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Bituminous waterproofing systems are designed to protect residential and commercial buildings. Bitumen (asphalt or coal-tar pitch) is a material made up of organic liquids that are highly sticky, viscous, and waterproof. [1] Systems incorporating bituminous-based substrates are sometimes used to construct roofs, in the form of "roofing felt" or "roll roofing" products.
Roofing felt (similar to and often confused with tar paper, but historically made from recycled rags rather than heavy kraft paper) has been used for decades as waterproof coverings in residential and commercial roofs as an underlay(ment) (sarking) beneath other building materials, particularly roofing and siding materials, and is one type of membrane used in asphalt built up roofing (BUR) systems. Over time the felt's natural mesh used as a substrate for asphalt impregnation (derived from fabrics like cotton or burlap) has evolved into synthetic products performing the same function with improved durability. Other changes with time have enhanced performance, with roofing felt remaining a heavier and more durable product than tar paper.
The rapid application of waterproof or water-resistant roofing underlay protects the roof deck during construction until the roofing material is applied and is required for roofs required to meet Underwriters Laboratory (UL) fire ratings. The separation of the roof covering from the roof deck protects the roof covering from resins in some sheathing materials and cushions unevenness and old nails and splinters in re-roofing applications. The underlayment also sheds any water which penetrates the roof covering from an ordinary leak, a leak from wind-driven rain or snow, wind damage to the roof covering, or ice dams. However, the application of underlays may increase the roof temperature, which is the leading cause of ageing of asphalt shingles. Not installing an underlay may void the roof covering warranty.[ citation needed ]
Felt paper is available in several grades, the most common being Type 1—commonly called 15-pound (15#) or No. 15 (#15)—and Type 2—commonly called 30-pound (30#) or No. 30 (#30). The weight designations originated with organic base felt weighing 15 or 30 pounds per 100 sq. ft. (6.8 kg or 14 kg per 9.3 m2). However, modern base felts are made of lighter-weight fibre, so the weight designations, though common colloquially, are no longer literally accurate. [2] A heavier class of materials with a similar construction but designed for civil engineering, environmental protection, and mining applications are known as Bituminous Geomembranes (BGMs). BGMs are distinguished in part by larger roll widths which can exceed 5m and substantial thickness of up to 6.0mm. [3]
Another basic designation is organic or inorganic. Organic felt paper has a base material made with formerly living materials such as rag fibre, hessian (burlap), or cellulose fibres (wood, or jute). Organic felt papers are now considered obsolete, having dwindled to just five percent of the market by 1987. [4] Inorganic base products are polyester, glass fibre developed in the 1950s, and historically, asbestos mat. Polyester mat is weaker and less chemically stable than fibreglass but because it is cheap is gaining market share. Polyester mat is primarily used with the more flexible modified-bitumen felt products. Asbestos mat was the first inorganic base material but was outlawed in the 1980s for health reasons but is still in use on some buildings. Inorganic felts are lighter, more tear-resistant, more fire-resistant, and do not absorb water. Another type of felt paper is perforated for use in built-up roofing and is not for use as a water-resistant underlay.
Heavier material is typically used for underlayment of longer-lived roof materials in order to match their longer life span, and on less sloped roofs, which are more susceptible to leaking. For example, two layers of No. 30 felt might be used under a slate or tile roof, whereas a single layer of No. 15 might be adequate for a steeply raked roof of 24-year asphalt shingles. [5] s0
Roofing felt is manufactured in roll format. Rolls of base felt are pulled on rollers through large tanks of bitumen mixes until they are saturated with the tar-like bitumen mixture, producing rolls of water-resistant but breathable material.
Modified bitumen is mixed with filler components such as limestone, sand, or polymers such as atactic polypropylene (APP) that gives rigidity and tear resistance or styrene-butadiene styrene (SBS), a rubber additive that gives more elastic benefits. [6]
The American Society for Testing Materials (ASTM) standards that apply to felt paper are:
The Canadian Standards Association standards are:
Roll roofing is a bitumen product similar to asphalt shingles meant for direct exposure to the weather. To protect its asphaltic base from ultraviolet degradation mineral granules are added on top of the felt, also decreasing the product's fire vulnerability. Thin, removable transparent film is added to the base of rolled roofing during manufacturing on all torch-on products. This stops the felt from sticking to the mineral layer when rolled up during the packaging process. A similar removable membrane on self-adhesive rolled roofing separates the adhesive from the mineral layer. Torch-on roofing felt also receives a removable membrane to keep it from sticking to itself prior to application. [12]
The complex chemical composition of bitumen makes it difficult to identify the specific component(s) responsible for adverse health effects observed in exposed workers. Known carcinogens have been found in bitumen fumes generated at work sites. Observations of acute irritation in workers from airborne and dermal exposures to fumes and aerosols and the potential for chronic health effects, including cancer, warrant continued diligence in the control of exposures.
From 1905 to 1988, The Paraffine Paint Co. of San Francisco had Malthoid as a trademark for waterproof and weatherproof building and roofing materials made of paper and felt in whole or in part. [14] However, it had become well known before that. [15] About 1913, Paraffine promoted its Malthoid roofing materials with a 16-page booklet. [16] In 1941, the Duroid Company began making Malthoid in Onehunga, New Zealand. [17]
Malthoid was once common enough to be used as a generic description of flat roofing material in New Zealand and South Africa (item 26). A description of a New Zealand house built about 1914 says it was, "built of timber framework. covered by sheets of asbestos. The roof was closely timbered, then covered by strips of Malthoid paper. This was then painted with tar and topped off with a sprinkling of sand." [18] Railway vehicles in Australia were roofed with Malthoid. [19] Malthoid is still available for flat roofs and damp courses. [20]
Bitumen is an immensely viscous constituent of petroleum. Depending on its exact composition it can be a sticky, black liquid or an apparently solid mass that behaves as a liquid over very large time scales. In American English, the material is commonly referred to as asphalt. Whether found in natural deposits or refined from petroleum, the substance is classed as a pitch. Prior to the 20th century the term asphaltum was in general use. The word derives from the ancient Greek ἄσφαλτος ásphaltos, which referred to natural bitumen or pitch. The largest natural deposit of bitumen in the world is the Pitch Lake of southwest Trinidad, which is estimated to contain 10 million tons.
A roof is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of temperature, and wind. A roof is part of the building envelope.
Building material is material used for construction. Many naturally occurring substances, such as clay, rocks, sand, wood, and even twigs and leaves, have been used to construct buildings and other structures, like bridges. Apart from naturally occurring materials, many man-made products are in use, some more and some less synthetic. The manufacturing of building materials is an established industry in many countries and the use of these materials is typically segmented into specific specialty trades, such as carpentry, insulation, plumbing, and roofing work. They provide the make-up of habitats and structures including homes.
Tar paper is a heavy-duty paper used in construction. Tar paper is made by impregnating paper with tar, producing a waterproof material useful for roof construction. Tar paper is similar to roofing felt, historically a felt-like fabric made from recycled rags impregnated with melted asphalt, and today evolving into a more complex underlayment of synthetic mesh or fiberglass strands waterproofed by synthetically enhanced asphalt.
EPDM rubber is a type of synthetic rubber that is used in many applications.
A flat roof is a roof which is almost level in contrast to the many types of sloped roofs. The slope of a roof is properly known as its pitch and flat roofs have up to approximately 10°. Flat roofs are an ancient form mostly used in arid climates and allow the roof space to be used as a living space or a living roof. Flat roofs, or "low-slope" roofs, are also commonly found on commercial buildings throughout the world. The U.S.-based National Roofing Contractors Association defines a low-slope roof as having a slope of 3 in 12 (1:4) or less.
Tar is a dark brown or black viscous liquid of hydrocarbons and free carbon, obtained from a wide variety of organic materials through destructive distillation. Tar can be produced from coal, wood, petroleum, or peat.
Underlay may refer to flooring or roofing materials, bed padding, or a musical notation.
Waterproofing is the process of making an object, person or structure waterproof or water-resistant so that it remains relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environments or underwater to specified depths.
Roof shingles are a roof covering consisting of individual overlapping elements. These elements are typically flat, rectangular shapes laid in courses from the bottom edge of the roof up, with each successive course overlapping the joints below. Shingles are held by the roof rafters and are made of various materials such as wood, slate, flagstone, metal, plastic, and composite materials such as fibre cement and asphalt shingles. Ceramic roof tiles, which still dominate in Europe and some parts of Asia, are still usually called tiles. Roof shingles may deteriorate faster and need to repel more water than wall shingles. They are a very common roofing material in the United States.
Domestic roof construction is the framing and roof covering which is found on most detached houses in cold and temperate climates. Such roofs are built with mostly timber, take a number of different shapes, and are covered with a variety of materials.
An asphalt shingle is a type of wall or roof shingle that uses asphalt for waterproofing. It is one of the most widely used roofing covers in North America because it has a relatively inexpensive up-front cost and is fairly simple to install.
Chipseal is a pavement surface treatment that combines one or more layer(s) of asphalt with one or more layer(s) of fine aggregate. In the United States, chipseals are typically used on rural roads carrying lower traffic volumes, and the process is often referred to as asphaltic surface treatment. This type of surface has a variety of other names including tar-seal or tarseal, tar and chip, sprayed sealsurface dressing, or simply seal.
Damp proofing in construction is a type of moisture control applied to building walls and floors to prevent moisture from passing into the interior spaces. Dampness problems are among the most frequent problems encountered in residences.
A roof coating is a monolithic, fully adhered, fluid applied roofing membrane. Many roof coatings are elastomeric, that is, they have elastic properties that allow them to stretch and return to their original shape without damage.
Underlayment may refer to:
Asphalt roll roofing or membrane is a roofing material commonly used for buildings that feature a low sloped roof pitch in North America. The material is based on the same materials used in asphalt shingles; an organic felt or fiberglass mat, saturated with asphalt, and faced with granular stone aggregate.
Bituminous Geomembrane (BGM) is a type of geomembrane consisting of a reinforcing geotextile to provide mechanical strength and elastomeric bitumen to provide impermeability. Other components such as sand, a glass fleece, and/or a polyester film can be incorporated into the layers of a BGM. Bituminous geomembranes are differentiated from bituminous waterproofing materials used in buildings due in part to their wide roll width, which can exceed 5m, and their substantial thickness of up to 6.0mm.
In construction, covering is the exterior layer of a building's roof. The covering ensures waterproofing by directing and collecting rainwater. It also provides mechanical protection against various external elements such as dust and intrusions. Additionally, it must withstand static mechanical pressures from snow and dynamic forces from strong winds.
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