By Calgary Roofing | General Roofing Systems Calgary

04/24/2010 Flat Roofing


General Roofing Systems Canada installs flat roofing systems (Modified SBS, Built Up "BUR", EPDM, TPO, and PVC), on many different complexes (Commercial, Industrial, Institutional) through out Western Canada. We install new flat roofs, retro-fit others, and renovate (re-roof) complete flat roofing systems.

There are many different flat roof systems to consider. Below is an extensive flat roofing guide to assist your review.

Call us for a free estimate, or for further information your organization may require to make educated decisions anytime at 877.497.3528.

A Critical Investment
The roof is a vital part of the building and thus a substantial and critical investment. Whether you're considering the environmental benefits of green / sustainable roofing, “cool roofs”, a conventional new roof installation, or are looking for ways to extend the life of an existing roof, our expertise and commitment to quality will ensure your roof is built to last, and will extend the life of your building.

We believe in an educated client, it is our hope the following guide to flat roofing installation and renovation choices will assist you in the process of managing your roof investment.

Flat Roof Re-Roofing or Retro-Fitting (Re-Covering)
No roof will last forever – not even the very best roof. Re-roofing or retro-fitting can help maintain a healthy building and your valued investment.

Re-roofing, or full-removal of the existing flat roof system, involves removal of the flat roof surface, membrane, and insulation to the roof deck to enable to install the new flat roof.

Retro-fitting, or re-covering, covers an existing flat roof system with a new flat roof system. This process requires all wet, damaged, or deteriorating insulation be removed prior to the new flat roof being installed. Both systems are appropriate for flat roofs that can no longer be repaired through regular maintenance, are showing signs of serious deterioration, or are beginning to leak.

Flat roof re-roofing requires special attention to detail by our roofing crews. In most cases, the building will be occupied while our installers are working. We take special care to make sure the building tenants and pedestrian traffic are safe and are inconvenienced as little as possible when installing your roof.

As with all roofing installation projects, we strive to exceed industry standards for safety and quality. Your flat roof is a serious investment and proper application of a re-roofing or retro-fitting flat roof system will extend the life of your roof for years to come.

New Flat Roofing
Roofs are not installed in a controlled environment - projects have many variables. The type of material, the application, job-site conditions, and weather all affect a project. But even with all those variables, we strive to deliver a top-quality flat roof product.

In addition to our own standards for quality, you will have an iron clad workmanship guarantee, and a manufacturer's warranty, and we adhere to guidelines set out by CRCA's recommendations for roofing and flashing details.

We also pay close attention to safety. Our safety practices are designed to ensure that our staff and the other trades working on-site stay safe and healthy for the entire project and return home to their family safe and healthy every day.

Working Together
Our flat roofing division management work with project consultants, designers, membrane manufacturers, facility managers, and general contractors to achieve the best flat roof assembly and installation possible at the most fair and competitive price.

Once a contract has been agreed to and executed, we carefully review construction schedules for the flat roof installation and project details with the owner and the applicators before your roofing project begins.

Environmental Roofing Solutions
From green roofs to solar roofing installations and day-lighting, our environmental roofing solutions can help your business utilize your roof as an effective way to generate energy and harness savings.

Flat Roof Installation Options
Following is an exhaustive guide of flat roofing installations we make available to the commercial, institutional, and industrial marketplace.

1. Built up Roofing (BUR) - known also as Tar and Gravel
2. Singly Ply Membrane Roofing
a. EPDM
b. TPO
c. PVC
3. Modified Bitumen (SBS) Roofing
4. Metal Roofing
5. Liquid Applied Roofing
6. Green Roofing (Garden Roofs)


1. Multiple-Ply or Built up Flat Roofing (BUR) "Tar and Gravel"
Traditionally, flat roofs have been installed by setting 3-4 layers of asphalt-saturated felt (tar-paper) by mopping hot asphalt. Typically, the surfacing is gravel set in a flood-coat of hot asphalt. This is referred to as “conventional built-up roofing, BUR, or Tar and Gravel”.

2. Single-Ply Flat Roof Membranes
Over the years, a wide variety of roofing system membranes have been developed, using various forms of synthetic rubber and vinyl applications. The roof membrane is manufactured under controlled factory conditions. The seams are typically formed on site, using adhesives, tapes, or hot-air welding. Some roofing membranes are available in different colors, and can be manufactured in wide rolls to minimize the number of seams.

2a. EPDM (Ethylene Propylene Diene Monomer) Flat Roofing
EPDM is a single ply flat roofing system composed of a rubber membrane used on small to large commercial and industrial roofing projects. It is applied using a fully-adhered glue system, loose-laid with gravel (ballasted), or mechanically fastened - all of which require no open flame. The environmentally friendly considerations are; reduced emissions from equipment, fewer petroleum based roofing products, and less landfill waste. The system can lower heating and cooling costs with proper insulation. The product is readily available in white or black. Competitive roof life cycle costs. Less cost than a complete re-roof and is a less intrusive roof installation than most other systems.

2b. TPO (Thermo-plastic Polyolefin Roofing Membranes) Flat Roofing
A thermoplastic elastomer is a diverse family of rubber-like materials that, unlike conventional thermoset rubbers, can be reprocessed and recycled like thermoplastic materials. Thermoplastic polyolefins are in the thermoplastic elastomer family and are commonly referred to as TPO in the single-ply roofing industry.

TPO-based products are used in various applications, including the automobile industry, and have seen their usage continue to expand. Over time, TPO-based membranes moved into the roofing industry as a non-reinforced sheet. In 1993, the original non-reinforced TPO flat roof membrane was replaced with roof membranes containing reinforcing fabric. Since that time, the TPO single-ply roofing market has grown to hundreds of millions of square feet annually. TPO roof membrane is one of the faster growing segments of the single-ply roofing industry.

TPO Roofing Composition
TPO roofing membrane is typically based on polypropylene and EP (ethylene-propylene) rubber polymerized together using state-of-the-art polymer manufacturing technology. This technology enables the production of TPO membranes that are flexible at low temperatures without the use of polymeric or liquid plasticizers. Unlike some other popular thermoplastic roofing membranes, the TPO polymer does not contain chlorine and no chlorine-containing ingredients are added during sheet production. This lack of chlorine has allowed TPO roofing marketers to tout their membrane as an environmentally safe, “green” roofing product.

The TPO resin is compounded with other components including a weathering package, fire retardants and pigments for color to create a product that can withstand the elements associated with rooftop exposure. The membrane is comprised of TPO based top and bottom plies encapsulating a reinforcing fabric that enhances the physical properties of the sheet. The combination of the fabric and TPO plies provide reinforced roofing membranes with high breaking and tearing strength and puncture resistance. Sheet widths are available up to 3.66 m (12 ft) and membrane thickness is typically 1.1 or 1.5 mm (0.045 and 0.060 in.), however, roofing membrane up to 2.0 mm (0.080 in.) is available.

TPO Roofing Installation/ System Types
TPO roofing membrane is typically installed using mechanical fasteners and plates placed along the edge of the sheet and fastened through the roofing membrane and into the roof decking. Adjoining sheets of TPO roof membrane are overlapped, covering the fasteners and plates, and joined together with a minimum 40 mm (1 1/2 in.) wide hot air weld.

In the field area of the roof, proper membrane width and fastener spacing is determined after calculating potential uplift loads based on building height, surrounding terrain and the wind zone in which the building is located. The fastener/deck combination must exhibit adequate pull-out resistance to withstand the fastener loading generated during uplift. The roofing membrane and the welded seam must also resist the forces generated by wind uplift. The ability of a mechanically fastened system to withstand these forces is typically evaluated using a 3.7 x 7.3 m (12 ft x 24 ft) uplift table where the system may be pressurized until failure. Along the perimeter of the roof, where the highest wind loads are experienced, reduced width membrane (40 to 60 percent of the field sheet width) is installed to reduce the fastener and seam loading.

The roofing membrane may also be fully adhered to an insulation or deck material using an adhesive. Insulation is typically secured to the deck with mechanical fasteners and the TPO roofing membrane is adhered to the insulation.

This type of roof system is highly resistant to wind and its associated uplift forces. Since the sheet is 100 percent affixed to the substrate, the membrane does not flutter due to associated wind forces. With no sheet movement due to the 100 percent attachment of the membrane, the fully adhered roof system is ideal for very visible roofs such as domes or other high slope roofing applications.

Weld-ability
One of the primary benefits of TPO membrane roofing is the ability to fuse the sheets together with a hot air weld. The welding process results in a bond that is actually stronger than the sheet itself. Roof flashing details, such as exhaust vents, pipes and parapet corners are also completed using hot air welds and flashing material (typically non-reinforced).

When properly compounded, TPO membrane has a wide window of weld-ability, allowing the roofing applicator to complete hot air welds consistently in a broad temperature range. Since weld integrity is critical to the performance of the roofing system, it is imperative that the membrane welds properly in a wide range of ambient temperatures. TPO membrane can be welded at speeds up to 80 mm/s (16 ft/min) using a self-propelled hot-air welder, however, optimum welding speeds are 60 to 70 mm/s (12 to 14 ft/min) with the air temperature at the welding nozzle at approximately 540º C (1000º F). TPO is a thermoplastic material and does not “cure” on the rooftop once installed. This allows the sheet to be repaired with proper surface preparation after rooftop exposure.

Wide Sheet Technology
Another benefit that TPO membranes bring are wide width sheets. Currently, TPO membrane is available in the market in widths up to 3.66 m (12 ft). These wider sheets provide installed cost savings by reducing the total number of seams to be completed in the field and the labour associated with the seaming/welding process. Wider sheets also require fewer fasteners and plates for membrane to be secured, fewer rolls for the roofing applicator to handle on the roof, and less membrane being utilized in the seam overlaps.

Recyclability
TPO membrane, reinforced and non-reinforced, is 100 percent recyclable during the production process. During production, if the need arises, the membrane can be ground into “rework” and this regrind can be incorporated into the bottom ply during the extrusion process to produce new TPO product. This process results in 100 percent reuse of recycled product.

Reflectivity
Another important characteristic of TPO membrane is its high level of reflectivity. Because of this, white TPO membranes can meet and even substantially exceed ENERGY STAR performance levels. While TPO membranes typically display reflectivity ratings in the high 80 percent range when new (ENERGY STAR specifications require 65 percent minimum) and in the low 80 percent range after three-year rooftop exposure with cleaning (ENERGY STAR specifications require 50 percent minimum). TPO membranes are highly resistant to mold and algae growth, which can degrade the overall reflectivity of the roof and reduce anticipated energy savings.

Conclusion
Over the past decade, TPO membranes have succeeded in gaining strong roofing industry credibility based on their physical property characteristics, wide sheet technology and long-term rooftop performance throughout the world. The newly approved ASTM TPO specification adds credibility by providing definitive guidelines for minimum membrane properties, thus helping to ensure product quality, durability and longevity. [ source: ASTM Standards for TPO Roofing Membranes ]


2c. PVC Flat Roofing
Durability
PVC is amongst the most durable roofing and waterproofing options as proven through more than 45 years of service on roofs all over the world. Products that serve their intended purpose for a longer period of time without need for replacement are naturally more sustainable.

Recycling
PVC has an established end-of-life roof recycling program that converts the old membrane back into roofing membrane products.

Fire Safety
It is naturally fire retardant and will self extinguish with the removal of the flame source.

Energy Efficiency
Reflective vinyl roofs save energy by reducing the absorption of solar energy and transfer to the building interior. Less heat transferred to the interior means less energy needed for air conditioning. Cooler roofs also minimize the degradation of insulation thermal efficiency that can occur at high roof envelope high temperatures. Vinyl roofing products were the first roofing products to be labelled under the EPA's EnergyStar® Roof Products Program that could also demonstrate 30 years (circa 1999) of demonstrated performance history. According to the EPA, white vinyl roofs may lower air conditioning utility expenses by as much as 50 % in some climates.

Resource Efficiency
Just 47% of the PVC resin's raw materials are derived from petroleum, less than any other single ply roofing membrane. The remaining 53% are derived from salt. Decreasing the United States dependence on foreign oil is universally accepted as a national Security and domestic policy prerogative. Vinyl roofing membranes are the most resource efficient roofing products because of their limited reliance on the hydrocarbon chain/petroleum.

Health & Safety
PVC roofing is inert and contains no dioxins. The plasticizers are highly stable and an integral part of the membrane. They have never been shown by any government body to be harmful to humans.

Code Compliance
PVC meets all applicable building codes. PVC roofing membranes also meet the cool roofing requirements of EnergyStar®, Green Globes™, and LEED®.

Air Quality/Green House Gases
Reflective roofs help to reduce the ambient air temperature in urban areas by decreasing the square footage of dark surfaces. As a result, they in turn help to decrease the formation of smog related pollutants that form when carbon monoxide interacts with warmer ambient air temperatures. Each square foot of dark coloured roof membrane replaced with a reflective PVC roof membrane reduces green house gas emissions. On average, vinyl membranes are carbon neutral after 1.7 years.

Water Quality
PVC roofing membrane is inert and does not contribute any chemicals of concern to storm water runoff.

[source: sarka sonifil]

3. Modified Bitumen Flat Roofing
These roofing membranes are asphalt-based materials, but plasticizers have been added to improve strength, flexibility, water-resistance, etc. They can be incorporated into a conventional BUR roof, or applied as a single-ply membrane. Close cousin of the Built-up-Roof (BUR). Engineered modified bitumen roofing membranes originated in Europe in the mid 1960's and have become a standard application - used successfully in the United States and Canada since approximately 1975.

Increased resistance to brittleness at cold temperatures, greater flow resistance at high temperatures, and increased elasticity can be achieved by blending synthetic rubberized polymers with asphalt in lieu of modification by the blowing process used for BUR asphalt.

There are numerous roof surfacing options for this system which include a factory applied mineral surface, gravel surface, including “cool roof” coatings which are highly-reflective to save on building cooling costs. Mineral-surfaced roofing products are typically furnished with white granules, but are also available in designer colors to match asphalt roof shingles or to otherwise compliment the over all building design.

It gives system designers and roof installers an even broader array of options than BUR roofing. It may be installed by the roofing torch-application method, or “hot-mopped” on the roof like BUR roofing, or applied to the roof with “cold-process” adhesives.

The latest innovation ro this roofing is the self-adhering sheet. Using special combinations of polymers to modify the underside of the sheet, the rolls are manufactured with a release paper. The roof installer removes the release paper and as the sheet is rolled out, it adheres itself to the roofing substrate. This method eliminates the risks associated with the use of torches, hot asphalt, and is completely free of VOC (volatile organic chemicals) fumes during and after roof application.

Benefits of Modified Bitumen Roofing
Proven track record of performance. Superior waterproofing characteristics. Broad range of roof application methods. Wide choice of roof top-surfacing, including “Cool Roofing” options. With insulation, provides an even better-performing building component. High tensile-strength. Available as part of a fire, wind, and/or hail rated roofing system. Competitive roof life-cycle cost. Available with flame-free and VOC-free roof installation. Long-term roof manufacturer warranties are available.