Important Things to Know About Flat Roofing Drainage Systems

Flat roofing systems, also known as low-slope roofing systems, are one of the best options for both commercial and residential properties. Their functional design allows water to drain and offers additional space that can be used for other purposes, like building a green roof.

However, these roofs often face challenges when it comes to water pooling as they lack a steep slope. This is why they need to be professionally inspected and maintained on a regular basis, to ensure the drainage works optimally. If you are thinking of installing a flat roof on your property, here are some important things to know before deciding on a drainage solution.

What You Need to Know About Flat Roofing Drainage Systems 

Here, we will walk you through important things you should know about flat roofing drainage systems to help you make an informed decision.

What considerations do flat roof drainage systems require? 

Flat Roofing Drainage Systems

Flat roofs generally have low slopes which make it harder for water to drain naturally, so the design relies on gravity. However, when property owners don’t consider their drainage solutions, the result is damaged interiors and reduced structural integrity of the roof. Over time this can lead to even more problems, including:

1. Debris accumulation, such as leaves and twigs.

2. Leaks close to or near other features of the roof such as the vent pipes and chimneys.

3. Damage to the tar and caulking from pooled water and debris buildup.

By not thinking about your flat roof drainage system, you put your property at unnecessary risk which will cost you both time and money to repair.

What are important factors to consider? 

While there are different types of flat roofing drainage systems, it’s important to choose the right type for your property to ensure it effectively drains rainwater. Here is a rundown of the factors to consider before choosing an option for your property.

  • Design Approach 

Whether your flat roof covers a small or large area, your first task is to determine how many downpipes and gutters are required and where they will be placed. This will ensure you address all of the areas, including those that often have pooling water. Ideally, you should choose downpipes and gutters of the same size for your entire roof as this will ensure the water drains at the same speed throughout the space.

  • Wind & Rainfall 

It’s a good idea to take a close look at your property’s layout and understand which sides are subject to more wind and which are protected. Before choosing a flat roof drainage system, it’s also important to consider the amount of precipitation your region receives. When this is done, you will be able to choose one that can handle the rainfall and high winds to which your roof will be subjected. It will also help you assess the capacity of rainwater drainage with which the system may have to cope. There is no point in investing in a system that cannot stand up to these elements.

  • Overflow Drains 

While you will most likely be thinking about the primary drain on your property, it’s worth taking into account secondary overflow drains for best results. These typically have their own set of pipes that allow water to drain without causing water buildup that will eventually lead to property damage.

  • Downpipe and Gutter Size 

To ensure your drainage remains functional, you must make sure that you choose suitable sizes of gutters and downpipes. This should be done as these elements control the flow rate of the rainfall which is necessary to ensure there is no stagnant or pooling water on your roof.

  • Hail 

If your region experiences hail storms accompanied or followed by rainfall, the hail can accumulate in the downpipes and gutters. This will reduce their effectiveness at draining water and cause pooling water. In this situation hail guards are recommended; these prevent hail from getting into the drainage system.

  • Serviceability 

Perhaps one of the most often overlooked factors when designing or installing flat roof drainage is the speed at which water is discharged from the roof. High speeds can result in water overshooting the gutter and, over time, can have disastrous consequences.

Our professional roofing contractors recommend a minimum slope length of 16 m for roofs with a width of 600 mm for drainage and should have a maximum inclination of 10 degrees. However, it’s still best to consider using baffle flashing.

  • Outlet 

The size and shape of the outlets you install will make a big difference in how well the drainage system works to eliminate water. And the smoother the transition it has from horizontal to vertical flow, the more water it will allow to flow into the downpipe.

Another great idea is to invest in a conical outlet to improve the flow of water which can easily be doubled by installing a sump. On the other hand, spigots and side outlets aren’t as efficient and may obstruct water flow into the gutter. This makes them an unsuitable option for commercial and industrial properties.

When it comes to choosing a flat roof drainage system for your property, it is well worth considering the factors mentioned here. By thinking about these elements beforehand, you will protect your property for years to come. If, however, you are still unsure about which type to choose, get in touch with professional roofers from top roofing companies. They will have the experience and skills to understand the needs of different properties and help you choose the right option.

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