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A Quick Guide To Commercial Flat Roofing Systems

Posted on May 28, 2024

commercial flat roofing

Are you in the process of installing a new commercial roof or replacing your existing system? If so, you are in the right place. A commercial roof is one of the most critical components of a building, as it protects the employees and products from the elements and helps regulate internal temperatures and energy costs. 

Making the right decision on which roofing system to install is crucial, as it can impact everything from upfront costs and long-term maintenance requirements to energy efficiency and the overall lifespan of the roof itself.

As a building manager or owner, your time is precious, and you likely don’t have the luxury of extensively researching every available roofing option. That’s where this quick guide comes in. We understand that you need concise, accurate information to help you make an informed decision. 

In the following paragraphs, you will get an overview of some of the top commercial flat roofing systems, their costs, lifespan, and other factors you need to know. 

Parts Of A Commercial Roof: What Makes A Commercial Roofing System? 

Like a residential pitched roof, flat roofs are also made of different layers. Each layer or part of the commercial flat roof plays an important role in its overall functioning, so it’s important to not compromise any of them. Here are the parts that your contractor will install: 

  • Roof Deck: The base layer that provides structural support for the entire roofing system. It can be made of materials like concrete, metal, or wood.
  • Insulation: The roofing insulation helps regulate the building’s temperature and improve energy efficiency. Common insulation materials include rigid foam boards and spray foam.
  • Vapor Barrier: A moisture-resistant layer that prevents condensation buildup, which can lead to rot and other issues.
  • Roofing Material: The primary waterproofing layer that protects the building from rain, snow, and other environmental factors. Options include single-ply membranes, built-up roofs (BUR), or modified bitumen.
  • Flashing: Metal or synthetic strips used to seal roof edges, penetrations (e.g., vents, pipes), and transitions to prevent water infiltration.
  • Ballast or Protective Layer: For some roofing systems, a layer of gravel, pavers, or other materials is added to protect the membrane from UV radiation and physical damage.

Types Of Roofing Materials

As mentioned above, the roofing material is the outermost layer of your commercial flat roof, and also the layer that faces the wrath of the Wisconsin weather. You have several options when it comes to choosing a commercial roofing membrane. Here are some of the top options: 

Single-Ply Membrane 

Single-Ply Membrane

A single-ply membrane is a popular choice for commercial flat roofs due to its ease of installation and cost-effectiveness. This roofing system consists of a single layer of synthetic material, such as thermoplastic polyolefin (TPO), polyvinyl chloride (PVC), or ethylene propylene diene monomer (EPDM) rubber.

If you have your heart set on installing a single-ply roofing membrane and want to know about them, check out the following blog posts: 

Built-Up Roof (BUR)

Built-Up Roof

A built-up roof, or BUR, is one of the most common and time-tested flat roofing systems used in commercial applications. It consists of multiple layers of reinforced fabrics and bitumen (a sticky, semi-solid form of petroleum), which are alternated and then surfaced with a layer of gravel or a mineral cap sheet.

Modified Bitumen 

Modified Bitumen 

Modified bitumen is a popular alternative to traditional built-up roofing systems. It consists of a base sheet or mat that is reinforced with polyester or fiberglass and then coated with a modified bitumen compound. This compound is a combination of asphalt and various modifying agents, such as rubber or plastic, which enhances the roofing system’s flexibility and durability.

Green Roofing Systems

Green Roofing Systems

While not technically a roofing material, green roofs or vegetative roof systems, also known as living roofs, are an environmentally friendly option for commercial flat roofs. These systems involve the installation of a waterproofing membrane, followed by a growing medium and various types of vegetation, such as grasses, wildflowers, or even small shrubs.

How Much Does A Commercial Flat Roof Replacement Cost?

As a building owner or manager, the first thing you think about before you replace your roof is the cost per square foot. To save you time, we have compiled the cost of common flat commercial roof materials below. 

Roofing MaterialCost per Square Foot
Thermoplastic Polyolefin (TPO)$4 – $14
Ethylene Propylene Diene Monomer (EPDM)$4 – $12
Polyvinyl Chloride (PVC) $4 – $12
Built-Up Roof (BUR)$5 – $8
Modified Bitumen$4 – $8
Green Roof$10 – $25

To learn more about these costs, read our blog post: How Much Does Flat Roof Replacement Cost In Wisconsin (2024)

The Installation Process Of Commercial Flat Roofs

Regardless of the flat roofing system you choose, the installation process is crucial to ensure the longevity and performance of your roof. Here’s what you can expect during the installation:

  1. Preparation Of The Surface: The existing roof will be inspected, and any necessary repairs or replacements will be made to the deck.
  2. Installing The Insulation: Depending on the roofing system and your building’s energy efficiency requirements, insulation may be installed before the roofing membrane.
  3. Membrane Installation: The roofing membrane or layers of the chosen system will be carefully installed according to the manufacturer’s specifications and industry best practices.
  4. Sealing With Roof Flashing: Flashing will be installed around roof penetrations, such as vents, pipes, and skylights, to ensure a watertight seal.
  5. Final Roof Inspection: A thorough inspection will be conducted to ensure the roofing system has been installed correctly and is functioning as intended.

Key Considerations for Selecting a Commercial Roof

Choosing the right commercial roof largely depends on two critical factors: the structure of your building and the climate you’re operating in. Although both aspects demand thorough evaluation, with understanding, you can navigate this selection process smoothly.

Evaluate the Building Structure and Roof Shape

The physical characteristics of a building play a significant role in determining which type of commercial roof is right. It’s integral to consider not only the size of your flat roof but also its design when selecting roofing materials.

Additionally, surveying load-bearing capacity is crucial before picking heavy materials. Professional consultants can conduct structure evaluations to ensure the new roof will be properly supported. 

Climatic Conditions Of The Area

Local weather conditions impact how long your commercial roof lasts—not all types of commercial flat roofs perform effectively under all climatic conditions. For hot regions prone to intense sunlight exposure, reflective materials like TPO or PVC offer better energy efficiency by resisting UV rays while maintaining cooler interiors. 

Conversely, businesses located in storm-prone areas should choose options offering superior wind or hail resistance.  Similarly, for colder states such as Wisconsin, which receives heavy snowfall, the threat of pooling water is lessened by utilizing steeply pitched styles, which promote faster snow shedding.

Apart from these two factors you should also look at the following: 

  • Your energy requirements
  • Cost of the roofing membrane
  • Personal preferences

Trust Our Reputed Experts For Your Commercial Flat Roof Replacement

A commercial roof replacement can be tough and complicated, but it doesn’t have to be. Our roofing experts at Prestige Roofing are here to help you navigate the process. 

We have years of experience in commercial roof replacements and have handled all the popular roofing materials. Whether you want to install a TPO or EPDM flat roof, contact us today at (920) 791-0414 for a free project consultation.