What Are Flat Roof Systems, and Which Option is Right For You?

Across the USA, flat roofs are becoming increasingly common — not just in apartment buildings and commercial properties but also in residential constructions. And for a good reason: Flat roofs are more affordable, easier to clean, and more energy efficient.

All roof elements — ventilation, insulation, an ice and water barrier, a felt underlayment, and the shingles — come together to make a roof system.

There are several types of flat roof systems, depending on the installation process and the roofing materials used. Each has its own pros and cons.

So, whether you’re looking at replacing your roof, or carrying out maintenance on an existing roof, let’s look at which flat roof system is best for your needs and the pros and cons of flat roof systems.

Types of Flat Roof Systems

Despite their name, the best flat roof systems aren’t entirely flat.

Usually made of synthetic rubber and asphalt, these roofs have a slight slope to drain water. Some come with waterproof membranes to prevent leakage, while others have thermal insulation capabilities to keep the heat out.

With so many options and materials to choose between, the best flat roof system depends on your needs, your budget, and factors like where you live and the type of construction you want to cover. Let’s look at some of the most popular roofing systems for flat roofs to understand more.

Thermoplastic Membrane Flat Roof System

This system consists of a single-ply layer of material that is made up of two thermoplastic materials and stuck to a polyester scrim for reinforcement. This single-ply is, in turn, fixed to a roof with screws and plates.

A thermoplastic membrane roof is made of two materials — polyvinyl chloride, or PVC, and thermoplastic olefin, or TPO.

Thermoplastic Membrane Flat Roof System

Roofs made out of PVC are easy to install and sturdy. They can last up to 20 years in the right conditions. Due to the harmful chemicals PVC releases, however, more modern thermoplastic membrane roofs are generally made with TPO.

A TPO flat roof system lasts just as long as its PVC counterpart — anywhere from 15-20 years. When it’s time to replace the sheeting of a TPO roof, it’s possible to recycle the old material. Additionally, roofs made with TPO are also known for their UV absorption and flame-resistant capabilities.

Pros and Cons of A TPO Roof System

What makes a TPO flat roof system worth it?

It’s cost-effective: Depending on the type of material used, the cost of a TPO roof system could slightly differ. But either way, it’s cheaper than most of its counterparts.

It’s easy to maintain: A TPO flat roof system is naturally resistant to mold growth, tears, and dirt. This means they need to be washed less.

It’s easy to install: TPO sheets are wider than other materials. This makes them easy to install and contributes to their low cost.

It’s energy efficient: Due to its strong UV resistance, TPO roofing can keep a building cool in summer by preventing heat build-up, significantly reducing air-conditioning costs.

Why isn’t TPO considered the best flat roof system?

It’s too new: So, while they seem like a promising option, they haven’t proven how durable they are just yet.

It’s prone to cracking: The top layer of a TPO roof is laminated, which can lead to cracks developing on the surface much faster than usual.

The quality isn’t consistent: There are several brands of TPO, each with its own quality assurances. This makes it hard to tell whether a TPO roof will last as long as it should.

Rubber Membrane Flat Roof System

This type of roof consists of a single-ply membrane made up of rubber. Also known as an ethylene propylene diene terpolymer (EPDM) roof, it comes in either black or white depending on whether installed in warmer or colder climates.

An EPDM flat roof is either glued down or anchored with adhesives or rocks and lasts about 25-30 years. Due to the ease of this roof installation process, it’s one of the best flat roof solutions if you’re looking to keep costs low.

Rubber Membrane Flat Roof System

Pros and Cons of an EPDM Flat Roof

Why is an EPDM roof considered the best residential flat roof system?

It’s exceptionally cost-effective: Most experts consider it the go-to option for anyone looking for a roofing system on a budget.

It’s eco-friendly: Besides offering UV protection, the material is ideal for rooftop gardens or even a flat roof solar mounting system.

It’s fire-resistant: In fact, the rubber used can even help slow a fire down.

It’s waterproof: Not only does this prevent leakage, but it also helps immensely when it’s time to install a flat roof drainage system.

So what’s wrong with an EPDM flat roof?

It’s prone to wear and tear: A non-reinforced EPDM flat roof is prone to shrinkage and damage and needs professional maintenance at least twice a year toward the end of its lifespan.

It isn’t very attractive: While very useful, rubber roofs aren’t the most aesthetically pleasing of all flat roofing options. To make it more appealing, you could also consider choosing between several flat roof decking systems.

Metal Flat Roof Systems

Metal flat roof systems are another popular option. Typically made with aluminum tin, copper, or steel, it involves fastening large metal sheets to the surface of a roof.  Known to last long and withstand most weather conditions, metal flat roof systems are ideal for dry and warm climates, as they reflect heat and moisture.

Pros and Cons Of Metal Flat Roofs

Why are metal flat roof systems considered one of the best flat roof solutions?

It lasts longer than other materials: Metal is unlikely to crack, split, or warp, so a metal roof can last up to 40-50 years. In fact, more high-end metal roofs are believed to last a whole lifetime.

It’s easy to install: The materials that make up a metal roof system are lightweight and come in panels that can be put in place quickly.

It’s good for the planet: Metal reflects heat instead of absorbing it, allowing people in warmer climates to save on cooling.

It’s weather resistant: It would take a lot of heavy wind and a severe storm to cause any damage to a metal roof, as they’re known to be highly resilient.

What could go wrong with metal flat roof systems?

They’re expensive: High-end metal flat roof systems could cost 5-10 times more than asphalt counterparts.

It’s noisy: While resilient, metal roofs can be quite noisy during stormy weather conditions.

It’s harder to install: Since metal contracts and expands depending on the weather, the panels must be put in place firmly by an expert.

It’s hard to walk on: Metal is slippery to walk on, especially when it is wet. To reduce the amount of water that stays on the surface, you could consider also installing a high-quality flat roof gutter system.

Metal Flat Roof Systems

Built-up Roofs

One of the most common roofing systems for flat roofs, built-up roofs have been around for over 100 years and are easy to identify with their tar or gravel finish.

In this system, multiple layers of asphalt are applied between ply sheets over a roof deck and finished off with a top layer of aggregate or gravel. The choice of how many layers depends on your budget, but each one adds to the roof’s lifespan.

Depending on the layers and the specific materials used, a built-up roof system could last anywhere between 15 to 30 years. It’s more commonly seen in warmer climates.

Pros and Cons of Built-up Roofs

Why are built-up roofs considered one of the best flat roof solutions?

It offers more grip: Due to its layer of gravel or aggregate, a built-up roof provides excellent traction, even during wet or snowy conditions.

It’s leak-proof: Since built-up roofs are entirely sealed, it would require immense wear before any drops of water can seep through. Ballasted built-up roofs also have no seams, unlike other flat roofing options.

It offers more protection: The multiple layers that make a built-up roof offer excellent protection from hail storms or falling branches.

It’s UV resistant: Much like the other flat roofing options, it is UV resistant, with the gravel acting as another layer of protection.

It’s easy to repair: Since each layer can be considered by itself, it’s easier to repair potential punctures or wear in a built-up roof

Where do built-up roofs fall flat?

It isn’t wind resistant: When faced with strong winds, the outermost layer of gravel can dislodge and fly off the roof, causing some damage.

It’s heavy: Multiple layers of gravel add significant weight to the top of a building. Before installing, a professional roofing contractor will consider whether the structure can take the weight of a built-up roof.

It’s hard to clean: As you’d imagine, it isn’t easy to brush off snow from a layer of gravel. If you live in a frigid climate, you might need to consider your options for flat roof snow melt systems.

It’s hard to install: A built-up roof system can be challenging to put in place, considering how much labor it requires for multiple layers to be added.

Built-up Roofs

Modified Bitumen Roofing System

Several experts consider Modified Bitumen roofing the best roofing system for flat roofs, similar to built-up roofing in that it’s also made up of several layers.

This system consists of an asphalt-based sheet comprising five layers — insulation, modified base sheet, modified bitumen membrane, an adhesive, and surfacing to provide UV protection.

This flat roofing option has been used in the United States since at least 1975 and is trusted by experts for its ability to withstand extreme weather conditions.

Pros and Cons of Modified Bitumen Roofing

Why do some consider it to be the best flat roof system?

It has a proven track record: This type of roofing system has been around for over 50 years and is trusted by most experts due to its durability and thickness.

It’s waterproof: While modified bitumen roofs do rely on seams, unlike ballasted built-up roofs, these seams are welded together, preventing leakage.

It’s unlikely to break: Due to its high tensile strength, a bitumen roof is unlikely to develop any major cracks.

It can handle the cold: Modified bitumen is highly resistant to cold temperatures. The material remains flexible even when temperatures go below -7 degrees Fahrenheit, making it very unlikely to crack or break.

Why do some consider it not to be the best of all flat roofing solutions?

It doesn’t offer much protection: Compared to a built-up roof, a bitumen roof doesn’t offer as much protection against falling branches or hailstorms.

It doesn’t last as long: Compared to other flat roofing options, a bitumen roof lasts about 5-10 years before it must be replaced or repaired.

It’s not so safe to install: When bitumen is heated, it releases a number of harmful fumes and a foul odor that could last a few days.

It isn’t water resistant. Without a proper flat roof gutter system, a bitumen roof can collect puddles of water, which could damage its surface and reduce its lifespan further.

AMECOs Roofing Solutions

By this point, you should have a better idea of the most popular roofing systems for flat roofs and which suits your needs best.

What’s clear is that there is no best flat roof system that fits all needs and purposes, and each system comes with its own pros and cons. So, whether it’s regular maintenance and repairs that you’re looking for, or a complete flat roof replacement, partnering with a reliable roofing supply company is crucial.

The expert team at AMECO Solar and Roofing provides all kinds of roofing solutions, from finding the right materials or identifying a faulty installation. For answers to more detailed questions such as “What roof system is best for multiple level flat roof?” or considering your options when it comes to the best residential flat roof system or traditional vs. solar roofing, the team is ready and willing to give you the shelter you deserve.