With roofing, the choices vary depending on what you require. TPO roofing is one excellent option that’s typically used for many commercial roofing applications. The other commercial roofing option is Ethylene Propylene Diene Terpolymer (EPDM) which is not covered in detail here.
For this article, we focus on TPO roofing and cover how to install it and troubleshoot any potential issues with this type of roof.
What is TPO Roofing?
TPO stands for Thermoplastic Polyolefin. As commercial roofing options go, it’s quickly becoming an easy choice for business owners and commercial building owners in need of improved roofing material. According to the National Roofing Contractors Assn., just under half of all commercial roofs use TPO materials at this time.
TPO and Scrim
TPO is a membrane that is layered over the roofing structure. Also, it comes as a single-ply material comprised of various synthetics.
For flat roofing, the scrim is also commonly added to provide reinforcement. Scrim is a woven fiber material that provides additional durability and strength.
Made in Sheets and Easy to Transport
The membranes are produced in sheets that come with various width measurements. Most producers offer a 20-, 12-, or 10-foot TPO membrane that is produced in a roll ready for delivery as building supplies. They then just need contractors to install them.
One of the benefits is that TPO can reflect UV rays, avoiding the roofing and floors below from heating up in warmer parts of the country.
The Basics of TPO Roofing Installation
The installation is a task that requires a team to complete it, rather than one person. The team is required to complete the new roof in a reasonable time. This avoids added problems due to an extended installation period, including the possibility of precipitation.
Roofing Substrate is Prepared
The roofing substrate is readied first. This is done by either cleaning the existing roof in preparation for the next stage or by removing a deteriorated existing roofing material to make way for its replacement.
The replacement may or may not include the removal of any existing installation below the current roof. That will depend on its age, condition, and how suitable it will be to successfully layer over any existing insulation with TPO roofing materials.
In most cases, it’s best to start with a clean roof and use new insulation. This avoids the risks of older, inferior insulation making the TPO roof less durable or not providing all the potential benefits that the building owner is hoping for.
Insulation Comes Next
Insulation is added to the roof. This usually has a thickness of at least one and a half inches (often more than that). Only gaps between the insulation of up to a quarter of an inch are usually acceptable, ensuring that the majority of the roof is covered with the insulation material. This serves to keep the warmth in but prevents excess heat from penetrating the roof on sunny days to avoid heating the building unnecessarily.
The insulation types include:
- Extruded Polystyrene – Known as XPS in the industry, it is provided at a mid-price point and offers good performance. It comes in pink, green, or blue color and is semipermeable with a 1 perm rating.
- Expanded Polystyrene – Known as EPS, it is usable over floors, walls, and roofs too. It does not retain water, so it offers better waterproofing abilities than XPS.
- Polyisocyanurate – Referred to as Polyiso, it is perhaps the most effective of all. It usually commands the highest sticker price per foot.
A cover board is used on the roof, to which the TPO membrane gets attached or bonded to. Using boards in this manner is more practical for application purposes and avoids damaging the insulation below.
The TPO membranes are layered over the board and attached using either a special bonding adhesive agent or are fastened on mechanically instead. This is where the measurements of the TPO membrane sheets must be accurate to fit the roof correctly, otherwise it will interfere with the bonding process necessary for a successful installation.
A heat fastening plate and a heat welding machine/hot air gun are used to hot air weld all the seams together neatly. TPO and flash are necessary to create a roofing finish that appears seamless to the naked eye.
What is Roof Flashing?
Roof flashing may not be a familiar term. Roofers use this galvanized steel (sometimes other materials) to change the flow of rainwater away from sensitive areas. It’s mostly used on or around flat parts of the roof, like skylights, vents, and more, where water would otherwise pool-up.
Flashing, therefore, acts to protect roofing features from potential future moisture damage and redirects water towards flow systems such as guttering and drainage.
Are There Any Issues with TPO Roofing Materials?
You may be wondering if there are any concerns or potential issues with TPO roofing materials. Here are some things to consider.
Newer Roofing Material
TPO as a material has only been around for a decade or so. Therefore, it doesn’t have the history that some of the other roofing materials provide. Nevertheless, it’s widely used and respected.
Heat Degradation at Extreme Temperature Levels
There have been some issues of TPO degrading in extreme heat situations. Reformulations have been ongoing to provide an improved ability to withstand the hotter type of environments, such as desert heat in Arizona or the sunshine in Florida, as two examples.
However, generally speaking, only temperatures over 160 degrees Fahrenheit are potentially problematic for material protection. Therefore, this shouldn’t be an issue for most building owners.
TPO roofing is fine for commercial and residential roofing applications where it won’t be used for other purposes.
However, when a roof is being considered as a livable space with patio furniture and a BBQ, or as a roof garden, then it’s likely that TPO is a poor roofing material for this purpose. It’s flammable, so a BBQ is a total no-no too.
For commercial building owners, a TPO roof is a dependable solution when you need a new roofing material. It does require a team of installers with special equipment to complete the installation, so be prepared for that.