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How Much Does It Cost To Install A Flat Roof?

Typical Range: $2,828 - $8,095

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On This Page:

  1. The 3 Types of Flat Roofs
  2. Pros & Cons of Flat Roofing
  3. Flat Roof Repairs

Adding a distinctly modern, urban look to a building, flat roofs have gained popularity over the years because they are actually easier to install and maintain than traditional pitched roofs are. While they are not exactly flat in a technical sense—flat roofs usually have a 1/8-inch pitch to help drain water—homeowners can use these roofs as deck areas when the spaces are properly sealed and maintained. Whether you already have a roof that needs a replacement or are contemplating this type of roof on a remodel or new build, it is important to understand the different options and price points available for this modern roofing style.

On average, a flat roof costs about $250-$350 per square, which is a measurement that equals 100 square feet, to install. Similarly priced and much easier to assess than typical sloped asphalt-shingle roofs, flat roofing offers different advantages and features that are important to review before making a decision.

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National Average
Typical Range
$2,828 - $8,095
Low End - High End
$1,200 - $14,445

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Cost data is based on actual project costs as reported by 977 HomeAdvisor members in .

The Three Types of Flat Roofs

At the heart of any flat roof installation is deciding on the type of roof that best fits your home style, intended use, climate, and budget. The three main types of materials and methods used in installing flat roofs offer homeowners a variety of benefits and disadvantages.

Built-up Roof

The most traditional method, the built-up roof consists of several layers of materials that are laid down atop each other, including hot tar (bitumen), gravel, fiberglass, and roofing felt. This type of roof is fire-resistant thanks to the layers of gravel and can last up to 30 years. However, because of the hot tar, the installation of this type of flat roof should always be done by a professional roofer. It is also a very smelly process and is not recommended for occupied homes. The average cost of a built-up roof installation is $3.50-$7 per square foot.

Modified Bitumen

In direct contrast to the layered approach of the built-up roof, the modified bitumen system utilizes only one layer of rolled material, which can be made of various compounds and installed one of two ways.

The traditional installation, known as torch-down application, requires installers to heat the materials on the roll as they lay them down on the roof. A layer of felt is applied to the roof, followed by a primer and the strips of bitumen, which are sealed onto the roof via the flame of a large torch.

Because this is highly specialized and presents a fire hazard, torch-down modified bitumen roofs are rarely used outside of the professional realm. By contrast, the more modern modified bitumen approach, called peel and stick, is a possible DIY project. Both types of modified bitumen roofing systems are notable for their light colors that reflect heat, their up-to-30-year lifespan, and their middle-grade price. In fact, the installation of a modified bitumen roof generally costs between $3-$6 per square foot.

Rubber Membrane

Made of "true rubber" or ethylene propylene diene monomer (EPDM), the rubber membrane roof is literally like a flattened car tire. However, the chemistry of the material is such that this type of roof actually resists sun damage. It is also lightweight, resistant to scuff marks and tears, and relatively easy to patch in the event of a leak. EPDM roofing is available in two colors—black and white—which serve the needs of different climates and budgets. While the black variety absorbs quite a bit of heat, the white material costs 30 percent more on average because of its heat-reflecting properties. While the average cost to install EPDM roofing is between $4-$6 per square foot, it is easy to install EPDM roofs yourself because there are several systems that you can use to secure them according to your skill level and comfort. This includes mechanical anchoring with fasteners or adhesive anchors or ballasting the material with stone.

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Pros & Cons of Flat Roofing

In addition to their aesthetic appeal and relationship to modern architecture and building methods, flat roofs have gained substantially in popularity over the past few years because Energy Star has actually rated them more efficient than a traditional pitched roof. In addition, the minor slope of a flat roof, when properly treated and sealed, is completely safe to walk on. With a little design savvy, it is easy to turn a flat roof on a garage, for example, into a unique outdoor space for your home.

Flat roofs do come with their downsides, however. For starters, they tend not to last as long as a pitched roof can. The average asphalt shingle roof, for example, has a lifetime of 20-30 years. Flat roofs, on the other hand usually need replacement every 15 years. In addition, some types of roofing and climatic conditions require homeowners to replace their roofs as often as every 10 years. Homeowners in colder climates with heavy snowfall should also think twice about installing a flat roof on their home or addition. This is because the low-grade slope may slow drainage, leading to pools of water and ice dams during the winter months.

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Flat Roof Repairs

Understanding the common issues and promptly repairing them is the best way to maximize the life of your home's flat roof. The most common repairs include fixing leaks, resealing surfaces, and replacing and maintaining gutters to ensure proper drainage. Look for water pooling or puddling in spots on the roof; these are areas that are likely to begin leaking, and repairing them before they evolve into full-on leaks can save money and headache.

In addition, it is important to regularly inspect your roof and promptly address any tears, holes, or leaks you find. This is easy to do on flat roofs because they are more stable to walk on than pitched roofs. Small leaks can typically be patched if they are noticed early enough, which is why inspection is critical. Hiring a roofer to patch a leak costs $300-$500 on average. Promptly addressing these issues through DIY repair or contacting a roofing professional is the best way to save money over a full flat roof replacement.

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Like any part of your home, properly maintaining your flat roof is the best way to prevent damage and extend its life, ultimately saving money. One way to do this is to carefully consider the initial investment into your roof. Adding layers on a built-up roof, for example, increases durability and longevity. Likewise, adding underlayment, which is a waterproof layer on top of the plywood, before laying roofing material helps to prevent leaks. Regularly sealing your roof is another way to prevent leaks, as is proper winter care and maintenance. After 48 hours, a small ice dam on a flat roof can begin to spring leaks underneath.

Common maintenance tasks that are easy to perform but critical for the upkeep of a flat roof include clearing the gutters after storms or at least every six months. Homes with many pine trees nearby may need their gutters cleaned every four months. In addition, it’s important to sweep off the roof periodically. Flat roofs are much more likely to collect leaves, dirt, and other debris that can accumulate in piles and trap standing water, resulting in leaks. Finally, be sure to inspect the flashing around chimneys and other roof joints for cracking, and apply caulk to the cracks or replace pieces of the flashing if necessary to prevent leaks.

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