The two most commonly used roofing systems in commercial properties are TPO and modified bitumen. Modified bitumen roofing has been around since the 1970s and TPO developed later in the 1990s. Both offer a durable waterproofing membrane that protects against weather and other elements, but there are differences between the two materials. Each system has its own advantages and disadvantages, which makes it important to carefully consider your choice before installing a roofing system.

TPO vs. Modified Bitumen: What to Choose?

Modified Bitumen Roofing

Modified bitumen systems are practical and lower in cost than other commercial roofing options. Bitumen was an upgrade from traditional systems and offered enhanced longevity and flexibility.

Advantages of modified bitumen may include but are not limited to:

1) The ability to accommodate thermal expansion and contraction.

Because of its flexibility, this type of roofing can accommodate temperature fluctuations that result from outdoor weather.

2) Resistance to the chemicals found in air pollution.

Most modified bitumen systems are resistant to corrosive chemicals like sulfuric acid and sodium hydroxide. This is a significant advantage over other commercial roofs.

3) A lower price point.

Modified bitumen roofs tend to be less expensive than other commercial roofing options. This is because it is a relatively simple process, and there are fewer materials than most other commercial roofing products.

4) Better resistance to the sun and rain.

Modified bitumen roofs are naturally water-resistant and can even thrive in areas with heavy rainfall. This is because it is manufactured with a black top course. The black course helps to maximize the flow of heat away from the roof, making it more resistant to damage caused by ice and water.

5) An easy-to-install system.

Since this system is relatively simple compared to other commercial roofing options, it can usually be installed very quickly. This makes it much more affordable for customers who are on a tight budget or time frame.

However, many contractors have stopped offering these systems due to a number of disadvantages that were recently discovered.

Modified bitumen roofing was designed to improve the original version by adding substances like APP (atactic polypropylene). This made sure that the newer systems were resistant to UV light, oxidation, cracking, and blistering. Unfortunately, some manufacturers do not use enough APP to save money and this means the modified bitumen roofing doesn’t stand up to newer challenges as well as expected. The granulated surface of these systems was also added to provide additional UV resistance but makes it more difficult to identify cracks and leaks on the surface. These roofs also come with a serious fire hazard if there are any open flames nearby during installation.

Most of the modified bitumen roofing on the market has a limited warranty, which means that it may not last as long as other commercial roofing options. The warranties for these systems usually cover leaks but do not include blistering or delamination for between ten and fifteen years. Any damage caused by wind will not be covered.

Like any type of roofing, modified bitumen roofs require regular maintenance to stay in good condition. The surface of the roof must be cleaned at least once a year and corrosion on metal connectors may also need to be repaired.

This system is no longer widely used because of its disadvantages but some contractors still offer this type of roofing. Modifying the original version does not appear to have solved the problems with this system.

TPO Roofing

Thermoplastic Polyolefin (TPO) roofing is the more modern choice in large-scale roofing and is installed typically in one of three ways; ballasted, mechanically fastened, and fully adhered to. It has become popular because of the numerous benefits for building owners.

Ballasted installation involves placing the horizontal TPO strip over a base layer of waterproof felt. The material is stapled to the roof decking before ballast (rocks or gravel) are laid on top. This type of installation provides protection against UV damage, resulting in lower costs for building owners. If properly installed, this system can last up to 20 years.

Mechanically fastened installation is more similar to conventional asphalt roofs and involves the TPO sheets being mechanically attached to the roof decking with screws. This process can add up to two extra layers of protection but also requires special care during installation because if any of the screws are missing, they may puncture or tear through the material.

The fully adhered installation uses a special flashing membrane attached to the roof decking before being fully bonded with hot asphalt. The tape also provides extra moisture protection and is designed to attach tightly, provided there is a good base for the adhesive to grab onto. This system can last up to 25 years under heavy weather conditions.

The single-ply membrane is tear-resistant, UV resistant, and resistant to chemical and grease spills. They are also fully recyclable which is popular with today’s more eco-friendly society. There are also no plasticizers in the insulation which adds to it’s “green” image and appeal. You can also pick from an assortment of colors to match your building or opt for the traditional and energy-saving white. If the current roof is in good condition, you can apply TPO over existing metal or bitumen roofing.

Additionally, installation is fast and easy. Compared to traditional roofing materials, TPO flat roofs are waterproof within an hour of installation. A rubber mallet or roller is used to seal the seams at the top of the sheet. Besides durability, it also has a low-cost construction process.

TPO roofing offers great benefits for building owners but there are some precautions you must take when deciding to install this type of roofing on your commercial property. It can be used as a single-ply membrane surface or as a multi-layered system.

You must always ensure that your roofing system is installed correctly as most of the problems detected with TPO systems have to do with poor installation. With quality and an experienced roofer that installs the system and welds the seams correctly, you can be assured that your TPO roofing will be more effective and will last longer than expected.

TPO and Modified Bitumen: Maintenance

One of the major factors to take into account when choosing a roofing system would be its maintenance. A well-installed roof doesn’t mean that you don’t need to take care of it anymore. You should always check your roofing system regularly for any damage, leaking, or other problems in order to avoid major repairs in the future.

For both roofing options, make sure you hire a professional roofer to inspect your system on a regular basis. A regular inspection is done every two to three years in commercial buildings and once a year for industrial roofs. For flat roofs, the owners of industrial or commercial properties should hire a professional roofer every six months to inspect the system.

TPO Roofing Maintenance Tips

1) Inspect your roofing system regularly to check for any insulation, tiles, or seams that have been torn. These damages and problems must be fixed immediately before they can spread or cause more damage to the roof.

2) You should also check that the roof’s watertight seal is still working correctly. Look for cracks, changes in color or texture, or other damages to know whether this system needs maintenance.

3) If there are any missing tiles, find out if they can be fixed by replacing just one tile or if you need to replace the whole section of your roof. Also, check around the peak of your property where the sheets meet to ensure that they are sealed perfectly and don’t have any gaps between them which could cause problems with moisture penetration. This could result in long-term leaks and potential damage to your insulation and decking.

4) Ensure that your roof is well-ventilated to limit internal condensation which can lower your roof’s life expectancy. Look for cracks, missing material, bent sheets, and other areas where the ventilation is no longer optimal.

5) Remember that TPO roofs are very sensitive to damage caused by hail. Although it has a thick built-up surface that can withstand hailstones up to 1 inch in diameter, your roofing system will still be damaged beyond repair if you get struck by large volumes of hail over time. If this happens, you need to replace the whole roofing system since it could affect its watertight seal and structure.

6) Another way to ensure that your roofing system stays in good condition is to regularly clean dirt and dust from it especially if the top of gravel is exposed.

7) Maintaining the right temperature and humidity inside your building is also important. As we all know, hot and humid weather could cause internal condensation which can deteriorate your roofing system over time. One way to prevent this from happening is to use a dehumidifier inside your property during summer or ventilate your roofing with fans and open windows during the winter and fall seasons.

Modified Bitumen Maintenance Tips

1) Inspect the roofing system regularly for any damage, leaks, or other problems.

2) Check your roof periodically for debris carried by the wind. Wipe it clean to avoid rust on metal sheets.

3) Ensure that your waterproof membranes are still in place and have not been penetrated or damaged by sharp objects which could cause major damage to these components.

4) Also check if there are any damages to the adhesives used at the seams since these are what make your roofing system watertight. If needed, ask a professional roofer for help with this task.

5) Try and limit long-term exposure of your black rubber surfaces to sunlight as they can become brittle and degrade because of ultraviolet light rays (UV rays).

6) Check your roofing system regularly for any problems with the sheathing, decking, insulation, and ventilation. The extended exposure to UV rays can cause these components to degrade faster than expected.

7) It is essential to keep your roof clean. In addition to removing dirt and dust from the top of your property, make sure you check under your eaves for cobwebs and insects that could penetrate into the insulation or decking of your roofing system.

8) Keep an eye on hot and humid weather conditions since they can cause internal condensation which affects the integrity of your waterproof membrane over time. Fans and open windows are a good idea during summer if you live in a warm climate.

TPO vs. Modified Bitumen: Final Thoughts

So what are the main advantages of TPO over modified bitumen? Considering that TPO is lighter and more flexible, it can be installed on roofs with a pitch of up to 30 degrees compared to only 10 degrees for modified bitumen. It is also less harmful to the environment since there are no toxic chemicals used in its production process.

On top of that, TPO roofing systems require fewer maintenance activities than modified bitumen but both materials come with different advantages and disadvantages depending on your needs and preferences.

In terms of cost, TPO is more expensive compared to modified bitumen. The added cost, however, can justify the improved durability and weather resistance of TPO roofing systems.

While TPO offers better insulation than modified bitumen, the latter is more resistant to tears and punctures. Furthermore, modified bitumen roofs are easier to repair or replace in case there is damage to the waterproof membrane compared to TPO where you would probably have to replace your entire roofing system.

While there are still some disadvantages in using modified bitumen roofing systems despite all their benefits over traditional materials, weighing all the options can help you choose the right product for your property, one that meets your budget and long-term expectations.

Whichever roofing material you decide to go with, we have the expertise and resources to get your new commercial roofing installed with quality and efficiency. TPO is the preferred option but we understand that sometimes traditional materials are great too. We are here to answer any of your concerns regarding your next roofing project and find the best fit for your roof.


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