Conventional Vs. Inverted Roofing: Which Roof System is Right for You?

When adding a new roof to your commercial building, it pays to do your homework in advance. Asking the right questions now can help you to determine the best fit and way to move forward with confidence. For instance, is there a significant difference between conventional and inverted roofing? Which method is faster? Cheaper? More durable? A closer examination of the pros and cons of conventional vs. inverted roof assembly reveals the answers to these and other pressing questions. But first, let’s establish a working definition for each system.

What Is a Conventional Roofing System?

In a “conventional” roofing system, insulation is located directly beneath the roof membrane. This long-standing practice exposes the roof to environmental elements such as shifting air temperature and natural disasters. However, the insulation itself is protected from exterior conditions. According to experts, a conventional roofing system is the most common low-slope application.

What Is an Inverted Roofing System?

Often referred to by the colloquial term “inverted” or “upside-down” roof, Insulated Roof Membrane Assembly (IRMA) was patented in 1968. Since that time, the inverted roofing system has become better known as Protected Membrane Roof Assembly (PMRA) or Modified Protected Membrane Roof Assembly (MPMRA). Unlike a conventional roofing system where insulation is located below the roof membrane, an inverted roof has the opposite configuration. In other words, insulation is placed over top of the membrane in PMRAs and MPMRAs. While there are differing applications of this method available to consumers, the basic premise remains the same – inverted roofing systems provide reliable protection from the elements through insulated roof assembly.

Pros and Cons of a Conventional Vs. Inverted

Roofing System When it comes to choosing between a conventional vs. inverted roofing system, there are several factors to explore, depending on your individual needs. Have a look at some of the top advantages and disadvantages to gain a broader perspective on each roofing system.

Advantages of a conventional roofing system include:

  • High load bearing capacity (resulting in lower structural costs)
  • Reduced cost of materials and installation
  • Less risk of pooling water or other water drainage issues when enhanced with proper materials (thereby preventing algae or vegetation issues)
  • Durable protection from acrid manufacturing conditions
  • Simple, timely installation process

Disadvantages of a conventional roof system include:

  • Shorter life span (typically lasts for 25-30 years)
  • Higher cost of maintenance
  • Climate exposure (resulting in issues such as thermal cycling and ultraviolet degradation)
  • Greater likelihood of splitting, ridging, and blistering
  • Less eco-friendly

Advantages of an inverted roofing system include:

  • Longevity (lasts up to 40 years)
  • Lower maintenance costs
  • Ongoing protection from hazardous environmental conditions
  • High compression strength
  • More eco-friendly

Disadvantages of an inverted roofing system include:

  • Higher cost of installation and structural requirements
  • Somewhat longer and more complex installation process
  • Build-up of dirt (leading to vegetation)
  • Difficulty in pinpointing water leaks
  • Lower heat retention (without extra insulation)

Conventional vs. Inverted Roofing System

Clearly, the decision to install a new roof on your commercial property warrants careful consideration. The main distinction between a conventional vs. inverted roofing system is the placement of insulation. And yet, that placement can make all the difference to the cost, installation, structure, durability, and longevity of a roof membrane. As demonstrated, both conventional and inverted roofing systems have certain perks to offer and pitfalls to avoid. So, where does this leave a commercial property owner?

Prioritizing your needs and goals before making an investment will pay dividends. In fact, you may even want to create a list of your own to compare with the top pros and cons of conventional vs. inverted roofing. Take, for example, the cost of a new roof. Are you looking to save money upfront or over the long run? If your current budget is tight, then the installation of a conventional roof system might be the way to go. On the other hand, if you do have the financial means to pay for an inverted roof, you might opt for this system to save money in maintenance fees down the line. The same advice can be applied to other components such as low heat retention, e.g., those who live in a temperate climate may not have to worry about cold winter temperatures and therefore decide to select an inverted roof over a conventional one. Whatever your situation, the right roofing system can enhance your commercial property. Dig deep to choose the best system and application for your site-specific needs. Additionally, it never hurts to consult a professional for a second opinion. An expert in building condition assessments can evaluate your specific building and make recommendations to help you make the most of your investment and overall site goals. With over 30 years of experience in the industry, AEL Environment is well-equipped with the skills and knowledge necessary to conduct thorough assessments, taking into account factors such as environmental impact, regulatory compliance, site suitability, and any other relevant considerations.

Email Daniel Staring, our Building Coordinator at: and let him know your goals for your commercial property. He would be more than happy to help.

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