Large industrial building with TPO roofing system

TPO roofing systems are an extremely popular choice for commercial and industrial buildings. TPO is a highly durable, UV resistant, and inexpensive single-ply roofing membrane which is best known for its ease of installation and signature bright-white finish.

But as with any type of commercial roofing material, TPO isn’t without its faults.

In this guide, we aim to educate facility managers and property owners on a variety of topics relating to TPO roofing, including its advantages, limitations, installation methods, material cost, life expectancy, maintenance and repair, and more.

Lastly, we explore the many advantages of restoring TPO with elastomeric roof coatings.


Table of Contents


Attention! Is your TPO roof in need of immediate repair? Click here to schedule your free roof inspection with an American WeatherStar Approved Contractor.

What Is TPO Roofing?

TPO (Thermoplastic Polyolefin) membrane is made up of multiple synthetic polymers and reinforcing fabric scrim, which provides the material with superior strength and performance.

TPO has only been around since the early 1990s, so it is a relative newcomer to the commercial roofing industry. It is categorized as a single-ply roofing membrane, which basically means it is installed to roof substrates in a single layer.

TPO is most often mechanically or chemically fastened to roof substrates with seams that are specially designed to be heat-welded together. It is most common on low-slope flat roofs and is popular in both the commercial and residential markets.

TPO membranes are manufactured in rolls at widths of 4, 6, 10, and 12 feet and at thicknesses of 45, 60, and 90 mils (1-mil equals 0.001 inches). Thicker TPO membranes generally last longer, but membrane thickness doesn’t necessarily equate to superior quality (more on this below).

TPO is most commonly white in color, but is also available in gray, black, tan, and various other shades. Alternative colors do provide sufficient UV protection, but they do not offer the same degree of reflectivity as the bright-white variants.

Top manufacturers of TPO include GAF, Firestone, Johns Manville, and Carlisle-Syntec, but there are many other lesser-known manufacturers, as well.

The Advantages of TPO Roofing

Cost-Effective

TPO is less expensive than many other commercial roofing materials. Its price point is undoubtedly what makes it such a popular choice in the commercial roofing industry.

Flexible & Durable

TPO is a highly flexible and durable roofing membrane that is specifically designed to withstand extreme weather and UV exposure. It is also fairly resistant to punctures, impact damage, water damage, biological growth, and dirt build-up.

Energy Efficient

TPO systems provide a highly reflective and UV resistant finish that significantly reduces roof surface temperatures and cuts down on interior cooling costs during warmer months.

Easy To Install

TPO is a lightweight material that is easy to maneuver around on roof surfaces. This important benefit significantly reduces installation time and labor costs.

Additionally, wider sheets reduce the number of seams that must be welded. This too can dramatically shorten the installation process.

The Limitations of TPO Roofing

Longevity Concerns

There is some question as to exactly how long TPO roofing systems last, but most estimates are between 10 and 25 years. As a relatively new addition to the industry, the manufacturing process of TPO varies significantly. As a result, many lower-quality membranes exist in the market.

Excessive Heat Loads

Excessive heat on TPO membranes can cause the seams and flashings to pull apart and cracks to form within the material. It can also cause the laminated top layer to deteriorate prematurely, thus making the membrane far more susceptible to damage.

Quality Variations

As a newer single-ply membrane, TPO formulations are still being perfected so material quality can vary greatly from one manufacturer to the next.

The Installation of TPO Roofing

For an average size commercial roof (20,000 sq. ft.), the installation of a TPO system should take no longer than 1–2 weeks, however, if the existing substrate and insulation must be torn off and replaced, this process could take considerably longer.

Many other factors can affect the duration of a TPO installation as well, including roof size, construction/complexity of the roof, number of penetrations, installation method, inclement weather, etc.

Below, we break down the installation process for TPO roofs.

Simple diagram of TPO roofing system

Insulation

First, insulation must be added to the roof surface. This important step provides TPO roofing systems with greater thermal resistance, or R-value (the measure of heat flow through a material). The higher the R-value, the better the insulator.

Most roofing insulation is manufactured into large rigid boards that are mechanically or chemically attached to roof decks or substrates. The boards are configured across the roof surface in a parallel fashion with staggered and tightly butted joints. They are also tapered along certain areas to ensure proper drainage.

The types of insulation include:

  • Polyiso (Polyisocyanurate) is the most widely used type of insulation for commercial roofing applications. It has a high R-value per inch, but it typically costs more than other types of insulation board.
  • EPS (Expanded Polystyrene) has one of the highest R-values among foam insulation boards and is used in a variety of building construction applications including walls, ceilings, floors, building facades, etc.
  • XPS (Extruded Polystyrene) is mostly recognized for its pink, blue, and green coloration. It is a dense, lightweight, and semi-permeable foam material developed with superior water resistance.

For some TPO roofing applications, multiple layers of insulation may be required to achieve certain state-mandated energy ratings.

Cover Board

In some cases, a cover board must be installed between the insulation layer and TPO membrane. This depends on the type of insulation used for the project.

A cover board is a thin yet durable substrate to which roofing membranes are adhered. Its primary purpose is to protect the relatively frail insulation material from hail, wind, and fire damage.

TPO can be applied directly to polyiso insulation without the use of a cover board. With EPS and XPS insulation, a cover board is typically specified by the manufacturer.

TPO Membrane

Next, the TPO membrane is secured to the substrate or cover board. This is typically done one of two ways: mechanically fastened (with screws and plates) or fully adhered (with a bonding adhesive). There are various other methods for the attachment TPO membranes, as well.

Using a heat gun and seam welding machine (pictured above), all seams and accessories are then heat welded together to form a monolithic and watertight roofing membrane.

How Much Do TPO Roofs Cost?

TPO roofing systems cost anywhere from $3.00 to $9.00 per square foot. This can vary significantly depending on a variety of factors such as:

  • Size of the roof
  • Condition of the existing substrate/insulation
  • Choice of insulation material
  • Thickness of the TPO material
  • Installation method (mechanically attached or chemically fastened)
  • Number of penetrations, drains, skylights, etc.
  • Access to the roof
  • Type of warranty

As previously mentioned, the quality of TPO can vary greatly depending on the manufacturer, so don’t be tempted by cheaper alternatives as they have the potential of being lower quality. Only consider TPO that is manufactured and supplied by reputable and well-established companies.

Below, we compare the cost of TPO against other commonly used roofing materials:

Material Low-end cost (per sq. ft.) High-end cost (per sq. ft.)
TPO $3 $9
EPDM $4 $10
PVC $5 $12
Metal* $3 $15
Modified bitumen $5 $12
Built-up $6 $14
SPF $5 $8
*The cost of a commercial metal roofing system varies significantly depending on panel profile type.

How Long Do TPO Roofs Last?

While there is some debate regarding the longevity of TPO membranes, by most estimates, they last anywhere from 10 to 25 years.

As a relative newcomer to the industry, TPO is somewhat of an unproven commodity in comparison to alternative flat roofing materials.

Additionally, many facility managers and property owners are led to believe that thicker TPO membranes equate to longer life. This is a bit of a misnomer. When it comes to life expectancy, manufacturer quality trumps material thickness.

As with any new technology, it can take time to work out the kinks. TPO is no different. Great advancements have been made in TPO technologies in recent years, so the vast majority of TPO manufactured today is predominantly good.

TPO vs Other Single-Ply Membranes

For the sake of argument, let’s see how TPO roofing membrane compares to its two biggest single-ply rivals—EPDM and PVC.

TPO vs EPDM

Next to TPO, EPDM has the greatest market share among all other single-ply membranes.

EPDM (ethylene propylene diene terpolymer), also referred to as EPDM rubber, is a highly durable and flexible roofing membrane that is comprised of synthetic rubber compounds.

Like TPO, EPDM is made into rolls of various widths and material thicknesses.

Perhaps the greatest advantage of EPDM over TPO is that it can last up to 30 years or longer.

The most obvious difference between the two membranes is their color. The vast majority of EPDM is black, but it too is manufactured in a variety of other colors including white, gray, and tan.

Black EPDM membranes are not as reflective as their bright white TPO counterparts. This particular trait is not ideal for warmer climates as it can greatly increase the heat loads put on roof surfaces.

Conversely, EPDM roofing systems are the preferred single-ply solution in most northern climates as they retain more heat during the colder winter months.

From a cost standpoint, EPDM is slightly higher than TPO, but EPDM is widely considered to be the better value because of its comparatively longer lifespan.

EPDM roofing systems are prone to shrinkage over time and their adhesively bonded seams are not quite as strong as those of TPO systems.

TPO vs PVC

PVC is another widely used single-ply membrane. Often referred to as the original weldable sheet, PVC has been around considerably longer than TPO.

PVC stands for polyvinyl chloride. Like TPO, it is a thermoplastic, heat-welded, and bright-white single-ply roofing material. PVC and TPO look almost identical—so much so that it can be difficult to tell the two materials apart from one another.

PVC is an extremely flexible, UV stable, and weather-resistant roofing membrane with a lifespan of about 20+ years. TPO and PVC are equally reflective and easy to install.

PVC is also manufactured in a variety of colors—mostly grays and tans.

PVC holds up better to intense heat and has superior resistance to grease, fumes, oils, and other chemical substances. This makes it the preferred single-ply roofing solution for the foodservice industry.

Unlike TPO, PVC has a proven reputation in the commercial roofing industry and does not carry the stigma of having lesser-quality variations tainting the market.

The primary drawback of PVC is that it is generally more expensive than TPO, as well as most other types of single-ply membranes.

PVC has a tendency to shrink as it ages and is also prone to cracking in colder weather. The National Roofing Contractors Association (NRCA) recommends avoiding foot traffic on PVC roofs if outside temperatures fall below 50°F.

Recommended reading: Commercial Roofing Systems: How They Compare

TPO Roof Maintenance & Repair

TPO is a highly effective roofing material, but it doesn’t stand a chance without regularly scheduled maintenance and properly conducted repairs.

Routine maintenance is an essential, easy, and cost-effective way to ensure the performance and longevity of a TPO roof. The purpose of any roof maintenance program is simple—catch small problems, and repair them, before they become big ones.

For more information on establishing a commercial roof maintenance program, click here.

What Causes TPO Roofs to Fail Prematurely?

Most problems that arise on TPO roofs originate around the seams and flashings. This is mostly due to exposure and the natural expansion and contraction (thermal movement) of the roof structure as internal and external temperatures fluctuate.

Over time, the excess movement causes seams and flashings to pull apart. As a result, tiny openings begin to form in the roof surface enabling water to enter the roofing assembly.

Excessive heat loads and improper installation can further compound this problem.

As a single-layer roofing membrane, TPO is also susceptible to sudden damage caused by hail, wind-driven debris, equipment additions, and trade damage.

Lack of general maintenance is also a common contributor to the rapid decline—and eventual failure—of a TPO roofing system.

Inspect Often and Repair Accordingly

The best way to avoid problems on a TPO roof is with routine inspections. Roof inspections, sometimes referred to as roof surveys, are an integral part of any maintenance program and should be performed on TPO roofs at least twice a year (in the spring and fall).

In a nutshell, the purpose of a roof inspection is to determine:

  • Signs (or sources) of roof leaks
  • Age of the existing TPO membrane
  • Condition of the seams and flashings
  • Saturation levels of the insulation layer
  • Condition of the roof decking

Inspections should also be performed soon after episodes of severe weather (hailstorms, heavy rains, high winds) and rooftop service work.

Side note: To learn more about what all is checked during an inspection, click here to download our 40-point roof maintenance checklist.

TPO Roof Repair Options

Once problems have been identified on a TPO roof, immediate action is recommended. This is the best way to avoid more extensive and costly repairs later on.

Properly repairing a TPO system requires highly specialized tools and materials and should only be performed by a certified TPO roofing contractor.

For superficial damage (small punctures, splits, tears), repairs can be made quickly with an industrial-grade roofing mastic or sealant. This type of repair is only meant as a temporary fix until a more permanent solution can be implemented.

That’s where a roof patch comes in (pictured below).

A roof patch involves the application of small sections of TPO material to affected areas. In cases of minor damage, this is the most appropriate and long-lasting repair technique for TPO roofs. Most commercial roofers even provide warranties for these types of repairs.

If the damage to a TPO roof is more severe or widespread, more extensive measures are going to be necessary. In these situations, determining the best repair option depends almost entirely on the level of saturation within the roofing insulation.

These options include:

  • Restore: If saturation levels are negligible, a roof restoration system—or roof coating system—is likely the best course of action (more on this in the next section).
  • Re-cover: Also known as re-roofing or a layover, a re-cover involves the addition of a new TPO roofing system directly over the existing membrane. Like restoration, saturation issues need to be at a minimum for this to be a suitable option.
  • Replace: If the roof has become too saturated, a complete tear-off and replacement of the TPO membrane and insulation is the only viable choice.

Another Option: Spray Foam Roofing

Spray polyurethane foam (SPF) is a great alternative for TPO roofs. It is a highly durable and energy-efficient roofing solution with the greatest R-value (thermal resistance) of any other roofing material.

Spray foam systems are applied in liquid form directly to roof substrates. As the foam cures, it hardens to form an incredibly dense, yet lightweight insulation membrane. The foam layer is then top coated with an elastomeric roof coating to protect it from the sun’s UV rays.

SPF is considered both a “re-cover” and “replace” option as it can be installed directly over existing TPO membranes or used as a replacement roofing system.

Additionally, SPF roofs can be recoated numerous times (every 10–15 years) throughout their lifespans.

Recommended reading: Spray Foam Roofing: The Complete Guide

Restoring TPO with Roof Coatings

Aged TPO membranes are excellent candidates to receive a restoration coating system. The aging process provides a matte, semi-textured finish that is far more conducive to coating adhesion.

Conversely, newer TPO bears a slick and shiny surface that can be rather difficult for coatings to stick to. Generally speaking, in order for a roof restoration system to perform properly on TPO, the membrane should at least be anywhere from 3–5 years old.

In some cases, a primer or etching rinse may be recommended to achieve proper adhesion.

The Benefits of Roof Restoration

Roof coating systems provide a seamless and watertight membrane and are proven to stop leaks, extend life, reduce energy costs, and improve sustainability. Best of all, roof restoration cost about half as much as conventional roof tear-offs and replacements. It also provides minimal interruption during installation.

Additionally, most roof coating manufacturers offer a variety of long-term labor and material warranty options.

For a more in-depth look at the many benefits of commercial roof restoration, click here.

When is the Best Time to Restore TPO Roofs?

Ideally, the best time to restore a TPO roof is before leaks and other issues become too widespread. Commercial roofs, in general, are subjected to constant exposure from the sun and other elements, so a proactive approach is always best.

At a minimum, the roofing assembly must be structurally sound and free of saturated insulation. The existing membrane must also be age-appropriate. TPO roofs that meet these requirements are likely suitable candidates for a roof coating system.

What Type of Coating Works Best on TPO?

Solvent-based coatings such as silicones and urethanes are generally the best choices for flat and low-slope TPO roofs as they offer the greatest resistance to ponding water.

Acrylic coatings are a more cost-effective option, but they are not recommended for use on TPO roofs—or flat roofs in general. As a water-based material, acrylics will break down rather quickly in ponding water.

Click here to learn more about the various types of commercial roof coating.

TPO Roof Coating Systems We Provide

  • Ure-A-Sil: The Ure-A-Sil System (our flagship system) combines the superior strength and adhesion qualities of aromatic urethane coatings with the unsurpassed UV stability and waterproofing protection of silicone coatings. Click here to learn more about Ure-A-Sil.
  • Envir-O-Sil: The Envir-O-Sil System is comprised of advanced, high-solids, low VOC silicone coatings. It is the preferred eco-friendly roof restoration solution for areas governed by strict environmental regulations. Click here to learn more about Envir-O-Sil.

To learn if roof restoration is right for your business, click here to speak with an American WeatherStar Approved Contractor near you.

Conclusion

TPO offers many advantages. If properly installed and maintained, it can last a very long time and will continually deliver UV protection and energy-efficient performance.

If you’re considering a TPO roofing system or would like to learn more about any of the topics covered in this guide, click here to speak with an American WeatherStar Customer Service Representative.