Have you wondered about the different types of roofs you see in buildings in the U.S.? 

Most houses in the U.S. have pitched (sloped) roofs, and a few have flat roofs. Why do some people choose to use a flat roof system? What is the difference? Find out all about it by reading our piece about flat roofs below. 


What is a Flat Roof? 

Despite its name, a flat roof isn’t flat. While it may appear level to the naked eye, a flat roof has a slope, or as we call it, a pitch, between 1 – 10 degrees. Some people call it a “low slope” roof for this reason.  

Why are they not completely flat? The answer lies in proper drainage. Water would accumulate without a slope, leading to leaks and water damage inside the building. Therefore, flat roofs have a slight incline to ensure drainage and prevent cracks. However, due to their low pitch, flat roofs are more susceptible to water pools and, therefore, water damage. As a result, flat roofs have different systems consisting of various elements and designs to help give extra protection. 

The different types of roofs

There are three common types of flat roofs you see in the U.S.:

  • Built-Up Roof (BUR)

Contains multiple layers of hot gravel and tar to help seal and protect the roof. However, BUR is heavy and requires a strong roofing structure. Nevertheless, it’s the most cost-effective and reliable option. 

  • Modified Bitumen Roof

Consists of overlapping layers of single or double-ply asphalt sheets. Unlike BUR, a modified bitumen roof uses no tar (which can smell) and is typically top-coated to seal cracks.   

  • Single-Ply Membrane Roof

Uses a single waterproof sheet made from synthetic materials to give extra protection from water. This type of layer is a DIY project but costs the most compared to other options. 


How are flat roofs Different from Sloped Roofs?

There are several key differences between a sloped roof system and a flat roof:

A flat rooftop bar


Flat roofs have a pitch of 1 – 10 degrees, while sloped roofs have an angle of over 10 degrees. 


Drainage system

Due to its low-pitched characteristics, flat roofs require different designs and drainage to prevent water from accumulating and causing damage. In contrast, sloped roofs rely on gravity to drain water and other debris, which reduces the risk of damage.



Generally, sloped roofs require less maintenance because they have a natural drainage system. With extra elements and design, flat roofs need to be inspected and maintained regularly to ensure effective function.  


Cost to build

Overall, a flat roof is more economical than a sloped roof, as it requires fewer materials and manpower to construct.



Flat roofs offer more usable space. The flat top can be used for various things, such as rooftop outdoor living areas or solar panels. On the other hand, pitched roofs allow for an attic, therefore, more storage. 



Flat roofs are often associated with modern architecture and have become increasingly popular. However, style is a matter of personal preference, so it’s up to you which design you like best for your home. 


How do Flat Roofs Drain Properly? 

Different guttering and roof drainage systems

Proper drainage is crucial for any roofing system, especially for flat roofs due to their low pitch. Here are the three common drainage systems used in flat roofs:

Interior Drains

These are similar to drains in your showers, designed to collect water and lead it into pipes that travel down to the gutter or downspout. Drains are a popular choice because they can’t be seen and are effective in collecting water. 



The most commonly used in homes and the most cost-effective options. Roof gutters catch water and divert it into a downspout, then down to the ground.



Arguably the most effective type of drainage system for flat roofs. Scuppers are openings made along the low points of the roof. They are usually connected to the downspouts, bringing water to the ground. They can drain quickly and prevent water from pooling on the roof. 


What is Flat Roof Maintenance?

Maintaining flat roofFlat roofs require regular maintenance to ensure they remain in good condition and free from leaks and other damages. Flat roof maintenance tasks include: 

  • It is important to perform regular inspections to catch any potential hazards early. A roofing professional can inspect the roof for signs of wear and assess the condition of the drainage system.
  • Checking the drainage system to make sure proper water flow is maintained. Flat roofs heavily rely on effective drainage to prevent water pooling and damage. 
  • Cleaning any debris from the roof that can hinder the function of the drainage system. Debris can accumulate over time and cause clogging.  
  • Clearing potential hazards, such as trimming nearby trees to prevent damage to the roof and ensure leaves don’t fall into the roof and clog the drainage system.  



Flat roofs are gaining in popularity for many reasons. They’re cheaper to build, provide a fresh and modern look, and offer more usable space for homeowners to create various areas, such as rooftop outdoor living rooms. Flat roofs require attentive and regular maintenance because their low-sloped characteristics make them more susceptible to water pooling and damage. Moreover, an effective drainage system, such as interior drains, gutters, and scuppers, is vital in preventing damage. 

Last but not least, opting for a reputable roofing contractor who can help you properly maintain your flat roof system and provide the best advice is essential. At JP Roofing, we specialize in all types of roofing, including flat roofs. We are committed to providing our customers with high-quality workmanship and excellent customer service. Contact us today for any roofing assistance you need!

Contact JP Roofing Today!