Yutzy Roofing Service LLC

How Does Flat Roof Drainage Compare to Non-flat Roofs? A Guide

There are many reasons that flat roofs are such a popular architectural design. The offbeat form serves a modern aesthetic that can easily add a luxury appeal to a business. And beyond that, you get a brand new function out of your business, a potential area to tread and make an extension of the interior.

In commercial settings, flat roofs make even more sense. They\’re cost-effective alternatives to pitched roofs, and with the greater HVAC demand in large commercial spaces, they give some much-needed real estate to hold these massive appliances.

The obvious problem is flat roof drainage, a significant drawback compared to pitched roofs. Without proper water redirection, the weather will accelerate wear and tear, leading to the breakdown of your roof and everything underneath it.

If you want all the advantages of a flat roof but are wondering how to solve the drainage problem, we\’ll explain everything you need to know about different drain options to install.

Why You Need Flat Roof Drainage

Flat roofs are more susceptible to damage because they can collect sitting water and debris like leaves and tree branches. Over time, these will wear down the roof, eventually opening up leaks that can damage the building\’s contents.

On commercial buildings, flat roof materials can exacerbate issues from poor drainage.

Although it\’s a practical building material, metal roof leakage is a common issue. It can contract and expand under temperature changes, and it\’s prone to rust. Without adequate drainage, rust can set in and open up leaks in no time.

No matter the roofing material, water, and abrasive debris can cause damage. And if you experience our Wisconsin winter weather, the added weight and damaging pressure of ice can be particularly hazardous. With improper drainage or any number of other defects, flat roof repair can become expensive in no time.

How Flat Roof Drainage Works

Flat roofs are not technically flat. They still need to drain, so they will have a slight slope, usually less than 10 degrees. The roof can be angled in several ways to create different drainage options.

Interior Drains

Interior drains are placed on a flat roof\’s inside area, with the roof sloping inward to direct water to it. The drain has a grate or other type of strainer to catch debris and prevent internal pipe clogs. The piping leads to an external gutter system that moves water away from the building.

These drains are ideal for large flat roofs often seen in commercial buildings. The drainage lines aren\’t exposed to weather and other damage factors, and the outside walls are protected from potential leakage issues. Internal drains also offer curb appeal because there is no exposed drainage system on the outside edge of the roof.

The many benefits of interior drains also raise the price of these systems. They\’re some of the most expensive you can install. And if you have a clog, which is common if you don\’t have adequate debris protection on a flat roof, repair jobs are much more expensive on an internal pipe than an exterior drain.


Gutters are the most common and cost-efficient option for many commercial buildings. Like residential gutters, these simple systems consist of a long trough that runs along the roof\’s edge to collect water and let it flow to a downspout. By redirecting water, it reduces wear on the walls and foundation.

A gutter system is a simple flat roof material to install, but it needs regular care to prevent roof leaks. Driving wind, ice, and debris can damage gutters and cause them to fail. They need frequent inspections to ensure they aren\’t leaking or collecting water that overflows.

The potential for damage is high, but the more pressing concern is clogging. In a long gutter system, there are numerous points where debris can accumulate and cause the gutter to fail. There are gutter covers to reduce buildup, but they still need regular inspections.


When it comes to flat roofs on commercial buildings, scuppers are simple, effective drainage options. A scupper is a wide opening on the edge of a flat roof that lets the water pour off. Builders sometimes attach downspouts to control the flow.

There are several advantages to scuppers. They\’re less expensive than interior drains, and, unlike gutters, they work on parapet walls. With a wide mouth, it\’s unlikely that they\’ll clog, so you won\’t have to worry about maintenance or repairs as often.

Scuppers are affordable, worry-free, and they can even be attractive if you design them well enough. Still, they aren\’t the best solution for every type of roof.

If the roof has a slight slope, scuppers won\’t be effective. They need water to flow towards them with a decent incline, especially if you deal with heavy rain. If your flat roof has a minor slope, you\’ll benefit more from interior drains.

Don\’t Forget Your Flat Roof\’s Drainage

It\’s easy for wear to set in on a commercial roof, but you can do your part to prevent severe damage by paying attention to your flat roof drainage system. With appropriate drainage that suits your building\’s design, you can rest easy that your roof and everything underneath it are safe and sound.

If you need help getting your roof in shape to handle the unpredictable Wisconsin weather, our team at Yutzy Roofing Service is here to help. For nearly 30 years, our family-owned business has been providing the premium roofing restoration work our commercial customers deserve. Contact us today to learn how we help you save time and money with quality roof repair.

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