Advantages of Single-Ply Membranes
By only using a single layer of waterproofing all single-ply systems use fewer materials, making them comparatively cheap. The single-layer also allows for a faster installation time. Installation is relatively easy, requiring less training for contractors and fewer specialist tools. The single layer of thin material also minimises the thickness of the roof construction and the materials themselves are lightweight.
In addition to these shared traits, each membrane has its own individual advantages.
EPDM comes in very large sheets meaning there are fewer seams.
PVC is available in a lot of colours, is extremely flexible and has additives to increase its fire resistance and UV protection. A seam can be easily heat welded.
TPO is an excellent heat reflector, especially when the white coloured option is used.
It incorporates a laminated top layer of UV protection and fire-resistant additives. It can be heat-welded at the seams by skilled installers.
TPE is basically an improved version of TPO. It is UV stable and fire-resistant throughout. It is more forgiving of dust and dirt when heat sealing, improving seam strength.
Disadvantages of Single-Ply Membranes
Using such thin materials has a significant drawback, all single-ply roof membranes are extremely easy to puncture. This means that they cannot withstand foot traffic and seriously inhibits maintenance access. Having only one level of adhesion, being directly installed onto the roofing substrate, and combined with their light weight makes them very susceptible to wind uplift, particularly on poorly sealed seams. If the system is chemically adhered to the roofing substrate then, due again to the thin construction, the adhesives used can degenerate quickly due to UV and thermal heating. As a result of these issues, the lifespan of single-ply roofs can be surprisingly short.
Perhaps the most obvious and significant disadvantage that they all share is the very fact that they are single-ply membranes. There is no built-in redundancy within these systems; any puncture, faulty seam or other failures in the membrane will immediately lead to water ingress into the roofing substructure and the building itself.
Another disadvantage is that a single layer of membrane does not allow the roofing details to be independently waterproofed, allowing the roof to be compartmentalised section by section which reduces the risk of whole roof failure in the long run.
In addition to these shared traits, each membrane has its own individual disadvantages.
EPDM has no UV protection, leaving it extremely vulnerable to early degradation, shrinking and stretching. Seams are joined with a primer and adhesive which has a tendency to fail quickly. Seam failure is so common that some systems incorporate an additional cover tape adhered over the seam, but this too is prone to failure when it laps a perpendicular seam or over laps more cover tape. This susceptibility to seam faults means that it copes poorly with complex roof details. EPDM is not fire-resistant and has very poor resistance to oils, fats and grease.
PVC contains plasticiser. This will leech over time leading to shrinkage which can cause seams to fail and cause lifting from the roof substructure. It also causes the PVC to become very brittle over time and in cold weather, it is known to shatter causing the roof to fail.
TPO cannot be heat welded successfully when dusty or dirty, which can be very hard to maintain during installation, leading to an increased likelihood of seam failures. It is susceptible to damage from thermal heating, resulting in shrinking which again leads to failures at the seams and lifting from the roof substructure. The laminated top layer that provides its UV protection and fire resistance can also introduce weaknesses making the TPO more prone to crazing and subsequent deterioration. Exposure to any petroleum-based product will cause TPO serious damage.
TPE whilst an improvement on TPO is still susceptible to thermal heating, which can lead to shrinkage and seam failure. Again, it is particularly vulnerable to exposure to any petroleum-based product which will cause TPE serious damage.