Five Best Drainage Solutions for Flat Roofs

Dec 30, 2022

If your home or commercial building has a flat roof, you're probably already aware of its many benefits. Flat roofs are resistant to common roof hazards like hail, high winds, and animal damage. They can also make for an attractive architectural element when incorporated into a design that also features sloping roof sections.

The downside to flat roofing, however, is that it's vulnerable to water damage in a way that other roofing solutions aren't. Unlike sloped roofs, flat roofs can't rely on gravity alone to prevent water from pooling on their surfaces. This means they require a purpose-built flat roof drainage system for the task. Without one, they would be prone to costly leaks and structural damage.

The good news is that there are a variety of drainage options for your flat roof, each with their own benefits and drawbacks. To help you choose the right one, here's a guide to the five best flat roof drainage systems, and why they're such a vital part of keeping it in perfect condition.

The Critical Role of Flat Roof Drainage Systems

Although many people don't realize it, water can be a roof's biggest enemy. That's the reason that you won't find a roof anywhere in sight without some sort of gutter or drain system. It's also why people go through so much trouble to keep them from clogging. Water can cause underlying wood to rot, mold growth, and cause damaging leaks to enter the building's structure.

On a flat roof, the risk of water damage is multiplied. That's because a flat roof is prone to allowing water to pool up, which amplifies its' damaging effects. On top of that, pooling water on a flat roof is a cumulative problem – the longer it remains, the bigger the affected area gets.

Flat Roof Drainage Options

There are a few ways to make sure water drains away from the surface of a flat roof. Below are the five best roof drains for flat roofs:

1. Internal Drains

An interior drainage system makes use of several drains spaced across the surface of the roof, most commonly near its center. Since water tends to collect in the center of the roof, this can be an effective means of eliminating it. Each drain is connected to an unseen system of pipes or gutters beneath the surface of the roof. These pipes will route the water away from the building.

In most cases, each drain is protected by a screen or strainer that prevents any debris from entering the system. The fact that most of the system remains hidden under the roof's surface means they won't disrupt the visual appeal of the structure.

2. Scuppers

Of all of the methods used to prevent water buildup on flat roofs, there is one that is by far the simplest, and possibly the oldest. That method involves the use of scuppers, which is the technical term for an opening in the side wall of a structure at the same level as the flat roof's surface. They're the same types of openings that you would find lining the deck of wooden sailing ships to prevent seawater from flooding them.

To use scuppers as a flat roof drainage system, the roof must have a parapet or perimeter wall surrounding it. It must be adjusted so that the roof slopes gently towards the scuppers to drain away from the structure.

3. Gutters

Most flat roofs aren't exactly level. In fact, a roof is considered to be flat if its slope is no more than 10 degrees from the horizontal. Even though that difference isn't visible to the naked eye, it's enough to make gutter usage a possibility. In most cases, a flat roof will pitch in a single direction, where gutters can then catch the runoff to remove it.

This kind of drainage system is most common on small flat roofs, where water volume and buildup isn't extreme. It's also sometimes used in tandem with scuppers. This would be in situations where a retaining wall or parapet prevents direct access to the roof's edge.

4. Siphonic Drainage Systems

Found most often in commercial buildings, siphonic drainage systems use a gravity-induced vacuum pump to remove water via a series of drain openings. Such systems take advantage of hydroponic pressure to draw water away from the roof's surface at high speed, with no need for electrical pumps.Such systems are ideal for large roofs that experience frequent heavy rain. They have the capability of handling a large volume of water without being overwhelmed.

5. Tapered Insulation

Sometimes, the most effective way to drain water off of a flat roof is to add more of a slope to it. The good news is that this can be accomplished without any major structural overhaul in most situations. This can be done by installing tapered insulation on the surface of the roof. Tapered insulation is available in easy to install panels. They may be fitted together to introduce a slope that addresses areas of water pooling on a flat roof.

They also offer the added benefit of functioning as an added layer of protection for the roof's surface, while improving the building's energy efficiency at the same time. This approach is most common on commercial flat roofs, in concert with one or more of the above flat roof drainage solutions.

Leave it to the Professionals at Cloud Roofing!

As you can see, there's more than one way to keep water from pooling on the structure of your flat roof. We offer a variety of roofing repair and replacement services for issues like leaky roofs or other types of damage. Save money and make the right choice by contacting the experts at Cloud Roofing! Contact us today for your free estimate. We are the roofing experts in San Antonio and are happy to provide the best roofing solution for you!

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