Modified bitumen roofing systems have gained popularity due to their durability and weather resistance. This article will explore the cost of a modified bitumen roof and the factors that influence its pricing.

A Brief Introduction to Modified Bitumen Roofing Systems

Modified bitumen roofs are flat roofs commonly used in commercial and residential buildings. They are made from asphalt-based materials, reinforced with polyester or fiberglass, and modified with rubber or plastic polymers. This combination creates a durable, flexible, and long-lasting roofing material that can withstand harsh weather conditions.

Modified Bitumen is among the most popular flat roof materials, especially for commercial buildings. This is why most commercial flat roofs have them.

How Much Does a Modified Bitumen Roof Cost?

How Much Does a Modified Bitumen Roof Cost?

Several factors come into play when it comes to the cost of a modified bitumen roof. Let’s compare the average costs of low-end, average, and high-end installations to provide a general overview.

Average Cost Comparison:

  • Low end: $4,900
  • Average: $9,750
  • High end: $14,600

The national average cost for a modified bitumen roof installation is approximately $6,920. The typical range for modified bitumen roof installations is between $3,221 and $10,647. This range accounts for variations in labor costs, material prices, and the specific requirements of each project.

Regarding the low and high end of the cost spectrum, a modified bitumen roof can range anywhere from $1,200 to $22,000. The low end represents simpler installations with smaller roofs, while the high end includes larger, more complex projects that may require additional features or customization.

These estimates provide a general overview of the cost range for a modified bitumen roof installation. However, consulting with a professional roofing contractor is important to get an accurate estimate based on your specific needs and location. Factors such as the condition of the existing roof, any necessary repairs or modifications, and the desired features will all contribute to the final cost.

Cost of Modified Bitumen Roofing per Square Foot

Let’s examine the expenses per square foot to better understand the cost breakdown. The table below illustrates the various factors that contribute to the overall cost:

Removing the old roof:

  • $1.00 – $2.50

Materials and supplies:

  • $0.70 – $2.20

Installation labor:

  • $2.30 – $5.00

The total flat roof replacement cost will depend on many other factors. It’s crucial to note them for every DIY flat roof replacement project.

Factors That Affect the Cost of a Modified Bitumen Roof

Several factors influence the cost of a modified bitumen roof. Let’s take a closer look at each of these factors:


Skilled labor costs vary from region to region, and hiring an insured roofing contractor will affect the overall cost. Luckily flat roof installation is not always too complex, which makes it more affordable than pitched roofs.


Additional roofing layers, such as insulation or protective coatings, can add to the flat roof cost.

Roof Size

The size of the roof plays a significant role in determining the cost. Larger roofs require more materials and labor. This is always a crucial consideration when calculating flat roof costs.

Slope and Pitch

Flat roofs with a slight pitch are generally easier to install and may cost less than roofs with steeper slopes.


Complex roof designs, multiple roof angles, or architectural features can increase installation costs.

Removing the Old Roof

This process will add to the total cost if an existing roof needs to be removed before installing the modified bitumen roof.

Roof Repair Costs

Any necessary repairs, such as fixing leaks or structural issues, will impact the final cost.

Installing Vents

Proper ventilation is crucial for a healthy roofing system. Adding vents to the roof can increase the installation cost.


Depending on local regulations, obtaining permits for the installation may add to the overall expenses.

Underlayment and Overlayment

The type and quality of underlayment and overlaying materials can affect the cost.

Material Prices

The prices of modified bitumen roofing materials can vary depending on the specific type. Here are some examples:

Prices per Roll:

  • Low end: $150
  • Average: $350
  • High end: $560

Price of Modified Bitumen Roofs per Polymer:

  • APP (Atactic Polypropylene): $3 – $5 per square foot
  • SBS (Styrene Butadiene Styrene): $4 – $6 per square foot

Final Thought

When considering the cost of a modified bitumen roof, it’s crucial to take into account the factors discussed above. While the initial investment may be higher than traditional pitched roofs or asphalt shingles, modified bitumen roofing offers numerous benefits. These include durability, energy efficiency, and better resistance to extreme weather conditions.

Consulting with a professional roofing contractor and obtaining an accurate estimate will help you determine the best solution for your roofing needs.

San Diego County Roofing & Solar offers the best flat roofing solutions. They have many years of working with modified bitumen roofing materials for commercial properties. Get in touch with this team if you want a reliable roof.


How long does a modified bitumen roof typically last?

Modified bitumen roofs are known for their durability and longevity. A well-installed and properly maintained modified bitumen roof can last between 20 to 30 years. However, factors such as climate, maintenance practices, and the quality of installation can impact the roof’s lifespan.

Can I install a modified bitumen roof myself?

Installing a modified bitumen roof requires specialized knowledge and skills. Hiring a professional and insured roofing contractor with experience in working with modified bitumen roofing systems is recommended. DIY installation can lead to costly mistakes and may void any warranties associated with the roofing materials.

Are modified bitumen roofs suitable for residential properties?

Yes, modified bitumen roofs are suitable for both residential and commercial properties. They provide excellent protection against the elements and are especially beneficial for flat or low-slope roofs commonly found in residential buildings.

Can a modified bitumen roof be installed over an existing roof?

In many cases, modified bitumen roofs can be installed over an existing roof, which can help reduce installation costs. However, it’s crucial to assess the existing roof’s condition and consult with a professional roofing contractor to determine if this approach suits your specific situation.

Are modified bitumen roofs more expensive than traditional roofing materials?

Modified bitumen roofs may have a higher initial cost compared to traditional roofing materials such as asphalt shingles. However, they offer superior durability and weather resistance, which can result in long-term cost savings. Additionally, the energy efficiency and potential for better insulation can contribute to reduced heating and cooling costs over time.