Commercial

Commercial Roofing

There are four main types of flat roofing solutions. They are: Single Ply: PVC, EPDM, TPO, 2 Ply Modified Bitumen systems, 3 Ply (not very common), 4 Ply Build-up Roof (BUR)

• Coal-Tar Pitch Built Up Roof* - Coal Tar is an aromatic hydrocarbon and a by-product from the coking process of the coal industry. It is historically in abundance where coal is used in steel manufacturing. It ages very slowly through volatilization and is an excellent waterproofing and oil resistant product. Roofs are manufactured by heating the coal tar and applying between layers of coal tar saturated felts. It has limitations to application on dead level or flat roofs with slopes less than 1/4 in 12. It has a tendancy to soften in warm temperatures and "heal" itself. It is always ballasted with gravel to provide a walking surface. Coal Tar provides an extremely long life cycle that is sustainable and renewable. It takes energy to manufacturer and to construct a roof with it but it's proven longevity with periodic maintenance provides service for many years, with ages from 50 to 70 years not uncommon, with some now performing for over a century.
• Coal Tar fumes are hazardous and provisions must be made during application to prevent odor from getting into the building. Workers may get higher compensation (Pitch Pay) for having to deal with the health risks. Coal Tar Pitch is also a known carcinogen and excessive and long-term exposure should be avoided.
• Coal tar pitch is often confused with asphalt, and asphalt with coal tar pitch. Although they are both black and both are melted in a kettle when used in roofing, that is where the similarity stops.
• Asphalt Built Up Roof - Asphalt is an aliphatic compound and in almost all cases a byproduct of the oil industry. Some asphalt is manufactured from oil as the intended purpose, and this is limited to high quality asphalt produced for longer lasting asphalt built-up roofs. Asphalt ages through photo-oxidation accelerated by heat. As it ages, the asphalts melt point rises and there is a loss of plasticizers. As mass is lost, the asphalt shrinks and forms a surface similar to alligator skin. Asphalt breaks down slowly in water, and the more exposure the more rapid the degradation. Asphalt also dissolves readily when exposed to oils and some solvents.
• There are four types of roofing asphalt. Each type is created by heating and blowing with oxygen. The longer the process the higher the melt-point of the asphalt. Therefore, Type I asphalt has characteristics closest to coal tar and can only be used on dead level surfaces. Type II, is considered flat and can be applied to surfaces up to 1/4 in 12 slopes. Type III, is considered to be "steep" asphalt but is limited to slopes up to 2 in 12, and Type IV is "special steep". The drawback is, the longer it is processed, the shorter the life. Dead level roofs where Type I asphalt was used as the flood and gravel adhesive has performed nearly as well as Coal Tar.

Asphalt roofs are also sustainable by restoring the lifecycle by making repairs and recoating with compatible products. The process can be repeated as necessary at a significant cost savings with very little impact on the environment.

• Asphalt BUR is the most common type of flat roof at this time. It is made up of multiple layers of reinforcing plies and asphalt forming a redundancy of water proofing layers. The reflectivity of built up roofs depend on the surfacing material used. Gravel is the most common and they are referred to as asphalt and gravel roofs. Asphalt degradation is a growing concern. UV-rays oxidize the surface of the asphalt and produces a chalk-like residue. As plasticizers leach out of the asphalt, asphalt built up roofs becomes brittle. Cracking and alligatoring inevitably follows, allowing water to penetrate the system causing blisters, cracks and leaks. Compared to other systems, installation of asphalt roofs is energy-intensive (hot processes typically use LP gas as the heat source), and contributes to atmospheric air pollution (toxic, and green-house gases are lost from the asphalt during installation).
• Turbo Seal - Self healing gel like membrane that never cures. Made of 45% recycled tire rubber, it goes on top of existing tar (asphalt) roofs then capped with a sheet membrane.
• CSPE - Chlorosulfonated Polyethylene is a synthetic rubber roof. It is more popularly known as Hypalon. This product is usually reinforced and depending upon manufacturer, seams can be heat welded or adhered with a solvent based adhesive.
• EPDM - Ethylene Propylene Diene Monomer is a synthetic rubber most commonly used in single-ply roofing because it is readily available and relatively simple to apply. Problems associated with EPDM include moisture gain under the membrane by vapor drive (occurring on roofs with air conditioned space beneath). Another problem is that EPDM does not like to adhere to itself and seam problems have plagued the industry since inception.

It is a low cost membrane, but when properly applied in appropriate places, it has a life-cyle of 15 to 25 years. Typically, there are three installation methods. Ballasted at 1000 lbs/100 sq.ft. with large round stones. Mechanically attached is another method and is suitable in some applications where wind velocities are not usually high. Fully adhered is the most expensive installation method but proves to give the longest performance of the three methods on roofs with very good drainage and no standing water.

• Modified Bitumen A bitumen is a term applied to both coal tar pitch and asphalt products. Modified Bitumens were developed in Europe in the 1970's when Europeans became concerned with the lower performance standards of roofing asphalt. Modifiers were added to replace the plasticizers that had been removed by advanced methods in the distillation process. The two most common modifiers are APP (attactic polypropylene) from Italy and SBS (styrene-butadiene-styrene)from France. The United States started developing modified bitumen compounds in the late 1970's and early 1980's.

APP was added to asphalt to enhance aging characteristics and was applied to polyester, fiberglass, or polyester and fiberglass membranes to form a sheet good, cut in manageable lengths for handling. Usually applied by heating up the underside of the roll with a torch provided a significant fire hazard and was outlawed in some municipalities when buildings caught fire and some burnt to the ground. Another problem developed when a lack of standards allowed some manufacturers to produce goods with amounts of APP insufficient to enhance the aging characteristics. SBS is used as a modifier for enhancing substandard asphalt and provides a degree of flexibility much like rubber. It also is applied to a myriad of carriers and produced as a sheet-good in rolls that can be easily handled.

• Cold applied liquid membranes - An increasingly popular choice for new roofs and roof refurbishment. No open flames or other heat sources are needed and the glassfibre reinforced systems provide seamless waterproofing around roof protrusions and details. Systems are based on flexible thermoset resin systems such as polyester and polyurethane.
• PVC - Polyvinyl Choride
• TPO - Thermoplastic Polyolefin
• Curon - Cold-curing glass-reinforced polymer composite.
• IB Roof - IB is simply one manufacturer of Seamless modern membrane roof systems. Others include Carlise,Firestone, GAF, JohnsManville,etc. Warranty terms and pricing all differ yet none has been empirically proven to outperform the other, since most applications of the different competing technologies have yet to complete lifecycles. Singly Ply Thermoplastic roof systems are relatively recent and changing technologies. PVC and TPO membranes are taking over the thermosplastic roof market, replacing the EPDM roof system. PVC membranes are shown to be more stable because the chemical formula used to create it is more defined and specific than that of the multi-olefin formulas used to make different TPO membranes. However, TPO has its advantages. Being more like rubber than plastic, it tends to withstand UV rays and thermal shock better than plastic like PVC's. PVC is the more expensive product.

Single Ply EPDM Roof

EPDM: Ethylene Propylene Diene Monomer (or Terpolymer which is simply a product consisting of three distinct monomers). EPDM is classified as a Thermoset material which means it is either fully-cured prior to being installed or that it cures during natural weathering after installation. EPDM roofs are single-ply membranes meaning there is only one ply of roofing material, not multiple plies laminated together. 

EPDM has been in use on roofs in the USA since the 1960's and is one of the most common types of low-slope roofing materials. This is because it is relatively inexpensive, simple to install, and fairly clean to work with when compared to conventional built-up roofs. There aren't the odors and fumes that accompany built-up roofs which appeals to many property owners and managers.

EPDM is a rubber material whose principal components consist of the compounds ethylene and propylene. A flexible rubber matrix forms when a small amount of diene is added to the mix. EPDM is available reinforced or unreinforced with both commonly used; it's also available in either a cured (vulcanized) or uncured (non-vulcanized) state. Vulcanized EPDM is the most common with non-vulcanized often used for flashing purposes.  

EPDM membrane thickness ranges from thirty mils (0.030") to one-hundred mils (0.100") with the most common thicknesses being forty-five mils (0.045") and sixty mils (0.060"). There are three standard application procedures: (1) fully-adhered; (2) mechanically-fastened; (3) loose-laid.   Fully-adhered EPDM uses water or solvent-based adhesives to adhere the rubber to the substrate. Mechanically-fastened EPDM is attached by manufacturer-approved mechanical means to the substrate, and loose-laid membranes are secured only at the perimeters and any penetrations. A ballast of round river rock or concrete pavers is used to hold the materials in place. River rock is usually installed at a rate of 1000 - 1200 pounds per roof square (100 square feet) and the pavers generally weigh approximately 20 pounds per square foot. Structural integrity is important with loose-laid roof systems. The seams of all systems are then sealed using either an adhesive or a splice tape. Splice tapes have tested with a higher tear-strength.

How Long Do They Last?
As with most roofs, EPDM rubber roofs have varying lifespans that depend on numerous criteria. These include environmental conditions such as what type of building (factory or church), how much foot traffic the roof gets, how much water remains on the roof after a rain, and how long it take that water to evaporate. Not to mention geographical location. Roofs in mild climates will outlast roofs in harsher climates. Of course, one of the most important factors in a roof's life expectancy is quality of workmanship. If the roof is not properly installed, then its lifespan will be shortened.

Properly install EPDM rubber roofs should last between 12 and 25 years. Here's a brief breakdown base on observations over the past 15 years::

• 45 Mil Ballasted EPDM Rubber properly installed that drains well - 12 years
• 45 Mil Mechanically Attached roof properly installed that drains well - 12 years
• 45 Mil Adhered roof properly installed that drains well - 12+ years
• 60 Mil Ballasted EPDM Rubber properly installed that drains well - 12+ years
• 60 Mil Mechanically Attached roof properly installed that drains well - 15 years
• 60 Mil Adhered roof properly installed that drains well - 15+ years
• 80+ Mil Mechanically Attached roof properly installed that drains well - 20+ years
• 80+ Mil Adhered roof properly installed that drains well - 20+ years
• 80+ Mil Fleeceback Adhered roof properly installed that drains well - 25+ years

Single Ply PVC Roof

Synthetic roofing and waterproofing materials, generally known as single-ply membranes, were introduced in Canada in the early sixties as an alternative to conventional built-up roofing (BUR). In recent years, they have become viable alternatives because of the rising cost of
labour and petroleum-based bituminous materials, the improvement in polymeric materials, and the need for pliable and easily adaptable membranes for unusual roof configurations.

2 Ply Modified Bitumen Systems

Modified Bitumen (MB) is asphalt that has had modifiers added to it to give it plastic or rubber-like properties. The most common types of modifiers being used are APP (Atactic Polypropylene) and SBS (Styrene Butadiene Styrene).

Rolls of modified bitumen membrane come in widths of 36" (0.9 m) to approximately 39" (1 m) and cover an area of approximately 100 square feet to 112 square feet per roll. Surfacings for these roll materials consist of a smooth surface, or mineral granules, aluminum, copper, or an aggregate such as gravel or slag that is set it hot asphalt.

4 Ply Build-Up Roof (BUR):

Built-Up Roof: a roof consisting of multiple plies of roof felts laminated together with bitumen. Built-up roof material can consist of bitumen-saturated felt, coated felt, polyester felt or other fabrics. A surfacing is generally applied and can be asphalt, aggregate (gravel or slag), emulsion or a granule-surfaced cap sheet.

This section was written simply to give people an idea of what a Built-Up Roof (B.U.R. for short) is and how it’s put together. The materials and information listed here are not comprehensive nor do they represent all types of built-up roof materials available.

Built-Up Roofing is one of the oldest and most reliable ways of installing a new roof. It was first known as composition roofing and started in the 1840's. B.U.R.’s come in two basic types, asphalt and coal tar, and three basic components – (1) the waterproofing component, (2) the reinforcing component, and (3) the surfacing component which is used to protect the other components from the elements.

There are many different types of materials used in Built-Up Roofing. Some of these are:

Other items not listed are flashing materials, mastics, caulking material, fasteners, and roof insulation, to name a few.

Now that you see the wide variety of materials available, you are probably wondering what the differences are. The difference in the base sheets is simple. Venting base sheets are specially-designed for use with moisture-cured substrates such as light weight insulating concrete or poured gypsum. Neither of which you homeowners will have to worry about. Regular base sheets are generally used with nailable decks such as plywood. The differences in the felts are determined by the types of reinforcement materials used. For instance, polyester felts are stronger than fiber glass felts which are stronger than organic felts. The fiber glass felts will vary among themselves in quality with Type III being the lowest quality and Type VI being the highest.

Gravel or slag surfacings are probably the most popular. The next most popular surfacings are probably the granule-surfaced cap sheets, commonly called 90 pound because they used to weigh approximately that much per square. Now they weigh around 72 pounds per square. Then come the emulsions which can be spray, brush, or roller applied.

Now we’ll talk about how B.U.R.’s are put together. Base sheets are usually the first piece of Built-Up Roofing material installed and are usually mechanically-fastened (nailed) to the deck or substrate. Then come the felts. These can be installed with either hot asphalt or coal tar, or cold-applied liquid adhesive, a.k.a. solvent-based asphalt or "cutback" asphalt. Approximately twenty-five to thirty pounds of hot asphalt or twenty to twenty-five pounds of coal tar per 100 square feet (roof square) is used between each ply. Three to five gallons of the cold-applied adhesive is used per square. Last is the surfacing. With a cap sheet, the same amount of bitumen or lap cement is used to install the cap sheet as is used to install the plies. With gravel or slag, a flood coat of about sixty pounds per square of asphalt or seventy pounds per square of coal tar is applied and 400 – 500 pounds per square of gravel or 300 – 400 pounds per square of slag is embedded. Emulsion surfacings will vary. Usually it’s around three gallons per square that is used. If emulsion is what is preferred, an aluminum reflective coating should be applied after the emulsion cures to help reflect damaging UV rays.

Built-up roofs can be installed over just about any type of roof deck as long as the proper substrate is used. BUR's can't be mopped to a wood roof deck. In this case a rosin sheet and base sheet are needed first. With steel roof decks, the thickness of the deck should be a minimum of 22 gauge and some type of approved insulation should be mechanically-attached to the deck to provide a substrate. Manufacturers should be consulted before mopping to Polyisocyanurate ("iso" for short) insulation. Many manufacturers will not warrant a roof if the felts are mopped directly to the iso and a coverboard such as wood fiber or perlite is needed. In some cases adhesives are being used to attach the insulation to the deck but be sure the roofing materials manufacturer is consulted before this is done. With structural concrete roof decks, the roof is often mopped directly to the deck after it's cleaned. Sometimes a thermal insulation is used to provide a substrate. Thermal insulation can be attached by mechanical means, adhesives, or even hot-mopped. If the insulation is hot-mopped with bitumen, then care needs to be taken so as not to allow the bitumen access to the interior of the building at joints in the roof deck. Also, if Isocyanurate insulation is used, only 4' X 4' sheets can be mopped due to its propensity to warp and curl. With lightweight insulating concrete, pre-cast gypsum panels, or poured gypsum, venting base sheets are attached with special fasteners and then insulation may or may not be installed over the base sheet and then the roof membrane installed. In some cases a vapor barrier will be necessary. Built-up roofs cannot be mopped directly to lighweight insulation or gypsum. Cement fiber roof decks should have a base sheet or insulation mechanically-attached to it before installing the roof. Insulation should be installed in two layers with all joints offset and staggered a minimum of twelve inches.

How Long Do They Last?
The service life of a roof is dependent on many factors: geographical location & weather conditions, foot traffic, materials used, conditions under which the roof was installed, slope of roof, type of surfacing material, etc. Under ideal conditions, a 3-ply built-up roof should last at least fifteen years, a 4-ply should last at least 20 years, and a 5-ply should last at least 25 years. This author has seen ten year old 4-ply roof that needed to be replaced and twenty year old 3-ply roofs that were still functioning.