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Water is the nemesis of any roof, but it can be especially problematic for businesses or properties with flat roofs. The longer water sits on a surface, the quicker that surface deteriorates. A well-designed and adequately maintained commercial roof drainage system removes excess water and helps prevent water-related damage to a building.

Understanding the role of a drainage system in your roofing system’s overall design, as well as its key components, will make a difference when you’re waterproofing your business.

The Role of a Roof Drainage System

Whether it’s a business property or a home, roof drainage systems have the same goal — diverting water from the roof and building. Most excess water comes from rain. Controlling where the water flows prevents it from pooling on top of the structure or around the foundation, both of which can create a variety of water-related concerns.

Drains are usually located at the lowest point of a roof, where moisture tends to accumulate. However, many commercial properties have low-slope roofs that often can’t support natural runoff as well as a traditional pitched roof. That’s why it’s essential to invest in a built-in drainage system that effectively removes water from the surface. This is typically accomplished with a tapered roof system or a structurally sloped roof design.

Consequences of Improper Drainage on Your Business Property Roofing

Improper roof drainage can cause property damage and severely impact your business in many ways, resulting in costly repair bills.

Water Accumulation and Puddling / Ponding

Drainage, especially on a flat roof, prevents puddling or ponding. Without it, there’s no place for water to go, so it accumulates and becomes stagnant. The weight of this water places additional stress on the roofing materials, weakening them over time. Even concrete can fracture under the weight of standing water if too heavy for the design of the building. It should be noted that some roof systems can temporarily handle ponding water, but getting the water off of your roof system is the best course of action.

Roof Leaks and Interior Damage

Once a roof is compromised, the result is leakage. If a leak occurs in an area with a lot of puddling, you could end up with gallons of stagnant water pouring into your facility. Once water seeps through the roof, it begins damaging the interiors, leading to myriad problems that may include the following:

  • Soaked insulation
  • Mold and mildew
  • Compromised ceilings and rafters
  • Damaged paint and drywall
  • Faulty electrical wiring
  • Damage to equipment and products within

Structural Damage

Water is a persistent force. With time, it degrades even the strongest building materials, affecting your building’s structural integrity. Prolonged exposure to even minimal moisture can deteriorate wood, concrete and metal, compromising your property’s walls, floors and other essential structures.

Increased Maintenance Costs

Improper drainage could result in excessive moisture and leaks in and around your property, which can significantly increase your overall maintenance requirements. Here are a few potential issues you may face as a result:

  • Mold and mildew growth
  • Carpet and upholstery deterioration
  • Discolored or peeling paint
  • Damaged walls and flooring
  • Insect infestation
  • Damage to landscaping
  • Sticking doors and windows

Decreased Roof Life Span

The membranes used for most commercial flat roofs can have a decades-long life span. The damage caused by pooling water can cause your roofing material to deteriorate prematurely, which may leave you needing a total roof replacement.

Damage to Building Foundation

An effective roof drainage system does more than move water off your roof — it also protects your building’s foundation. Water accumulation around foundation walls can result in significant structural damage, such as bowing walls, cracks or even foundation sinking.

Key Components of an Effective Roof Drainage System

If you own a commercial building, it’s important to know the components that work together to redirect water away from your property’s roof. While drainage techniques can vary from building to building, an effective system will likely contain some of the following elements.


Gutters are among the most recognizable drainage solutions. Whether made from vinyl, aluminum or steel, they prevent rainwater from rolling off your roof uncontrolled, which could damage the sides, windows or foundation of your property. Gutters run horizontally along the roof’s edge, collecting water as it rolls down and diverting it into the downspout.


The downspout attaches to the gutter and moves water out and away from your property. This vertical pipe carries moisture from the gutters and moves it safely from the building so standing water does not pool around the foundation.

Drain Inlets and Outlets

A flat roof may require drain inlets and outlets to collect water and facilitate its flow away from your building. Roof drains work in much the same way as shower drains — as rain falls on the roof, gravity draws the water to the drain and down a system of pipes installed below the surface. The rain then travels through these pipes and safely pours into a gutter or downspout.


A scupper is a large square opening cut into the edge of the roof that is used as an outlet for water. This drainage solution is one of the most efficient options for commercial buildings with low-slope roofs.


Flat roofs are technically not flat — they feature a slight slope. A properly designed roof will allow your commercial building to support at least some degree of water runoff while still offering a surface flat enough to be traversed.

Choosing the Right Drainage System for Your Building

Drainage systems for flat roofs are not one-size-fits-all. Each property has its own needs, so you’ll need to evaluate a variety of factors before choosing the right drainage solution for your building. Some of the top considerations that go into this choice include the following:

  • Building and roof size
  • Roof type
  • Roofing material used
  • Local climate, including rainfall and the likelihood of snow or ice
  • Drain speed requirements
  • The amount or type of roof accessories, including vents and skylights
  • State standards and roofing building codes

Weighing these factors can feel daunting. If you’re not sure what you need, consult a commercial roofing expert who can help you choose the perfect drainage system for your structure.

Maintenance Tips for Roof Drainage Systems

Whether your roof drainage is brand-new, an older installation or a retrofit designed drain, prevention is the best way to keep the system in top shape. While it’s best to hire a professional roofing company to perform regular roof maintenance, it’s good to know a few basic practices you can handle on your own to help keep your roof drainage system operational:

  • Check for pooling water: Standing water could be a sign that there’s an issue with your drainage system.
  • Regular cleaning: Gutters and downspouts often become cluttered and clogged by debris like leaves and dirt. Check them regularly and clean them out.
  • Check for blockages: Run water through your drainage system to see if there is a blockage.
  • Inspect for wear and tear: Check for obvious signs of wear and tear, such as broken or missing fasteners or loose and sagging connections.
  • Seasonal preparation: Make sure your drainage system is ready to handle heavy snowstorms or spring showers by inspecting and cleaning your roof drainage system in spring and fall. You should also give it a once-over after severe weather.

Find Effective Commercial Roofing Solutions With Equity Builders Roofing

Keep your investments secure by safeguarding your roof and property from water damage with a suitable roof drainage system. When water is safely diverted from your commercial building, you avoid the risk of potential damage and costly repairs.

Not sure if your roof drainage is up for the job? Reach out to the experts at Equity Builders Roofing. We can come and inspect your commercial property for potential water-related problems. If you’re ready to upgrade your system, we can offer our professional recommendation on the right roof drainage for your needs. Contact us today to learn more.

Find Effective Commercial Roofing Solutions With Equity Builders Roofing