Flat roofs are popular for many commercial buildings due to their practicality and cost-affordability. However, it’s essential to understand the costs of new flat roof installations, especially when considering a replacement or new construction project.

This article aims to provide a comprehensive overview of how much a flat roof installation can cost, including factors that influence the cost, the installation process, and the best flat rooftop materials to use.

Choosing a professional contractor experienced in flat roof installations is crucial to ensure the job is done correctly and within budget.

With this information, you’ll be better equipped to decide when to replace your old roof.

roof repair or replacementHow to Install a Flat Roof?

Flat roof installations require a different approach than traditional sloped rooftops. The specific steps may vary depending on the material used, but the basic process is as follows:

how to choose best type of roofing material#1 Preparation of the Roof Deck

The installation process starts with preparing the surface of the rooftop. Firstly, the old roof is stripped, and any damaged sections are repaired to ensure a smooth surface for the new roof.

#2 Installation of Underlayment

roof repair or replacementOnce the surface is prepared, the flat roofing installation process continues with underlayment laying. Underlayment is a waterproof layer that protects the rooftop from leaks and provides a barrier against moisture and heat.

Different types of underlayment are available, including asphalt-saturated felt and synthetic underlayment. The choice of underlayment material depends on the roofing material used.

#3 Application of Flat Roofing Materials

house with steel roofingThe next step is to apply the roofing materials. This is typically done by laying down sheets of material and securing them to the roof deck. The flat roof material is then sealed to prevent water infiltration.

Flat roof materials come in various forms, including rolled roofing, membranes, and built-up roofing.

Rolled roofing is typically made of asphalt and is suitable for smaller flat roofs. On the other hand, membranes are rubber or plastic sheets applied in sections.

Furthermore, built-up roofing comprises several layers of asphalt and roofing felt and is typically used on large buildings.

#4 Finishing Touches

Roof Repair or Replacement - Consider This Before Hiring a Roofing CompanyFinally, any necessary finishing touches are made, such as installing flashing around edges and penetrations.

Choosing a professional roofing contractor experienced in flat rooftop installations is essential. A contractor’s services include recommending the best roofing material and installation process for many projects, considering cost, quality, durability, and climate conditions.

Moreover, the choice of roof material and the installation process will depend on the size of the rooftop, the climate conditions, and the property’s specific requirements.

Do You Need Underlayment for Flat Roofs?

house with brown shingle roofUnderlayment is a layer of material installed between the roof deck and the roof material. It is a barrier to prevent water infiltration and protect the roof deck from damage.

This is important for flat roofs because it provides extra protection against water infiltration. Flat roofs are more prone to water infiltration than sloped roofs, so the underlayment helps to prevent water damage to the building.

Several types of underlayment can be used on new flat roofs, including asphalt-saturated felt, rubberized asphalt, and synthetic underlayment.

The type of underlayment used depends on several factors, including the climate, the roofing material, and the budget.

Choosing the proper underlayment for your new flat roof ensures longevity and effectiveness. It must be compatible with the roof’s material and have appropriate waterproofing and durability for the specific climate.

Furthermore, the underlayment cost will depend on several factors, including the type of underlayment used, the size of the rooftop, and the labor cost. The underlayment cost for flat roofing ranges from $0.25 to $1 per square foot.

Additionally, underlayment is an essential component of flat roof installation. It provides an extra layer of protection against water infiltration and helps ensure the roof’s longevity and effectiveness. Choosing the proper underlayment is essential for ensuring the best performance of your flat rooftop.

roofing contractors installing synthetic underlaymentWhat Is the Best Material to Put on a Flat Roof? 

You can use various materials, such as thermoplastic polyolefin, to cover a flat rooftop, each with unique properties and benefits. Some of the most popular flat roofing materials include:

roofing specialist inspecting a residential roofAsphalt Rolled Roofing

Asphalt rolled roofing is affordable and suitable for small flat roofs. It’s made of asphalt and comes in large rolls, making it easy to install.

water damage and roofing of austin synthetic underlaymentBuilt-up Roofing (BUR)

A built-up roof is a traditional roofing material type made up of several layers of asphalt and roofing felt. It is suitable for large commercial buildings and is known for its durability and long life span.

roofers repairing a roofSingle-ply Membranes

This roofing material is rubber or plastic and comes in large sheets. It’s highly resistant to UV rays and cost-effective for flat roofs.

Roof Repair or Replacement - Consider This Before Hiring a Roofing CompanyGlass Reinforced Polyester (GRP)

GRP is a lightweight roofing material made of fiberglass reinforced with resin. It’s very resistant to UV rays and is a popular option for commercial buildings.

Ethylene Propylene Diene Monomer (EPDM)

house with brown shingle roofEthylene Propylene Diene Monomer (EPDM) is a popular flat roofing material. This synthetic rubber material is very resistant to UV rays, which makes it an excellent choice for flat roofs in sunny climates.

It is also very durable and can last up to 50 years with proper maintenance. EPDM is a cost-effective solution for flat roofing and is suitable for residential and commercial properties.

The best flat roof material will depend on the property’s specific requirements and the area’s climate conditions.

Furthermore, one of the traditional roofing materials used on flat roofing is hot tar.

Hot tar is a cost-effective material used for many years on flat roofs. However, it requires high expertise to install, and it is not the most durable material available.

Despite this, hot tar is still used on many projects, mainly commercial buildings.

What Is the Flat Roof Replacement Cost?

two story residential houseThe new flat roof replacement fee will depend on several factors, including the roof size, the material used, and the location of the building.

Here are some factors that affect flat roofing replacement costs:

Flat Roof Installation Cost per Square Foot

To convert a flat roof, the cost per square foot can range from $3 to $20. This cost will depend on the material used, the project’s complexity, and the building’s location.

Cost of Hiring a Flat Roofing Installation Contractor 

Hiring a flat roofing installation contractor or company will also impact the overall cost of converting the roof. The contractor or flat roof installation company will typically provide a quote based on the size of the roof and the material used.


Converting a flat roof can be cost-effective for many commercial property owners. A flat roof can improve the energy efficiency of a building and can also increase the value of the property.

When budgeting for a flat roof conversion, consider the following factors:

  • The cost of the material
  • The cost of the contractor or company
  • Any necessary permits or fees

Working with a flat roof installation contractor or company is essential to determine the project’s overall cost.

Key Takeaway

roofing experts on residential roofThe flat roof is a popular choice for many commercial buildings and can provide a cost-effective solution for those looking to replace or install a new roof.

Understanding the installation process, the importance of underlayment, the best materials, and the cost of converting a flat roof can help property owners make informed decisions regarding their roofing needs.

Hiring a reputable and experienced flat roof installation contractor or company is crucial to ensuring a successful roofing project.

These professionals will have the expertise to help property owners choose the best materials for their needs, such as thermoplastic polyolefin, provide accurate quotes, and ensure that the installation is performed correctly.

Whether you want to replace an old roof or install a new one, a flat roof is a cheap and durable option for commercial property owners. Considering all of the factors outlined in this article, you can make an informed decision and ensure your roofing project succeeds.