Your Roofer Wants You To Know About Drainage

Flat roofing is far more common on commercial buildings than residential ones. As a result, many homeowners don't understand some of the key fundamentals that come with designing a flat roof. If you're building a home and you've envisioned a flat roof for the structure, it's important that you talk with a roofing contractor early in the design stages. Flat roofing needs to have drainage incorporated into the design, and it can be difficult to do so correctly when you lack the expertise. Here's a look at some drainage options to consider.

Subsurface Drainage

Perhaps the most common drainage solution for flat roofing is subsurface drains. This system consists of a series of channels installed below the surface of the roof, sort of like a French drain system around your foundation. Water seeps into those drainage channels and then flows out away from your home through the drain pipes that are connected to the system.

This is an ideal drainage solution because it allows you to maintain a flat roof without any concerns about needing a slope for proper water drainage. The drainage channels are invisible from the ground because they are below the surface, so they don't disrupt the appearance of your roof. And the water will be easily directed out away from your home so that you don't have to worry about foundation damage due to runoff.

Scupper Drainage

Scuppers are another option for flat roofing drainage. These systems involve installing channels along the very edge of the roofing to direct runoff to a downspout, much like gutters. Unlike gutters, however, scuppers are part of the roofing structure instead of being placed around the outside edge of the home. 

These are ideal for areas that see moderate rainfall and snow amounts. You may find some drainage challenges during periods of heavy rain, though. And it's important to note that the proper function of a scupper drainage system does require that the roof maintain a slight grade so that water runs down the slope to the scupper drains.


If you're not set on having a perfectly flat roof and you prefer the look of gutters versus built-in scupper drains, you should talk with a roofing contractor about incorporating enough of a slope to your roof for water to run off to a gutter system. Gutters can handle more excessive rainfall than scuppers, making them a better alternative in areas with heavy rainfall. They are often more affordable as well.

Talk with your roofing contractor about how much slope is necessary on your roof for a gutter system to provide sufficient drainage. In many cases, the slope is minimal enough that you won't visually notice it from the ground, which gives you the look of the flat roof that you're hoping for in your design.

These are the primary drainage options for a flat roof. Talk with your roofing company, such as Leon Construction, today for more help and information about flat roofing systems and the drainage structures that they require.