Flat Roof Assemblies

When it comes to flat roof assembly you many have a vague understanding of its composition and components. A flat roof assembly is a complex system composed of multiple components combined to form an integral part of your building envelope.

Conventional Flat Roof Assembly

The components of a conventional flat roof assembly varies very little from roof to roof. The main components typically remain constant, while the only component that will vary is the roof membranes (Manufacturers roof system) - which is the waterproofing barrier or top layer of the roof assembly.

The main components of a conventional roof assembly typically include:

  • Roof membrane/Roof System – The waterproofing barrier or top layer of the roof assembly
  • Cover Board – Ridged substrate utilized to adhere the roof membrane
  • Ridged Thermal Insulation – Provides a thermal barrier for interior climate control
  • Vapour Barrier – Prevents moisture transfer from interior to exterior
  • Structural Roof Deck – Sheathing laid across the structural joists/rafters (Typically wood, steel or concrete)
  • Structural Joists/Rafters – The structural component of the building that supports the roof

TPO (Thermoplastic Polyolefin) Roof System

TPO (Thermoplastic Polyolefin) was developed as an even more environmentally friendly alternative to EPDM. The single-ply membrane is a white, environmentally friendly roofing system that has strong resistance to ultra-violet radiation, weathering and outstanding seam strength. TPO is a proprietary thermoplastic polyolefin combining polypropylene and ethylene propylene rubber. The white, scrim-reinforced membrane combines the weather-ability of rubber with the heat weld-ability of a thermoplastic in a highly flexible sheet with excellent lay flat characteristics. TPO can be installed either fully adhered, mechanically attached or ballasted, with the seams of the roofing system heat welded to form a strong homogenous bond.

Benefits of utilizing TPO as a roofing solution are:

  • Extremely resilient and unaffected by environmental exposure and degradation
  • Extremely ultra-violet resistant and ozone stable
  • Light coloured material which reflects sunlight to improve energy efficiency of buildings
  • Long life expectancy
  • Cold temperature flexibility
  • Extremely strong seam strength
  • High puncture and tear resistance
  • Fire resistant
  • Lightweight material
  • Clean and efficient system which is 100% recyclable
  • Easily inspected and repaired (As opposed to ballasted roof systems)

EPDM (Ethylene Propylene Diene Monomer) Roof System

EPDM membrane (Ethylene Propylene Diene Monomer) is an extremely durable synthetic rubber roofing membrane widely used in flat roofing applications worldwide. Its two primary ingredients, ethylene and propylene, are derived from oil and natural gas. EPDM is available in both black and white, and can be installed either fully adhered, mechanically attached or ballasted, with the seams of the roofing system sealed with liquid adhesives or specially formulated tape.

Benefits of utilizing EPDM as a roofing solution are:

  • Extremely ultra-violet resistant and ozone stable
  • Light coloured material which reflects sunlight to improve energy efficiency of buildings
  • Long life expectancy
  • Cold temperature flexibility
  • Fire resistant
  • Easily inspected and repaired (As opposed to ballasted roof systems)

PVC (Polyvinyl Chloride) Roof System

PVC (Polyvinyl Chloride) membrane roofing is also known as vinyl roofing. PVC membrane begins formation when ethylene and chlorine are combined to produce a vinyl gas. The vinyl gas is converted into a fine powder that is then compounded. During the compounding process additives may be added to increase the durability, flexibility, and color of the membrane. PVC roofs provide an energy-efficient roof with the application of white coloured membranes. PVC can be installed either fully adhered, mechanically attached or ballasted, with the seams of the roofing system heat welded to form a strong homogenous bond.

Benefits of utilizing PVC as a roofing solution are:

  • Extremely resilient and unaffected by environmental exposure and degradation
  • Extremely ultra-violet resistant and ozone stable
  • Light coloured material which reflects sunlight to improve energy efficiency of buildings
  • Extremely strong seam strength
  • Fire resistant
  • Lightweight material
  • Easily inspected and repaired (As opposed to ballasted roof systems)

Modified Bitumen Roof System

Modified Bitumen roof systems are asphalt based and provide superior waterproofing characteristics. Modified Bitumen roofs are usually installed as a two ply system with a smooth one ply base sheet followed by a granulated one ply cap sheet finish. These roof systems are made up of asphalt that has been modified with a polymer to create plastic or rubber like properties. The modifiers provide increased resistance to brittleness, cold temperatures and increased elasticity and strength. The most common modifiers are APP (Atactic Polypropylene) and SBS (Styrene Butadiene Styrene). Modified bitumen roof systems are usually adhered with either hot asphalt, adhesives, torch applied or peel and stick applied. However, in some cases, the first layer of the two-ply system may be mechanically fastened.

Benefits of utilizing modified bitumen as a roofing solution are:

  • Heavy duty, robust and extremely tough
  • Long life expectancy
  • Cold temperature flexibility
  • Extremely strong seam strength
  • High puncture and tear resistance
  • Fire resistant
  • Easily inspected and repaired (As opposed to ballasted roof systems)

Four-Ply Built-Up-Roofing (BUR) Roof System

Four-Ply Built-Up-Roofing (BUR) roof systems are better known as the traditional tar & gravel roof system. BUR roofing consists of 4-plies of felts laminated with approximately 25 lbs. /100 sq. ft. of asphalt between the plies. A final surfacing flood coat of approximately 30 lbs. /100 sq. ft. of asphalt is applied with approximately 400 lbs. /100 sq. ft. of 3/8” pea stone ballast embedded into the flood coating.

Benefits of utilizing BUR as a roofing solution are:

  • Heavy duty, robust and extremely tough
  • Long life expectancy
  • Extremely strong seam strength
  • High puncture and tear resistance

Specialty Flat Roof Assemblies

Inverted Roof Assembly

Inverted Roof AssemblyAn inverted roof assembly is where the insulation layer is above the waterproofing layer, as opposed to a conventional roof system where the insulation is sealed under the roof membrane. An inverted roof system is sometimes referred to as the protected membrane roof and utilizes a special extruded insulation which is designed to withstand exposure to the elements. Inverted roof systems are always ballasted with stone or precast concrete pavers. Inverted roofs are designed to accommodate heavy duty commercial and industrial roofing applications where the roof is exposed to tremendous stress.

Green Roof Assembly

green roofingGreen roofs are described as an aesthetically pleasing way to lower the carbon footprint of a building at the same time as raising environmental standards, providing more efficient insulation, producing lower energy bills, improving air quality and alleviating problems of storm water management. See Green Roofing for further details.