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Everything You Need to Know About Flat Roofs: Types, Cost, & More

Contractor installing a flat roof

Flat roofs require special materials and care. They differ from their sloped counterparts in more than just appearances. Materials, benefits, and costs are all distinct when it comes to flat roofing. If you’re a commercial building owner, you’ll likely have to deal with flat roofs first hand. If you’re unfamiliar with their specialized nature, it can be difficult to understand what you’re getting into. 

Here at 970 Services, our team of licensed roofing contractors are schooled in all aspects of commercial roofing. We know our way around a roof, sloped or otherwise. Read on to learn everything you need to know about flat roofs. 

Types of Flat Roofs

As simplistic as a flat roof may seem, there are actually quite a few variations in how they’re built. Knowing the difference between various types of flat roofs can help you better understand how to maintain your roof. 

Here are the different types of flat roofing materials:

Thermoplastic Membrane Flat Roof (PVC or TPO)

Thermoplastic Membrane Flat Roof

This type of roofing is a single-ply layer of material fixed to the roof with screws and plates. Typically, it will be white or gray but it can also come in other colors. They’re praised for their high-temperature tolerance and durability. There are two types of thermoplastic membrane roofing: polyvinyl chloride (PVC) or thermoplastic olefin (TPO).

PVC is the third most-produced synthetic plastic polymer. As far as roofing goes, it’s relatively easy to install due to its flexibility. It’s also the sturdiest of the two thermoplastic membrane roofing variations. They can usually last up to 20 years.

TPO is considered a more eco-friendly variation of the thermoplastic membrane roof. Once it comes time to replace the sheeting, you can recycle the old material. Some perks of this roofing material include UV absorption and flame resistance. TPO roofing can last anywhere from 15 – 20 years. 

Overall, thermoplastic membrane roofs remain a popular option due to their relatively low cost, energy efficiency, and durability. 

Build Up Roofs (BUR)

Built up roof

Build up roofs have been a mainstay in flat roofing for around 100 years. With their textured tar and gravel exterior, they’re fairly easy to identify. The installer will build it up -hence the name- until there’s a dense layer of minerals and tar packed on the rooftop. 

This is a popular option due to its low maintenance needs and reasonable cost. It also does a great job combating UV rays. When maintained properly, they can last up to 15 – 20 years. But there are a couple of downsides. It doesn’t hold well against adverse weather conditions and once a leak does occur, it can be difficult to find the source. It’s also quite heavy and not very energy efficient.

If you live in a state like Colorado, we don’t recommend you install this roof type.

Rubber Membrane Flat Roof (EPDM)

Rubber membrane flat roof

This roofing material is a single-ply membrane consisting of rubber. It’s either glued down or anchored with fasteners or rocks. If rocks are used to secure the rubber, it will have a similar look to a build up roof. But instead of gravel, the membrane will be held down by much larger stones. 

EPDM roofing can come in black or white. It’s considered the cheapest of all the roofing options to install as well as to repair. Installation is typically a quick and easy job. Usually, rubber roofing lasts about 25 to 30 years. If you live in a cold climate, it’s best to go with the white option as the black roofing material can draw in heat and end up costing you in cooling costs. 

Modified Bitumen Flat Roof

Close up of a modified bitumen flat roof

A modified bitumen roof is an asphalt-based sheet similar to the BUR in texture and appearance. It is installed in five layers starting with insulation. Next comes the modified base sheet, modified bitumen membrane, adhesive, and finally, surfacing topcoat. 

The installation of a modified bitumen roof is a long, labor-intensive process. It should be done by a professional every time. The installation process could include hot-mopping, cold-pressing, or self-adhering materials to the roof surface. Though the installation can be arduous, the results are worthwhile. Modified bitumen roofs are very durable, can last up to 20 years, and are easy to repair. 

Spray-On Flat Roof

Spray foam on a flat roof
Photo Credit: Inland Coating

This roofing option is sprayed directly onto the roof just as the name implies. Installation begins with a base layer of high-density polyurethane foam applied with a wand or sprayer. Next, the contractor will spray a layer of waterproof elastomeric topcoat. It will often have a white or gray finish. The entire process lends itself to a quick, seamless installation.

A spray-on roof can be quite costly but for good reason. It can conform to any roof shape easily and offers a near completely waterproof finish as it doesn’t have seams. If properly installed, this roofing can last up to 40 years.

Metal Flat Roof

Metal Flat Roofing

Metal is another popular option for flat roofs. Typically, aluminum is the preferred material due to its malleability. But you can also choose from other metals such as tin, copper, steel, or zinc. Your contractor will adhere large metal sheets to the surface of the roof using screws or other fasteners

This type of roof thrives in dry, warm climates. In these ideal conditions, they can last up to 35 years. The metal sheeting reflects heat and wicks away moderate moisture well. But since there isn’t much drainage on flat roofs, you can run the risk of corrosion issues down the line if you choose metal roofing in a wet climate. 

Green Flat Roof System

Birds eye view of a green roof

Eco-friendly alternatives are all the rage these days – even in the roofing world! Green roofs are made from living plants. This unique, up-in-coming option offers an aesthetically pleasing finish and lower energy bill. They can even absorb air pollutants!

In order to install this type of roof, assure you have a pitch of at least ¼ inch per foot of run and a structurally sound roof. Also note that there must be either a rubber or plastic base material as well as insulation below your green roof. 

Once you’re certain your rooftop can accommodate living plants, you can put the plants in place using planting trays or by creating a “landscape” directly atop the roofing material. Popular plant options include succulents, grassess, and other short vegetation. Also keep in mind seeds from invasive plants might find their way onto your roof so regular weeding is encouraged. 

Concrete Flat Roof

Concrete flat roof

One final flat roof material you can choose from is concrete. Contrary to what you might assume, concrete roofs consist of a few different layers. First, a screed layer is placed down on the concrete slab followed by a vapor barrier. Next comes a layer of insulation covered in a polyethylene film. After all this is applied, only then can a contractor lay down the self-compacting concrete roofing material.

Concrete is a tried and true favorite in flat roofing. They can withstand harsh weather and are fairly easy to maintain. Under ideal conditions, they can last up to 50 years. But due to concrete’s porous nature, this type of roof can experience leaking issues. 

Possible Cost of a Flat Roof 

The cost of a flat roof can vary vastly depending on the size of your building and the type of roofing material you select. Generally, maintenance will range between $200 – $800 in total, however, this can change due to the state where the building resides and the roofing company performing the maintenance.

The lower end of that spectrum will include quick fixes such as unblocking a drain whereas the higher end will include more complex repairs such as stretching, anchoring, and sealing.

Again, we’d like to point out that these are estimates that won’t necessarily reflect the price that your flat roof could cost. There are many details to sort out, so your roof could cost significantly more or less depending on the conditions of the factors layed out in the contract.

Benefits of a Flat Roof

Flat roofing offers a few perks that the commercial building owner could greatly benefit from. 

First off, the cost of flat roofing is significantly more affordable compared to a traditional sloped roof. This is mainly due to the fact that the materials are generally cheaper. There’s also less risk and labor involved in the installation process for the contractor. Additionally, they’re less costly down the line as repair complications don’t tend to crop up as quickly as in a sloped roof.

Another benefit of flat roofing is the potential for added usable space. If you have easy access to the roof, you can turn the space into an outdoor space or lounge. You might consider creating a patio or perhaps even a garden. Multi-family properties are the most common places to get creative with these types of roofs.

Another upside to flat roofing is the quick installation time. There is no need to reschedule your whole life around a roof replacement. Flat roofing usually takes no more than two days. But do keep in mind that this will vary depending on the roofing material you choose and the overall size of the roof.

A final benefit of flat roofing is straightforward, easy maintenance. As we touched on, flat roofs don’t need repairs often. And when they do, it typically won’t be too much of a headache to take care of. Their flat surface lends well to frequent inspections so you can get on top of problems promptly.

Downfalls and Common Problems with Flat Roofing

There are a few downsides to flat roofing too. 

For one, they offer less insulation potential than traditional roofing (pitched/sloped roofs). There isn’t as much room to add in material to shield your building from the elements. This can lead to poor protection from outside temperatures during extreme weather.

Some flat roofs do have a slight pitch – or angle – to account for water drainage. But this isn’t always enough to prevent pooling in the instance of heavy rain or snow. Eventually, this can result in deterioration. This is why periodic inspections are vital. Be sure to regularly clear your draining system to prevent excessive pooling.

Debris pile up is another problem to look out for. Leaves, dust, pine needles, and more can collect on your flat roof. This can lead to blocked drains and, eventually, pooling. 

Over time, your flat roof may crack and warp. This is a problem in and of itself but it can also result in leaks. This is another reason to perform frequent inspections to your flat roof. If you do catch a problem spot, be sure to resolve it as soon as possible.  

To Repair or Replace? 

When built correctly and maintained well, a flat roof can last up to 25 years on average. Of course, this will vary depending on which roofing material you choose. For example, spray-on roofing will typically outlive rubber roofing. When evaluating whether it’s time to repair or replace, take into consideration the age of your roof and how severe the damage is. 

Take a look at the problem areas of your flat roof. Is it an isolated leak or more of a widespread issue? If there’s a minor problem, especially if your roof is newer, it will probably be best to repair it. If your roof is at the end of its lifespan and there are major repairs necessary, it might be more economical to replace the whole roof.

If you’re constructing a new build and are looking for the roof type that will fit your needs and vision, talk with a professional.

For Flat Roofs, Call 970 Services

Our team of roofing specialists is ready and able to help with any problems that may arise with your flat roof or if you need to install a completely new one. We’re here to take the stress out of commercial building upkeep. Whether you encounter a small repair need or decide it’s time to replace the whole roof, we’ve got you covered! 

We proudly serve Northern Colorado, and Cheyenne, WY. Not only can we assist with any roofing need but we also provide fire and water restoration as well as mold removal. Get in touch with us for your free inspection today!

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