Single Ply Roofing Membrane Basics: Pros, Cons & How to

a roofer on top of a house

Over the past thirty years, single ply roofing has experienced increased popularity. However, there are some to whom TPO, PVC, EPDM, or Hypalon hold little or no meaning at all. To the uninitiated, these are the various types of single ply roofing alternatives available.

The variety of hints at the excellent flexibility single ply roofing offers to the consumer. Their adaptability, environmental friendliness and superior resistance to ultraviolet rays, have endeared them to many owners and roofing contractors, despite being singularly suited to a low slope roof.

What Is a Single Ply Roof Membrane?

As can be deduced from the name, single ply roofing systems are a type of roofing material with a single waterproofing layer between the structure and its elements. Although one category, it is huge and contains diverse subcategories. The only similarity between the different types of roofing technologies within the single ply roofing category is the single membrane. In every other respect, particularly the components, they are different.

Types of Single Ply Roofing Systems

1. Thermosets

Thermosets are those roofing membranes that require tape or contact cement to lap since hot air welds tend to change their physical characteristics. Thermoset membranes are compounded rubber polymers such as ethylene propylene diene monomer (EPDM). Such membranes can be re-enforced to increase resistance against tears.

With minor adjustments, such as the application of white acrylic coatings, carbon black and titanium dioxide, EPDM single ply roofing membranes can replicate the characteristics of thermoplastics. Hypalons, although largely thermosets have a manufacturing process similar to thermoplastics. However, due to the lengthy curing time, they become thermosets. Unlike thermoplastics, however, they are un-weldable with age.

2. Thermoplastics

Thermoplastics allow for the use of Hot air welding for overlapping seams to laps. This is because, unlike thermosets, they revert to their original type upon cooling. The most common thermoplastic single ply roofing membranes are PVC (polyvinyl chloride,) and TPO (Thermoplastic Polyolefin). Most thermoplastics include a reinforcement layer, usually of fiberglass or polyester.

This increases dimensional stability and strength of the membranes. Due to their characteristically light colors, they offer reflective features that are energy saving. There are many manufacturers of single ply roofing systems. Each manufacturer has their unique manufacturing process, material mix formulation, and warranty clauses. With TPO’s, the complexity is compounded further. Due to their recent entry into the market, TPO’s are subject to much dynamism due to constant and wide-reaching research.

What to Expect

Due to their diversity, installing single ply roofing systems will present varying costs. Some of the factors that will determine the installation costs are listed below.

  • Type of single ply roofing selected.
  • Roofing deck required.
  • The level of detailing needed.
  • The level of flashing required.
  • The Attachment method selected.
  • Insurance and warranty add-ons required.
  • Building and energy code requirements.
  • Associated labor costs.
  • The job site location.
  • Nature of project (is it a re-cover or tear-off?).

Pros and Cons of Single Ply Roofs

a single ply roofing system

Pros of Single Ply Roofing Systems

  • Can take long-term punishing weather fluctuations, ozone, and ultraviolet rays.
  • Easy to install and less labor intensive since they come in huge rolls, easy to fasten with minimum labor.
  • Lower inherent risk compared to more complex built-up roofing systems.
  • Lightweight material offers flexible solutions suited to the complex architectural roof designs.
  • Energy conservation due to their reflective qualities.
  • Due to the use of recycled rubber in their manufacture, they are environmentally friendly.
  • Familiar to designers and installers.
  • Proven track record due to its longevity in the market.
  • Easily accessible at any supplies store.
  • Fire retardant, especially the PVC.
  • Cost effective.
  • Excellent for acid rain conditions and the presence of chemical materials.
  • Generally light in weight.

Cons of Single Ply Roofs

  • Loss of redundancy which is inbuilt in multi-ply roofing systems.
  • Flashings are a major concern.
  • Leaking may occur due to undetectable microscopic holes.
  • If installed on wrong substrates such as polystyrene and asphalt, the plasticizers may leach out.
  • Susceptible to low temperatures and punctures.
  • Due to the natural loss of plasticizers, they tend to shrink and crack lowering their lifespan.
  • Some, like the TPO, have questionable longevity.

How to Install/Fasten

There are three fastening methods when it comes to single ply roofing membranes. These are mechanical fastening, adhered systems or ballasted systems. When deciding upon an installation method, one must consider the roof deck type. Is the deck wooden, concrete or metal?

Chose a membrane and fastening approach that is suited to the roof deck. The method of attaching overlapping seams to one another is the most crucial aspect of any single ply roofing system. This method will determine approximately 99% of the leaks. In so doing, it will also determine the longevity, ease of repair and reliability of the roof.

1. Mechanical Fastening

Most manufacturers will give clear guidelines on fastening. Fastening through insulating concrete to the structural deck is preferred. The optimal number of fasteners should be utilized to avoid chances of blow-offs. This reduces chances of pull-offs since no single fastener is overloaded. This method is not recommended for areas with high winds that can cause uplifts. For such areas, adhesive systems reinforced with mechanical attachments are preferred.

2. Fully Adhered

Here, the new membrane is simply adhered to the substrate, whether that is deck material, insulation or existing membrane. Over mechanical fasteners, fully adhered membranes save on labor costs and time. This is especially true for the peel and stick type membranes. Although suited to windy areas, fully adhered membranes require the substrate to which they can adhere.

3. Ballasted

This method will work with EPDM single ply roofing but not with PVC’s. Of all the fastening systems, ballasted systems tend to offer the lowest per unit cost of roofing. However, they do present a challenge when trying to locate leaks. Additionally, due to its weight, ballasted systems may not be suited to most decks. Modern architecture is highly innovative and dynamic. This calls for roofing solutions that match up. Combined with environmental and energy concerns, roofing technology has to evolve to keep up.

Let’s Recap

Thankfully, single ply roofing technologies are proving more than up for the challenge. They offer flexibility, customization, ease of access and installation and multiplicity of options suited for each unique need. With constant research and development, especially concerning TPO’s, single ply roofing technologies are proving to be the roofing materials both for now and the future. Factoring in the low costs makes this roofing option the one to beat.

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