In our overview of Flat Roofing Technologies: Part I – BUR, Tar & Gravel and Modified Bitumen, we discussed the older and in many ways inefficient types of flat roofs, that are not only outdated by today’s standards, but also have a short life cycle expectancy. Moreover, they pose numerous obstacles when it comes to repair, as discussed in our Flat Roof Repair guide.
In Part II, we will take a look at the newer, more advanced roofing technologies, and explore the advantages and disadvantages of each single-ply roofing technology commonly used today.
What is single-ply flat roofing?
There is a lot of confusion about single ply membrane roofing. Many people think that any ‘single ply’ is the answer to their flat roofing problems. This however is far from being the truth. In reality, single-ply roofing membranes have only one thing in common – that is: they are single ply, or just one layer of membrane that is a waterproofing barrier. The similarity stops there.
Membrane formulation, or the components a membrane is made of, marks the biggest difference between different single-ply products. Single ply membranes come in various widths, ranging from 6 to over 18 feet. In theory, the wider the membrane is, the less overlapping seam you have, thus reducing the possibility of leaks. The reality is different however, and most commonly used membranes do not exceed 10 feet in width.
The most crucial aspect to the reliability and longevity of single ply roofs is the method of attaching overlapping seams together. That is where 99% of flat roof leaks occur. Therefore, having permanently attached seams is the most important factor in the longevity of a flat roof installation. We will discuss it in more detail as we review different single ply roofing technologies.
Single-ply Membrane Installation Methods
Single ply membranes are installed either as fully adhered or mechanically attached systems, depending on each roof’s condition, installer’s preferences, and other factors. Underneath the membrane, there is usually a separation barrier and/or some sort of insulation board. Most common insulation is ISO or EPS foam board. Both types have an R-value ranging from 4-R to 6-R per 1 inch of insulation thickness.
Mechanically attached installation uses heavy duty screws and barbed plates to hold the membrane down tightly, and is not affected by possible ISO de-lamination. The membrane is attached using 12″ O.C. pattern with perimeter sheets attached 6″ O.C. This ensures that even the hurricane-type wind will not tear off your roof. Mechanically attached installation method does not require the use of heavy and expensive ballast, and is a preferred choice, if your building is located in a high-wind area, such as along the coast line or on a high hill.
Fully adhered single ply membranes are glued to the fiberglass sheet, laminated to both sides of the ISO insulation, which is in turn attached to the roof deck. While quick and simple, the fully adhered method has one serious disadvantage. If condensation forms underneath a roofing membrane, which often happens and may be caused by improper ventilation of the roof deck, it will ‘de-laminate’ the ISO board and/or adhesive that is holding membrane in place. If the membrane becomes loose, it is prone to wind blow-off, which will leave your roof unprotected. Results of such blow-off will be catastrophic not only to your roof, but to the entire building. While this is rarely the case, it is still a possibility – a gamble you might not want to take.
More common problems with fully-adhered single-ply flat roofing systems (Mostly EPDM rubber) are defects in glue/adhesive application that cause bubbles, badly glued seams and as a result, a very unpleasant view and more often then not, roof leaks. The image bellow demonstrates a defective EPDM rubber application.
Find out more information on why you should avoid installing EPDM rubber roofing on you home and how residential roofing contractors are trained to install rubber roofs.
Three most common single-ply roofing systems
Today, when it comes to flat roof replacement, single ply roofing is the top choice. More and more contractors are switching from old systems, such as BUR, Asphalt, and Tar & Gravel to single-ply membranes, which are easier, safer and faster to install. Single ply roofing installation does not require torching, used in Modified Bitumen installation, and therefore there is no fire hazard/possibility to burn down your home / business.
There are 3 most-used single ply membrane systems present on the market today: PVC/CPA, EPDM rubber and TPO. Bellow, we provide a brief summary of each of these systems.
PVC (CPA) Roofing
- PVC – Polyvinyl Chloride – a thermoplastic membrane, utilizing a reinforcement scrim between the two plies of equal thickness (IB roof only). Top ply contains Cool Roof pigments, UV stabilizers, and other components to extend the life of the membrane. Bottom ply contains PVC ingredients to provide consistent weld of top and bottom plies and fillers. Material Warranty Period: Up to 25 years Commercial / Lifetime Residential. PVC life expectancy: 30+ years. The reason for PVC’s superior durability and longevity are the seams, which are hot air welded and as a result will be impervious to leaks and will never come apart.
- Special Notes: For a complete overview of IB flat roofing products for residential, commercial and restaurant use, as well as installation method and roofing accessories refer to our IB Roof products page.
Learn more about IB’s outstanding single ply flat roofing membrane, its advantages, and many choices for Residential, Commercial and Restaurant use.
- TPO – Thermo Plastic Olefin – a thermoplastic membrane utilizing a reinforcement scrim between the two plies. 35/65 % thickness for top & bottom ply respectively. Top ply contains Cool Roof pigments, UV stabilizers, and other components to extend the life of the membrane. Bottom ply contains TPO ingredients to provide consistent weld of top and bottom plies and fillers. Note that the top ply is about half the thickness of the bottom ply. Yet, the top ply is the one that makes the roof long-lasting. IB PVC has a 50/50 or equal thickness of top/bottom ply.
- Material Warranty Period: Up to 20 years Commercial / None for Residential. TPO roof system life expectancy – 7 to 20* years. Like PVC roofs, TPO systems also use the hot air welded seams technology to make the roof durable and leak free. However, problems with the membrane formulation, are a source of many issues. You should know that there is not a single TPO installation in existence in the USA, that was produced in North America and is older than about 15 years. Therefore it is unknown how long a TPO system will perform without any leaks*.
- Special Notes: * TPO roof systems are under continuous development by numerous manufacturers, who constantly change the TPO formulation to achieve the lowest cost with acceptable performance. While it is understandable that businesses always look to save money and to reduce costs, this ongoing TPO development process is being conducted, often at the expense of the roof owner. A TPO roof from the same manufacturer will most likely NOT be the same as the one produced a few years before or after. Also, the quality of different batches of TPO membranes may be questionable, as some TPO producers release the product to the end user without getting the UL and similar approvals/certification, as the formulation changes too often. Refer to our comparison article of PVC vs. TPO to find out more about the TPO problems / short-comings.
- EPDM Rubber – Ethylene Propylene Diene Monomer – a rubber-like black membrane, usually non-reinforced. Most common application method is a fully adhered (glued down) membrane with glued seams / flashings.
- Material Warranty Period: Up to 40 years Commercial / None Residential. EPDM roof system life expectancy – 10 to 15 years. Although the material warranty goes up to 40 years for a 90-mil Epdm from some manufacturers, it does not cover the seams. Failing seams are the main cause of EPDM roof leaks, followed by ponding water, for which EPDM has no warranty either.
- Special Notes: EPDM is the least expensive single ply roofing type and requires no special equipment to install it (unlike PVC and TPO which require hot-air welding equipment) and thus is the first choice for contractors entering the flat roofing market and asphalt shingle roofers, who ‘install rubber here and there’. Although many commercial roofing companies also use EPDM, they usually do not perform Residential installations so many times a home owner deals with a Part-Time flat roofing company.
Badly installed Rubber Roof:
Please note that there are many manufacturers of all three types of roofing, and each has their own formulation / manufacturing process / warranty conditions and periods, etc. Therefore we only provide a general summary for each of those roof types. Also, since our specialty is installation of IB roofs, when we use the term PVC or CPA we refer to IB PVC Roofs (CPA or Co-Polymer Alloy is the way IB Roof Systems refers to its PVC product. IB membranes are 100% ‘compatible’ with other PVC products).