Water Management 101: Flat Roof Drainage Solutions

As a commercial building owner or property manager, have you ever wondered if you need gutters, drains, or scuppers on a flat roof? It can be a difficult question to answer. A flat roof may not experience water runoff akin to a sloped roof. However, many other considerations are worth investigating before you write off the need for gutters, drains, or scuppers on your flat roofing system. We address the question, “Do you need gutters, drains, or scuppers on a  flat roof?”

Distinguishing Between Commercial Roof Gutters, Drains & Scuppers

Gutters

Typically, gutters are installed along the roof’s edges to gather water from the roof and transport it through the gutter channel to the downspout, where it can be safely moved away from the building. The roof requires a slight grade to enable water to enter the gutter freely without impediments or gravity limitations.

Drains

Commercial roof drains offer an effective means of internal water drainage off the roof surface. Internal drains are situated under the roof’s surface to collect water. Most commercial roofing systems are flat or low-slope. Drains help reduce the likelihood of ponding water that can cause a roof to age prematurely.

Scuppers

A scupper is a channel or opening in the roof’s sidewall. It is frequently installed with other water management systems, including gutters and downspouts. Depending on how it is constructed and connected, a scupper enables water to flow quickly and efficiently from the roof to the ground, gutter, or downspout.

Do You Need Gutters, Drains, Or Scuppers On A Flat Roof?

Pros & Cons Of Gutters

Benefits:

• A new gutter system is less expensive than a new drainage system.
• Attaching a gutter system is easier than installing a drainage system.
• High-quality gutter systems are durable and can withstand harsh conditions.

Challenges:

• A gutter system is visible and may not be aesthetically pleasing.
• Gutters often require routine cleaning, maintenance, and repairs.
• Without shields or guards, gutters can clog more easily than drains.

Pros & Cons Of Drains

Benefits:

• A quality drainage system can be the most efficient means of water runoff.
• An internal drainage system is “hidden,” so it is not visible to onlookers.
• Drain pipes are not generally susceptible to freezing during cold weather.

Challenges:

• Clogged drains may prevent the flow of water from the roof.
• Poor design or improper installation will make drains much less effective.
• Regular maintenance is necessary to avoid water ponding on the roof.

Pros & Cons Of Scuppers

Benefits:

• An overflow scupper may act as a backup for clogged drains or gutters.
• Scuppers are relatively simple to install on an existing commercial roof.
• Scuppers are very affordable compared to drains or gutters.

Challenges:

• Ineffective scuppers can create a damming effect, causing water to pool.
• Scuppers require an airtight seal to the downspout, or water will leak.
• Smaller or improperly installed scuppers are more likely to clog.