(4 minute read time)
When encountering a flat roof, it is important to treat these situations with particular care. It won’t work to use conventional shingles on these areas as the gaps in the shingles will create leaks and void the manufacturing warranties. So what are the different types of low slope roofing applications and when should each one be used?
Modified Bitumen Roofing
By far the most common type of flat roofing application that you will see in residential situations is Modified Bitumen. Modified bitumen is a two ply system that consists of the base sheet and the cap sheet. Both of these layers are self adhering, meaning the back of the material is adhesive which allows the base sheet to stick to the decking and the cap sheet to stick to the base sheet. Because of this self adhering element, torching is not required making it ideal for residential applications as it lowers liability and does not require special insurance coverage to install.
TPO Roofing
TPO (thermoplastic polyolefin) is the most common application on commercial flat roofs. TPO can be installed via self adhered or mechanically fastened methods. Self adhered is applied with sealant on the underside of the material and torching the seams while the mechanically fastened method involves screwing plates into the material on the seam line and covering it up with the next layer of material. The advantages of TPO over mod bit is that the material stays cooler which keeps the roof lasting longer. Additionally the fact that seams are torched and the material is fastened more securely also adds to longevity.
The reason it is not typically used in residential applications is that it is costs more than mod bit and also the smoother material makes it more susceptible to being punctured which is not an issue on a huge commercial building with clear skies above but would be a problem on residential roofs where tree coverage could create puncture risk when debris falls.
EPDM Roofing
EPDM (Ethylene Propylene Diene Monomer) is also used primarily in commercial applications, although it can be found on residential homes as well. It is comparable in price to TPO, but comes with its pros and cons. The benefit of EPDM over TPO is that it is a thick rubber product making it more durable against punctures, however the downside consists in the fact that being black rubber vs white plastic attracts heat more than TPO making it a less energy efficient option. Use EPDM in applications where you need coverage on lots of square footage that features lots of potential for debris which can create a puncture risk and use TPO when these risks are not present and you want to maximize energy efficiency.
Standing Seam Roofing
While metal roofing is not the most common flat roofing application, standing seam can be used in low slope applications particularly when you want a nice looking accent finish. This can include situations like porches, sheds, cabanas and pergolas. Comparable in price to TPO and EPDM it is not typically used to cover large areas of commercial roofing since the inflexibility of the metal does not make it suitable for properly waterproofing the retaining wall typically found on large commercial buildings. Additionally, while the seams will hold up for decades in an area that receives low foot traffic, in commercial applications where people need to access the roof frequently for maintenance, the seams are susceptible to being bent over time if they receive abuse over the years.
Conclusion
If you are looking to roof a low slope residential roofing situation, Modified Bitumen will most likely be the best method to use. For commercial roofing, it will likely be TPO or EPDM. However, this rule of thumb is just general guidance based on what we most commonly see so it is wise to get a professional opinion before jumping into a flat roofing project. As always, you can call us at 210-417-7728, or contact us and we’ll be happy to help!
