Five Best Drainage Solutions for Flat Roofs

A flat roof does not rely on gravity to remove water as does slanting roofs. This is why flat roofs have unique drainage solutions.

Like any other roof, a poor drainage system will affect the integrity of your building. Luckily, many reasonable solutions will fit your specific needs. 

The flat roof drainage you choose affects the general appeal and performance of your roof. In this guide, we will be sharing five effective drainage solutions for homes in San Antonio.

But first …  

Why Do You Need Proper Drainage?

Poor drainage is one of the major risks to homes in the US. When the heavy rains begin, flat roofs are often exposed to water collection, which can bring down the roofs or lead to roof leaks. Aside from that, here are other reasons why you need to check the drainage of your house:

To Avoid Leaks From Water pooling on the Roof

Poor drainage can lead pooling of water on the roof, which can cause leaks or structural damage. This is not an issue for sloped roofs, as most water flows down automatically.

Possible Accumulation of Debris

Rainwater is one of many issues commercial buildings with flat roofs face. Debris, like twigs and leaves, also accumulates on the roof, which requires regular maintenance. A poor drainage system can make it worse.

Avoid Costly Damages to the Caulking and Tar

Debris and pooled water from heavy rain can damage the tar on rubber roofs. This will cost you a lot in repairs. You need proper flat roof drainage solutions installed to keep you from such problems.

Risky Extra Weight From Ice

When winter knocks, get ready to deal with your flat roof’s surface. If you have a reliable drainage solution, ice and water run smoothly through the downspouts to disperse on the ground.

It’s easier to remove water from a flat roof if you have a good drainage system. The goal is to ensure water runs smoothly off the roof without you having to climb there.

Five Drainage Solutions for Flat Roofs

The risk of leaving your flat roof without a proper drainage system is too high. However, choosing the wrong solution is even worse. So, here are the five most effective options.

Use Gutters

Gutter systems are the most popular option for those who need a cost-effective drainage solution. They are pretty simple, too – catching rainwater as it rolls off the roof’s edge and diverting it to a dispenser. They prevent the uncontrolled running of water down the wall, which could damage the sidings.

A gutter system will effectively drain water from the roof. They are most popular on sloped roofs but also on flat ones. They are affordable and quite easy to maintain.

However, one of the disadvantages of choosing gutters for your roof drainage systems is that they require consistent cleaning. Also, a gutter system is more prone to damage from harsh weather conditions like ice and heavy debris. Consider this before making your final decision.

Interior Drains

Interior drain systems are another popular option in the flat roofing industry. An excellent example of such a system is the drain in your shower or sink.

An interior drainage system needs to be placed in the roof areas that collect the most water. Drain and vent pipes are then used to dispense the water into gutters or the downspout on the wall.

Interior drain systems offer an effective drainage solution that connects to the built-in drainage system of your home. They protect your property’s walls and foundation from water damage.

In addition, the water pipes in your roof systems are protected from cracking and freezing since they are under the roof and walls. Aside from that, an interior drain system can be customized to improve your home’s curb appeal.

Among the disadvantages, these systems are quite expensive, especially when working on large square openings. Also, you may have to remove the entire system for roof replacements.


Invest in scuppers if you want water to drain automatically from your flat roof as if it were a pitched roof. A simple definition for such systems is smart drainage options. Ideally, rainwater drains through a perimeter wall and flows out over the ledge or a specially designed dispenser.

However, installing this system is quite tricky. You need to hire a contractor who can install it without causing structural damage to your commercial building. You can all call your local roofing experts for a free estimate.

Another limitation is that this drainage system can gather debris and leaves, leaving it blocked. Thus, it requires regular inspection – at least once every month to ensure the water flows freely. Your roofing experts will also advise you on the best approach.

Siphonic Drainage

This is also one of the best drainage systems for flat roofs, especially found on commercial buildings and large roofs. These systems rely on a vacuum pump to remove water from several drain openings. They apply hydroponic pressure, pulling water away from the roof’s surface.

These systems are ideal for large roofs that experience heavy rain or ice dams and require proper drainage. They don’t need electrical pumps, which makes them a low-cost option where large volumes of water are involved. Water is directed smoothly to your property’s foundation, leaving the roof clear.

One of this option’s biggest limitations is the installation cost. Also, they may take up more space leaving you with little for the HVAC equipment. However, they handle severe weather pretty well, which is why many property owners choose them.

Tapered Insulation

Another excellent way of dealing with drainage issues on a flat roof is adding some slope to it. Luckily, you can avoid dealing with major structural reformations for tapered insulation. The system comes in panels and is easy to install.

Apart from serving as an added protection layer for your roof, they effectively draw water off by letting it slide off the slope. Install them in areas with pooling water, and you can say goodbye to such issues.

You can use it together with one or more of the other solutions above. If you are unsure how to install them, call your local roofing effects, and they will help you set this cost-effective drainage solution in place.

A major limitation is that you have to combine it with another system, like gutters. Otherwise, water will flow down the siding, damaging it.

Let Professionals at Bison Roofing Do It

Most flat roofs come with built-in systems to remove moisture and handle the debris accumulating from the environment. Poor drainage will only do a little of this, forcing you to spend more on repairs and maintenance.

Hiring a qualified roofer will save you a lot of trouble. A team that understands how different flat roof systems work will ensure you never have to deal with clogged pipes or gutters. They will install the systems professionally and advise you on how to maintain them.

Bison Roofing is your number-one service in San Antonio and the surrounding regions. The company has been operating for more than 25 years, making it the most experienced company on the market. Your roof is in the safest hands.