Single Ply 

Currently, there are three major single-ply roof systems: PVC, TPO and EPDM.
They are then further divided into two sub categories: weldable and non-weldable.

Non - Weldable EPDM (Ethylene Propylene Diene Terpolymer): 

• Rubber sheets available in standard black or white colors
• The most economical singly-ply membrane
• Developed in the 1960's in the United States
• Ideal for ballasted, mechanically attached and fully adhered systems
• Very large sheets
• Good chemical resistance but poor oil, grease and asphalt resistance
• White reflects the sunlight & cools the buildings interior
• Typical thickness is 45 mils, 60 mils, 75 mils, 90 mils
• Sealed using special adhesives or self-adhering tapes
• Can be reinforced with tough polyester fabric for superior fatigue, tear, & puncture resistance
• High resistance to ozone, weathering and abrasion
• Flexibility in low temperatures
• Thermal shock durability

EPDM is usually used for industrial, institutional or commercial buildings.  EPDM is a roofing material made from ethylene propylene rubber.  EPDM can be installed by ballasting, mechanical fastening or full adherence.  If ballasted or mechanically applied, EPDM can be reusable; they are also durable with an average lifespan of 20 plus years.  One problem with EPDM is that they have been known to shrink in some circumstances.

Weldable TPO (Thermoplastic Polyolefin):
 

• Available in white, tan or gray colors
• White membranes reflect sunlight and cool building interior for energy savings
• Weathering stability and low temperature flexibility with superior welded seam strength
• Minimal shrinkage for watertight integrity
• Mechanically Attached and Fully Adhered System
• Lightweight yet highly resistant to tears, impact, punctures, & wind uplift
• No natural fire resistance
• Developed in the 1990's
• Typical thickness is either 45 mils or 60 mils
• Heat welded seams that are stronger than the material itself
• Can be installed during winter months and is ideal for new construction and re-roofing
• Environmentally friendly - no chlorine, recyclable
         

One of the newest flat roof roofing materials available in the market that has been getting high praises is the Thermoplastic Polyolefin Roofing Membranes or TPO.  TPO is regarded as the new-generation of single-ply roofing materials.  Even though it is "single-ply", it consists of three components or layers that make up its entirety.  It has a structural deck or the outer skin; in the middle you will find the thermal insulation barrier, then a waterproofing skin is what adheres to the roof.  Its materials are very efficient in the task at hand, they can be reusable if installed properly or applied with water or pebbles.  TPO is very durable and has low toxicity.  TPO is not recyclable, however, as it contains petrochemicals.  Since TPO has been around for only ten years, life span cannot be calculated yet.

This type of membrane is designed to combine the durability of rubber with the proven performance of hot-air weldable seams.  They have been tested as having excellent resistance to ozone, are algae-resistant, environmentally friendly and safe to install.  The material's manufacturers are so confident in properly welded seams that the material is sometimes advertised as a monolithic (seamless) roof.  Seam strengths are reportedly 3 to 4 times those of EPDM's adhesive and tape seams.  TPO is highly resistant to tears, impacts, and punctures with good flexibility to allow for building movement.  TPO's are available in white, light gray, and black with thicknesses of either 45 mils (.045") or 60 mils (.060").  The width of the membrane depends on the manufacturer but they usually come in widths of six to six-and-a-half feet and are one-hundred feet in length.

TPO membranes can be installed fully-adhered, mechanically-attached or ballasted.  Fully-adhered means that the roof is "glued" to the substrate using a special adhesive.  This special adhesive, or glue, actually creates a chemical bond with the membrane.  Ballasted simply means the membrane is loose-laid over the top of the roof, sealed at all penetrations and around the perimeter, and then a ballast is put on it to hold it in place.  Ballast usually consists of smooth, round, river rock 2" - 3" in diameter and is applied at a rate of 1,000 to 1,200 pounds per roof square (100 sq. ft.).  Sometimes concrete pavers are used in their place and average 20 pounds per square foot. Mechanically-attached membranes are those that use some type of special screw-type fastener to secure it.  The type of fastener will depend on the type of substrate but all fasteners are generally screw-type fasteners.

Weldable PVC (Poly Vinyl Chloride):
 

• Was developed in the late 1960's in Europe
• Good fire resistance, fungus, ozone & UV
• Flexibility / physical integrity to resist cracking after prolonged exposure to minus 30[degreesymbol]F
• Typical thickness is either 47 mils or 60 mils
• Heat welded seams that are stronger than the material itself
• White membranes reflect sunlight and cool building interior for energy savings
• Minimal shrinkage, a major factor affecting membrane performance and longevity
• Mechanically Attached and Fully Adhered System Specifications
• Weighs less than 1 pound per square foot yet highly resistant to wind uplift and tearing
• Can be installed during winter months and is ideal for new construction and re-roofing

Polyvinyl chloride or PVC roof membranes have the distinction of having the longest track record of usage among any thermo plastic roofing membranes.  They have been in use since the early 1960’s.  Even with the emergence of other flat-roof roofing materials, PVC is still employed by many.  The choice of PVC offers many features such as huge color variety, high resistance to perforation and impact as well as fire exposure.  It has great flexibility and tolerance to extreme temperatures.  The main problem with PVC roofing systems, in a highly ecological culture, is that they are not reusable or recyclable.  The average life-span of PVC flat-roof roofing material is twenty-five years and longer.

Single Ply Asphalt Roll Roofing

One of the most durable and flexible of all flat-roof roofing material is mastic asphalt. Mastic asphalt is recyclable, non-toxic, odorless and can withstand extreme temperatures as well as the test of time. This type of roofing system can last for over 60 years.

Rigid Insulation

Adding insulation to the roof deck is the easiest way to improve L.T.T.R. (Long Term Thermal Resistance or “R” Value).  The insulation comes in sizes from 1/2” up to 4” in thickness but multiple layers can be added on top of each other to improve your L.T.T.R.  It is also available in tapered versions to allow for drainage pitch requirements.

There are three types of Single Ply Installation:
 
Mechanically attached installations use rows of fasteners to hold the roof down.  If not in laps then cover strips are needed.  Reinforced sheet is recommended. Ballasted installations typically use #3 or #4 river-washed (rounded) gravel at 10 to 12 pounds per square foot.  We can also place any kind of brick, concrete pavers or similar type of ballast material. Fully Adhered roof installations typically uses contact-cement to adhere the membrane to the substrate.  Foam and bitumen have been used with fleece-backed membranes.  The substrate must be approved by the membrane supplier.