Glossary

Glossary of Roofing Terms


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Absorptivity:
Each surface has a default emissivity and solar absorptivity. The solar absorptivity is the fraction of incoming solar energy that the surface absorbs. The absorptivity can be calculated by integrating the product of the spectral solar radiance striking the surface by the spectral emissivity (or 1.0-reflectance) of the surface. The absorptivity property determines the amount of incident solar energy absorbed.
Accelerator:
Any material added to stucco, plaster or mortar which speeds up the natural set.
Aggregate:
A surfacing material or ballast for a roof system. Aggregate can be rock, stone, crushed stone or slag, water-worn gravel, crushed lava rock or marble chips.
Above-Grade:
The portion of a building that is above ground level.
Adhere:
to cause two surfaces to be held together by adhesion, typically with asphalt or roofing cements in built-up roofing and with contact cements in some single-ply membranes.
Adhesion:
The property of a coating or sealant to bond to the surface to which it is applied.
Adhesive Failure:
Loss of bond of a coating or sealant from the surface to which it is applied.
AIA:
American Institute of Architects.  Sealoflex is approved by the AIA as a registered provider. Contact your representative for class information. 
Alignment Notch:
A cutout projection or slit on the sides or ends of shingles that act as guides in application to secure proper exposure.
Alligatoring:
A condition of paint or aged asphalt brought about by the loss of volatile oils and the oxidation caused by solar radiation. "Alligatoring" produces a pattern of cracks resembling an alligator hide and is ultimately the result of the limited tolerance of paint or asphalt to thermal expansion or contraction.
Ambient Temperature:
The temperature of the air.
ANSI:
American National Standards Institute
APP (Atactic Polypropylene) Modified:
Asphalt based raw roofing, usually torch-applied.
Application Rate:
the quantity (volume or thickness) of material applied per unit area.
Asphalt:
A bituminous compound, dark brown or black in color, used in the manufacture of asphalt roofing shingles.
Asphalt shingle:
a shingle manufactured by coating a reinforcing material (felt or fibrous glass mat) with asphalt and having mineral granules on the side exposed to the weather.
Assembly Number:
A unique number assigned to each RoofNav (FM Approval software tool) assembly. A valid assembly number consists of three numbers separated by hyphens. The number of digits in each section may vary.
ASTM:
American Society for Testing and Materials. A voluntary organization concerned with development of consensus standards, testing procedures and specifications.
Attic:
The space immediately under the sloping roof of a house.
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Back surfacing:
Fine mineral matter applied to the back side of shingles to keep them from sticking.
Ballast:
an anchoring material, such as aggregate or precast concrete pavers, which employs the force of gravity to hold (or assist in holding) single-ply roof membranes in place.
Barrel Roof:
A roof design which in cross section is arched. Consists of a continous arch of semi-circular sections.
Base flashing:
That portion of the flashing attached to or resting on the deck to direct the flow of water onto the roof covering.
Battens:
1"x2"x4' wood strips nailed to the roof, upon which the field tile hangs.
Bead:
An applied sealant in a joint irrespective of the method of application, such as caulking bead, glazing bead, etc.
Below Grade:
The portion of a building that is below ground level.
Bitumen:
Any of various mixtures of hydrocarbons occurring naturally or obtained through the distillation of coal or petroleum.
Blends:
Mixtures of various colored granules found on the one face of mineral-surfaced roofing.
Blind nailing:
Nails driven in such a way that the heads are not visible.
Blister:
An enclosed raised spot evident on the surface of a building. They are mainly caused by the expansion of trapped air, water vapor, moisture or other gases.
Board Stock Insulation:
A board stock insulation has a core of one of the following materials: APA-rated OSB; asphalt/glass; glass-based; gypsum; mineral wool; perlite; polyisocyanurate/polyurethane; expanded polystyrene foam (EPS); extruded polystyrene foam (XPS); or wood fiber. The material, the number of board stock layers, and the position of the product within the assembly determine whether it will be classified as an insulation, a cover board, or a thermal barrier.
Bond breaker
A layer or coating that is applied to a specific area of a substrate, such that, when a subsequent layer or coating is applied over the bond breaker, it will not bond or adhere in that area.
Boston lap:
A method of finishing the ridge of a shingle course, using ovefrlapping vertical joints.
Bowstring roof:
A roof constructed with curved timber trusses and horizontal tie-beams connected by light diagonal lattices of wood.
Built-up roof (BUR):
An outer covering of a comparatively flat roof, consisting of several layers of saturated felt. As laid, each layer is mopped with hot tar or asphalt. The top layer is finished with a mineral or rock covering and a special coating.
Bundle:
A package of shingles. There are 3, 4 or 5 bundles per square.
Butt edge:
The lower edge of the shingle tabs.
Butterfly Roof:
A roof assembly which pitches sharply from either side toward the center.
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Cant Strip:
A triangular-shaped strip of material used to ease the transition from a horizontal plane to a vertical plane. Cant strips can be made of wood, wood fiber, perlite or other materials.
Cantilever:
A projecting beam or other structure supported only at one end.
Cap flashing:
The portion of the flashing that is built into a vertical surface to prevent water seepage behind the base flashing. Cap flashing overlaps the base flashing.
Cap Sheets:
In roofing, one to four plies of felt bonded and top coated with bitumen that is laid over an existing roof as a treatment for defective roofs.
Caulk:
To fill a joint with mastic or asphalt cement to prevent leaks.
CDX Plywood:
CDX plywood is produced by gluing together sheets of veneer, with each layer being glued the opposite grain to the one below it. The result is a wooden sheet that is proportionally as strong as steel, without the weight that comes along with concrete or steel. Because of this strength, CDX plywood is the most popular choice for interior flooring; CDX plywood will stand up to many years of use and abuse without warping or breaking. See CDX Plywood vs OSD (OSB) Plywood.
Cement:
A substance which, by curing between the two surfaces to which it has been adhered, binds them together.
Ceramic Granules:
Roofing granules in which color is fused to rock under extreme heat to provide a long lasting finish.
CEU (Continuing Education Unit):
A Continuing Education Unit is a unit of study awarded to a student for attending an educational course in the field of study associated with the student's trade, or field of work. CEUs in relation to real time vary depending on the organization/affiliation for whom the student is seeking CEUs. Sealoflex is authorized to provide CEUs for: the AIA (American Institute of Architects), Dade County (Florida), the Florida Contractors Licensing Board (CILB) and RCI. Refer to the section on Trainings.
Chalk line:
A line made on the roof by snapping a taut string or cord dusted with chalk. Used for alignment purposes.
Chicken ladder:
Hooks over the ridge by means of broad 2x4s nailed to the top, to provide safe footing on steep pitches.
Chimney
Masonry or brick work containing one or more flues, projecting through and above the roof.
Cistern:
A receptacle for holding water or other liquid, especially a tank for catching and storing water. The walls of a cistern must be watertight in order to retain moisture.  
Class "A":
The highest fire-resistance rating for roofing as per ASTM E-108. Indicates roofing is able to withstand severe exposure to fire originating from sources outside the building.
Class "B":
Fire-resistance rating that indicates roofing materials are able to withstand moderate exposure to fire originating from sources outside the building.
Class "C":
Fire-resistance rating that indicates roofing materials are able to withstand light exposure to fire originating from sources outside the building.
Clerestory:
An upward extension of enclosed daylighted space created by carrying a setback vertical, windowed wall up and through the roof slope.
Coating:
A layer of viscous asphalt applied to the base material into which granules or other surfacing is embedded. Alone, not a waterproofing system. Example: Sealoflex Finish Coat or Sealoflex CT Top.
Cohesive Failure:
Internal splitting of a compound resulting from over-stressing of the compound.
Collar:
Pre-formed flange placed over a vent pipe to seal the roof around the vent pipe opening. Also known as a vent sleeve.
Concrete:
A construction material that consists, in its most common form, of Portland Cement, aggregate (usually gravel and sand) and water. Concrete solidifies and hardens after mixing and placement due to a chemical process known as hydration. The water reacts with the cement, which hardens, bonding the other components together and eventually creating a stone-like material.
Condensation:
The change of water from vapor to liquid when warm, moisture-laden air comes in contact with a cold surface.
Cool Roofing
A cool roof is defined as a roof surface that has both high reflectivity and high emissivity. High reflectivity requires the surfacing material to reflect solar energy away from the surface. High emissivity requires radiating heat energy away from the surface. Roofs undergo significant expansion and contraction as they heat and cool throughout the day. Heat absorbed by the roof can also accelerate degradation by ultraviolet rays and water. A reflective roof can reduce the amount of thermal shock that occurs on the roof surface and prolong the life of the roof. See Solar Absorptivity Chart.
Coping:
The covering piece on top of a wall, conventionally covered with metal. A more modern and effective technique is to apply a waterproofing system, such as the Sealoflex System.
Counter flashing:
That portion of the flashing attached to a vertical surface to prevent water from migrating behind the base flashing.
Course:
A row of shingles or roll roofing running the length of the roof.
Coverage:
Amount of weather protection provided by the roofing material. Depends on number of layers of material between the exposed surface of the roofing and the deck; i.e., single coverage, double coverage, etc.  Usually expressed in gallons per square foot.
Crack:
a non-linear separation or fracture occurring in a material. May be generally caused by induced stress, dimensional instability or substrate movement.
Crackbridging:
A characteristic of a coating (e.g., Sealcoat Elastic, Coraflex) which indicates good adhesion and resistance to cracking under stress or pressure.
Cricket:
A peaked saddle construction at the back of a chimney to prevent accumulation of snow and ice and to deflect water around the chimney.
Cured Concrete:
concrete that has attained its intended design performance properties.
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Deck or Decking:
The structural "skin" of a roof over which roofing in applied. Most new homes have decking made of plywood. There are four main types of decking commonly used on residential roofing projects:
Plywood:
Plywood is strong, durable, and light. It comes in many grades with ratings from A to D. Use only exterior grade plywood for decking. The thickness of plywood depends on the spacing of the rafters.
OSB:
Oriented strand board (OSB) is cheaper than plywood, but not as strong as plywood, and does not hold nails as well as plywood. One side has a slip resistant coating and should be placed facing up.
Tongue and groove 2-by-6:
If a roof will be seen from the inside (no ceiling installed), tongue and groove is used. It is a wood decking that provides great insulation without additional rigid roof insulation in moderate climates. Also, the boards can be painted or stained on the inside to match the interior.
Step sheathing:
Step sheathing is used alone or in combinations with solid sheathing for installation of tiles or shakes. Step sheathing allows air circulations under the tiles by using 1-by-6 or 2-by-6 boards that are evenly spaced so that air can move under the tiles or shakes.
Degree Days:
The difference between a reference temperature (usually 65° F, 18.3° C) and the mean temperature for the day, times 24 hours, times the number of days in the period. Degree days are used to compare the severity of cold or heat during the heating or cooling season.
Delamination:
Separation of the laminated layers of a component or system.>
Dimensional shingle:
A shingle that is textured, overlayed, or laminated and designed to produce a three-dimensional effect. Similar to Laminated shingle and Architectural shingle.
Dormer:
A framed window unit that projects through the sloping plane of a roof.
Double coverage:
Application of asphalt roofing such that the lapped portion is at least two inches wider than the exposed portion, resulting in two layers of roofing material over the deck.
Downspout:
A pipe for draining water from roof gutters. A downspout is also called a leader.
Drip Edge:
a metal flashing or other overhanging component, with an outward projecting lower edge, intended to control the direction of dripping water and help protect underlying building components. A drip edge also can be used to break the continuity of contact between the roof perimeter and wall components to help prevent capillary action.
Dry In:
To make a building waterproof.
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Eaves:
The horizontal, lower edge of a sloped roof.
EIFS:
Exterior Insulating Finish System; exterior wall cladding system consisting primarily of polystyrene foam board with a textured acrylic finish that resembles plaster or stucco.
Elastomer:
A natural or synthetic material which, at room temperature, can be stretched under low stress and, upon immediate release of the stress or force, will return quickly to its approximate original dimensions. ("Elast" from "Elastic" and "omer" from "Polymner".)
Elastomeric:
the elastic, rubber-like properties of a material that will stretch when pulled and will return relatively quickly to its original shape when released.
Elongation:
the ability of a material (e.g., roofing membrane) to be stretched by the application of a force.
Energy Star®:
A registered trademark of the U.S. government. The ENERGY STAR® Program* represents a voluntary partnership between the federal government and businesses to promote energy efficiency and environmental activities. ENERGY STAR® labeled roof products are reflective and lower roof surface temperature by up to 100°F., decreasing the amount of heat transferred into a building. ENERGY STAR® labeled roof products are designed to help save money on utility bills and reduce energy waste.  Reflective roof products can help reduce the "heat island effect," a phenomenon in which cities can be 2 to 8°F. warmer than the surrounding countryside. Such heat islands occur, in large part, because many buildings and paved surfaces are designed with dark materials that absorb heat from the sun. This heat is released at night, causing the air temperature to remain high. The resulting elevated temperature leads to an increased demand for air conditioning in buildings, increased fuel use for vehicle air conditioning, increased levels of smog, and associated increased levels of heat-related and smog-related health problems. Installing reflective roofs helps reduce the heat island effect, decreasing the amount of smog in the air and benefiting the entire community.  *ENERGY STAR® is a registered trademark of the U.S. government.
Emissivity:
The measure of a surface’s ability to emit long-wave infrared radiation.
EPDM:
Ethylene Propylene Diene Monomer. A single ply membrane consisting of synthetic rubber; usually 45 or 60 mils. Application can be ballasted, fully adhered or mechanically attached.
EPS Board:
Expanded polystyrene. A very light-weight insulation roofing material with a foam structure.
Expansion Joint:
a structural separation between two building elements that allows free movement between the elements without damage to the roofing or waterproofing system.
Exposure:
Portion of the shingle exposed to the weather. Exposure is measured from the butt of one shingle to the butt of the next.
Extensive (Green Roof):
A Green Roof with plantings such as grasses or small plants.
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Fabric:
a woven cloth or material of organic or inorganic filaments, threads or yarns used for reinforcement in certain membranes and flashings. See Fabric Chart.
Factory Mutual Research Corporation (FMRC):
(commonly referred to as "FM"): a research and testing organization that classifies roofing components and assemblies for their fire, traffic, impact (hail), weathering, and wind-uplift resistance for four major insurance companies in the United States. Their specifications have become industry standards.
Fascia:
Horizontal trim at the eaves that covers the rafter ends.
Fasteners:
any of a wide variety of mechanical devices and assemblies, including nails, screws, cleats, clips, and bolts, which may be used to secure various components of a roof assembly.
Felt:
A flexible sheet that is saturated with asphalt and used as an underlayment, sometimes called "tar paper".
Ferrous
Refers to objects made of or partially made of iron, such as ferrous pipe.
Fiber-cement:
A roofing material that has cellulose (wood fiber) mixed into it. Cellulose absorbs water and can add greatly to the roof's weight, while reducing its longevity.
Fiberglass Insulation:
blanket or rigid board insulation, composed of glass fibers bound together with a binder, faced or unfaced, used to insulate roofs and walls. Rigid boards usually have an asphalt and Kraft paper facer.
Fiberglass Mat:
An asphalt roofing base material made from glass fibers.
Fire Resistance
– The ability of a roof top material to act as a barrier to the spread of fire and confine it to the area of origin. There are established test procedures for external fire exposure to classify roof systems into three classes:  Class A, B, or C.
Fishmouth:
(1) a half-cylindrical or half-conical shaped opening or void in a lapped edge or seam, usually caused by wrinkling or shifting of plysheets during installation.
Flaking:
detachment of a uniform layer of a coating or surface material, usually related to internal movement, lack of adhesion or passage of moisture.
Flame Spread:
Per ASTM E 84, a measure of relative combustibility. The flame spread of a tested material is rated relative to asbestos cement board (flame spread=0) and red oak flooring (flame spread = 100).
Flash Point:
The critical temperature at which a material will ignite.
Flashing:
Pieces of metal or roll roofing used to prevent seepage of water into a building around any intersection or projection in a roof such as vent pipes, chimneys, adjoining walls, dormers and valleys. Galvanized metal flashing should be minimum 26-gauge. There are 4 main types of flashing used in residential roofing systems:
Valley flashing:
This flashing is used in open valleys of the roof. Most often leaks are found in the valley flashings due to flashing that is nailed to tightly to the decking or shingles that are not trimmed far enough off the flashing.
Plumbing vent flashing:
Plumbing vent flashing prevents rainwater from running into holes cut for pipes in the roof. This flashing is sold according to the size of the vent pipe and the roof angle. Roofing material is installed over the flashing.
Lead flashing:
When working with tile roofs, lead flashing is used. In the case of a plumbing vent flashing, the lead flashing is actually molded to the shape of the tile's surface. Then the top of the lead flashing is covered by the next tile to prevent water from seeping under the flashing.
Step flashing:
When a chimney or dormer wall intercepts the slope of the roof, step flashing is used. Step flashing is usually a metal piece that is bent in the middle, so that one end lays on the roof, and the other against the vertical wall of the dormer or chimney.
Flashing is one of the most important elements of the roof because it seals the seams and joints of the roof--the locations where leaks are most likely to occur. Often, flashing is not maintained well, or installed correctly in the first place. Check for the following signs that your flashing needs maintenance or repair:
  • Rusting of metal flashing
  • Excess leaves and debris in valleys or seams of the roof (can lead to rusting and corroding of the metal)
  • Prolonged exposure to the elements such as moisture, UV rays, climate changes--especially when asphalt compounds or caulking material is used. Look for cracks, loss of elasticity and delamination.
In many cases the flashing can be cleaned and then repaired, relaminated or repainted (even in the case of rust). In other cases, the flashing may need to be replaced.
Flashing cement:
An asphalt-based cement used to bond roofing materials. Flashing cement is also known as mastic.
Fluid-Applied Elastomer:
a liquid Elastomeric material that cures after application to form a continuous waterproofing membrane.
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Gable roof:
A type of roof containing sloping planes of the same pitch on each side of the ridge. A gable roof typically contains a gable at each end.
Galvanized Steel:
steel coated with zinc for corrosion resistance.
Gambrel roof:
A type of roof containing two sloping planes of different pitch on each side of the ridge. The lower plane has a steeper slope than the upper. A gambrel roof usually contains a gable at each end, just like a standard gable roof.
Granules:
Ceramic-coated colored crushed rock that is applied to the exposed surface of asphalt roofing products.
Green Roof:
A roof of a building that is partially or completely covered with vegetation and soil, or a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a roof barrier and drainage and irrigation systems. 
Gutter:
The trough that channels water from the eaves to the downspouts.
Gypsum:
Gypsum is the more common name for a mineral compound called calcium sulphate dihydroxide. It is commonly used to manufacture drywall panels.
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Hip:
The inclined external angle formed by the intersection of two sloping roof planes. The hip runs from the ridge to the eaves.
Hip roof:
A type of roof containing sloping planes of the same pitch on each of four sides. A hip roof contains no gables.
Hip shingles:
Shingles used to cover the inclined external angle formed by the intersection of two sloping roof planes.
Hydration:
Mineral hydration is an inorganic chemical reaction where water is added to the crystal structure of a mineral, usually called a hydrate. Hydration is the mechanism by which Portland Cement develops strength.
Hypalon®:
a registered trademark of E.I. DuPont de Nemours, Inc., for a rubber roofing product, "chlorosulfonated polyethylene".
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Ice dam:
Ice dams occur when snow melts near the ridgelines of warm roofs (roofs without adequate ventilation). As the water runs down the roof to the overhang, it cools and freezes. If the snow continues this melt and freeze process, an ice dam can form that can seep under the shingles, through the decking and into the house. This, of course, can cause serious roof leaks--even in freezing temperatures.   The best prevention to ice dams is a well-ventilated (cool) roof. Additional protection for your roof can be applied with an impermeable ice and water membrane. The membrane is installed on top of the decking, under the roofing material. Temporary prevention of ice dams can also be done through the use of electric cables along the eaves of the roof (where the dams usually form). However, new ice dams can form above the cables and still cause extensive damage. Another emergency solution to ice dams is to fill a sock or nylon with calcium chloride. Lay the stocking vertically across the ice dam. The calcium chloride will melt the ice and release the water so that it can drain outside, and not inside your roof.
Intake Ventilation:
The part of a ventilation system used to draw fresh air in. Usually vents installed in the soffit or along the eaves of a building.
Intensive (Green Roof):
A Green Roof with plantings such as trees and large bushes.
ISO Board:
Polyisocyanurate Board-a polyurethane foam supplied in board form primarily as an insulation material for the construction industry.
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Joists:
Any of the small timbers or metal beams ranged parallel from wall to wall in a structure to support a floor or ceiling.
Joule:
The International System unit of electrical, mechanical, and thermal energy. A unit of electrical energy equal to the work done when a current of one ampere is passed through a resistance of one ohm for one second.
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Kynar Coating:
Architectural coating that is UV stable and suitable for exterior use on aluminum and other metal surfaces.
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Laitance:
a layer of weak non-durable material containing cement and fines from aggregates, brought by bleeding water to the top of over wet concrete. Laitance may be detected by scraping the concrete surface with a putty knife; if a quantity of loose powdery material is observed or easily removed, excessive laitance may be considered to be present.
Laminated shingles:
Strip shingles containing more than one layer of tabs to create extra thickness. Laminated shingles are also called three-dimensional shingles.
Lap:
To cover the surface of one shingle or roll with another.
Lap cement:
An asphalt-based cement used to adhere overlapping plies of roll roofing.
Lean-to roof:
A roof with one slope only that is built against a higher wall.
LEED:
A green building rating system that stands for “Leadership in Energy and Environmental Design”. LEED is the nationally accepted standard for the design, construction and operation of high performance green buildings. LEED recognizes performance in five key areas: sustainable site development, energy efficiency, materials selection, indoor environmental quality and water savings.
Life-cycle cost:
The total lifetime cost of a roof. Calculated by adding maintenance costs to the installed price, then deducting the added value the roof provides when the home is resold.
Liquid Applied Membrane:
Generally applied to cast-in-place concrete surfaces in one or more coats to provide fully-adhered waterproof membranes which conform to all contours.
Loose-laid Membranes:
membranes that are not attached to the substrate except at the perimeter of the road and at penetrations. Typically, loose-laid membranes are held in place with ballast, such as water worn stone, gravel pavers, etc.
Low slope application:
Method of installing asphalt shingles on roof slopes between two and four inches per foot.
Low Temperature Flexibility
-The ability of a membrane to resist cracking/remain flexible after it has been exposed to low temperatures. Roofing membranes encounter extreme weather conditions and resisting cracking at low temperatures is vital to the long-term performance of roofing membranes in colder climates. Low temperature flexibility is directly related to the amount of rubber incorporated in the membrane. Since the rubber modifier also increases UV protection, the better the low temperature flexibility, the greater UV protection a membrane will have. Therefore, low temperature flexibility is vital in warmer climates as well.
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Mandrel:
A spindle or an axle used to secure or support material being machined or milled.
Mansard roof:
A type of roof containing two sloping planes of different pitch on each of four sides. The lower plane has a much steeper pitch than the upper, often approaching vertical. Contains no gables.
Masonry:
Anything constructed of such materials as bricks, stone, concrete blocks, ceramic blocks or concrete.
Mastic:
An asphalt-based cement used to bond roofing materials. Also known as flashing cement.
Material Safety Data Sheet (MSDS):
a written description of the chemicals within a product, and pertinent other data including such things as safe handling and emergency procedures.   MSDS Documents were re-formatted and are now called SDS (Safety Data Sheets.)  All SDS Documents can be seen here.
Mechanically-Fastened Membranes:
generally used to describe membranes that have been attached at defined intervals to the substrate. Mechanically fastening may be performed with various fasteners and/or other mechanical devices, such as plates or battens.
Metal drip edge:
A narrow strip of non-corrodible metal used at the rake and eave to facilitate water runoff.
MIL:
Measurement often used to determine thickness of a roofing membrane.    1 mil = .001 inch (1/1000) or 25.400 microns. 1 millimetre approx equal to 40 mils.
Mill Scale:
thin layers or flakes of metal that are usually remnants of the manufacturing process.  Mill Scale should be removed prior to application of any product.
Mineral-surfaced roofing:
Asphalt shingles and roll roofing that are covered with granules.
Modified Bitumen:
(1) a bitumen modified through the inclusion of one or more polymers (e.g., atactic polypropylene, styrene butadiene styrene, etc.); (2) composite sheets consisting of a polymer modified bitumen often reinforced as sometimes surfaced with various types of mats, films, foils and mineral granules.
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NOA (Notice of Acceptance)
An approval issued by the Miami-Dade County Product Control Division, identifying a product or assembly of products will perform as designed by the manufacturer to meet the Florida Building Code including the High Velocity Hurricane zone. See the Approvals page for Miami Dade.
National Roofing Contractors Association (NRCA):
An association of roofing, roof deck, and waterproofing contractors. The NRCA has the opinion that if an area retains water longer than 48 hours, it is not a roof; it is a pond.
Non-Ferrous:
A metal that does not contain, include or relate to iron.
Non-Potable:
Not fit or suitable for drinking.
Non-Sag:
A sealant formulation having a consistency that will permit application in vertical joints without appreciable sagging or slumping. A characteristic which allows the sealant to be installed in a sloped or vertical joint application without appreciable sagging or slumping.
Nonwoven:
a term used to describe fabrics, mats or scrims that are produced using processes other that weaving or knitting. Many nonwoven processes (i.e., spunbonded or wet laid, etc.) produce a random arrangement of reinforcing fibers (glass, polyester, etc.) in a mat or fabric.
Normal slope application:
Method of installing asphalt shingles on roof slopes between 4 inches and 21 inches per foot.
NSF:
Currently, the letters “NSF” do not stand for any specific words. Originally, they represented the “National Sanitation Foundation”. The organization name was changed to NSF International in the early 1990s when the National Sanitation Foundation and NSF Testing Labs were merged. The NSF performs testing on food, water and consumer goods to ensure that products are safe for consumption. 

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Organic felt:
An asphalt roofing base material manufactured from cellulose fibers.
Organic shingle:
An asphalt shingle reinforced with organic material manufactured from cellulose fibers.
OSD (or OSB) Plywood:
OSD plywood (which is also commonly known as OSB or oriented strand board) is produced by binding wood chips together with a mix of glue and resin. The mixture is then cast and baked to produce a plywood-like sheet. Because OSD does not use costly veneers it is as much as half the price of regular plywood. OSD also tends to have better waterproof characteristics, since the glue and resin make the wood chips impervious to moisture that can seep in between the plies of standard plywood. This means that OSD is the perfect choice for applications such as exterior wall sheathing and roofing. See CDX Plywood vs OSD (OSB) Plywood.
Overhang:
That portion of the roof structure that extends beyond the exterior walls of a building.
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Palletized Deck:
Wood framed floating deck
Pallets:
Wooden platforms used for storing and shipping bundles of shingles.  Standard shipping from Sealoflex:  24 - 5 gallon pails per pallet.
Parapet:
A low protective wall that extends above the roofline or balcony for support.
Peel Strength:
the average force (or force per unit width) required to peel a membrane or other material from the substrate to which it has been bonded.
Percent Elongation:
In tensile testing, the increase in the gauge length of a specimen measured at or after fracture of the specimen within the gauge length. This is usually expressed as a percentage of the original gauge length.
Perm:
A unit of water vapor transmission, defined as one grain of water vapor per square foot per hour per inch of mercury (Hg) pressure difference (1 inch of mercury = 0.491 psi).
Permeability:
The rate of flow of a liquid or gas through a porous material.
Pitch:
Also known as "slope", pitch is the measure of how "steep" a roof is. For example, if a roof is "4 in 12", the roof rises 4 inches for every horizontal run of 12 inches. The pitch of the roof is a big factor in determining the kinds of materials that can be used and the longevity of the roof. Usually, a steeper roof (higher pitch) will last longer due to its better drainage capabilities.
Plastic cement:
A compound used to seal flashings and in some cases to seal down shingles as well as for other small waterproofing jobs. Where plastic cement is required for sealing down shingles, use a dab about the size of a half dollar unless otherwise specified.
Ply:
The number of layers of roofing: i.e. one-ply, two-ply.
Ponding:
Water that remains on a roof 48 hours after a rain.
Porosity:
The density of substance and its capacity to pass liquids.
Portland Cement
A mixture of certain minerals which when mixed with water form a gray colored paste and cure into a very hard mass.
Positive Drainage:
The drainage condition of a roof where all water is gone from the roof surface within forty-eight hours of precipitation during normal drying conditions.
Potable:
Fit or suitable for drinking.
Pot Life:
The time interval following the addition of an accelerator before chemically curing material will become too viscous to apply satisfactorily.
Primer:
A material of relatively thin consistency applied to a surface for the purpose of creating a more secure bonding surface and to form a barrier to prevent migration of components. See Primer Chart.
Priming:
Sealing of a porous surface so that compounds will not stain, lose elasticity, shrink excessively, etc. because of loss of oil or vehicle into the surround.
Projection:
In roofing, any object or equipment which pierces the roof membrane.
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Racking:
Roofing application method in which shingle courses are applied vertically up the roof rather than across and up. Not a recommended procedure.
Rafter:
The supporting framing member immediately beneath the deck, sloping from the ridge to the wall plate.
Rake:
The inclined edge of a sloped roof over a wall from the eave to the ridge.
Release tape:
A plastic or paper strip that is applied to the back of self-sealing shingles. This strip prevents the shingles from sticking together in the bundles, and need not be removed for application.
Re-cover (overlay):
The installation of a new roof system over an existing system without removing an existing system.
Re-roofing:
Installing a new roof system on a building that is not new.
Retaining Wall:
A structure that holds back earth. Retaining walls stabilize soil and rock from down slope movement or erosion and provide support for vertical or near-vertical grade changes.
Ridge:
The uppermost, horizontal external angle formed by the intersection of two sloping roof planes.
Ridge shingles:
Shingles used to cover the horizontal external angle formed by the intersection of two sloping roof planes.
Rise:
The vertical distance from the eaves line to the ridge.
Roll roofing:
Asphalt roofing products manufactured in roll form.
Roof Nav:
A password-protected software tool accessible on the FM Approval website which allows users access to the roof-specific portions of the FM Approvals Guide. The RoofNav tool can be used to search the FM Global Database to create a roofing assembly that meets the requirements of FM Approvals.
Roof Slope :
Roof slope is the most important factor in roof design. The slope of a roof effects the interior volume of a building, drainage, style, and material used for the roof covering. If water collects on the roof (no or poor drainage), the cause is probably related to the slope. Slope is the angle made by the roof surface plane with the horizontal plane and expressed as the amount of vertical rise for every twelve inch (12") horizontal run. For instance, a roof that rises four inches (4") for every twelve inch (12") horizontal run, is expressed as having a "four in twelve" slope; often written as "4:12." Expressed as a percentage, the slope would be 33%, which is equal to 4 divided by 12. Also known as the Roof Pitch. Some common roof slopes and the terms that classify them are: * Flat Roof: 2/12 * Low Slope: 2/12-4/12 * Conventional Slope Roof: 4/12-9/12 * Steep Slope: 9/12 and higher
Roofing tape:
An asphalt-saturated tape used with asphalt cements for flashing and patching asphalt roofing.
Run:
The horizontal distance from the eaves to a point directly under the ridge. One half the span.
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Safety Data Sheet (SDS)
An SDS (Safety Data Sheet) and an MSDS (Material Safety Data Sheet) are the same. They are documents that accompany hazardous chemicals and substances and outline the dangers, composition, safe handling, and disposal of the said chemicals and substances. MSDS documents were standardized in 2015/2016 to a new format to become SDS Documents. They are constructed and formatted to conform to the Globally Harmonized System (GHS), which mandates SDS’s have 16 standardized sections, arranged in a strict order. See all SDS Documents here.
Saturant:
Asphalt used to impregnate an organic felt base material.
SBS (Styrene Butadiene Styrene)Modified:
Roofing material with a modifier of asphalt (see modified bitumen) that enhances the bitumen’s ability to resist the effects of weather and aging.
Screeding:
The wood or metal straightedge used to strike off or level newly placed concrete when doing cement work. Screeds can be the leveling device used or the form work used to level or establish the level of the concrete. Screeds can be hand used or mechanical.
Scrim
The reinforcing fabric that acts as a carrier for polymer modified bitumen. The scrim contributes to performance characteristics of the finished product that include puncture resistance, tensile strength and fire resistance. The two primary fabrics for scrim include fiberglass and polyester. A combination scrim, which incorporates both of these fabrics, also exists.
Scupper:
An outlet in the wall of a building or a parapet wall for drainage of water from a flat roof.
Self-sealing strip or spot:
Factory-applied adhesive that bonds shingle courses together when exposed to the heat of the sun after application. Also known as self-sealing cement.
Selvage:
That portion of roll roofing overlapped by the succeeding course to obtain double coverage.
Shelf Life:
Used in the glazing and sealant business to refer to the length of time a product may be stored before beginning to lose its effectiveness. Manufacturers usually state the shelf life and the necessary storage conditions on the package.  
Sheathing:
Exterior grade boards used as a roof deck material. "Step sheathing" is used alone or in combinations with solid sheathing for installation of tiles or shakes. Step sheathing allows air circulations under the tiles by using 1-by-6 or 2-by-6 boards that are evenly spaced so that air can move under the tiles or shakes.
Shed roof:
A roof containing only one sloping plane. This type roof has no hips, ridges, valleys or gables.
Single coverage:
Asphalt roofing that provides one layer of roofing material over the deck.
Single Ply:
A descriptive term signifying a roof membrane composed of only one layer of material such as EPDM, Hypalon or PVC.
Shore A Hardness:
The relative hardness of elastic materials such as rubber or soft plastics can be determined with an instrument called a Shore A durometer. If the indenter completely penetrates the sample, a reading of 0 is obtained, and if no penetration occurs, a reading of 100 results. The reading is dimensionless.
Slope:
The degree of roof incline expressed as the ratio of the rise, in inches, to the run, in feet. (See Roof Slope in this glossary.)
Smooth-surfaced roofing:
Roll roofing that is covered with ground talc or mica instead of granules (coated).
Solar Absorptivity :
Solar Absorptivity is a fraction which represents the difference between how much solar radiation is absorbed by a material versus that which is absorbed by a standard black surface. Since black (dark) surfaces absorb more solar energy than lighter colors (i.e., do not reflect as much), those surfaces are warmer. See Solar Absorptivity Chart.
Spalling:
describes surface failure in which chips are shed from a contact point. This is due to the maximal shear stress being not at the surface but just below it. One form of spalling occurs due to moisture freezing inside cracks in rock, cracking off the outer surfaces. Spalling can occur on a concrete surface if exposed to salt or if improperly finished.
Specification
Detailed written instructions which, when clear and concise, explain each phase of work to be done.
Soffit:
The finished underside of the eaves.
Soil stack:
A vent pipe that penetrates the roof.
Span:
The horizontal distance from eaves to eaves.
Specialty eaves flashing membrane:
A self-adhering, waterproofing shingle underlayment designed to protect against water infiltration due to ice dams or wind-driven rain.
Square:
A unit of roof measure covering 100 square feet.
Square-tab shingles:
Shingles on which tabs are all the same size and exposure.
Standing Seam
Is a term used to describe the adjoining of two metal panels together with an upturned portion of the metal. The two panels are held together with concealed clips.
Steep slope application:
Method of installing asphalt shingles on roof slopes greater than 21 inches per foot.
Step flashing:
Flashing application method used where a vertical surface meets a sloping roof plane.
Strip shingles:
Asphalt shingles that are approximately three times as long as they are wide.
Substrate:
The surface, or material onto which systems are applied.
Surface Temperature:
The temperature of the surface of the roof, wall, etc. of the project.
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Tar paper:
Felt paper.
Tear off:
A term used to describe the complete removal of the built up roof membrane and insulation down to and exposing the roof deck.
Tensile Strength
The maximum force a material can bear without tearing apart. Roofing membranes should have sufficient tensile strengths to resist the severe stresses caused by internal and external forces imposed on it. Thermal shock, caused by sudden heating or cooling of a membrane, causes stress that a roofing membrane must be able to withstand. The greater the tensile strength of a membrane, the greater resistance it will have to splitting, breaking or tearing.
Thermal Movement:
The measured amount of dimensional change that a material exhibits as it is warmed or cooled.
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UL:
Underwriters Laboratories, Inc.
UL label:
Label displayed on packaging to indicate the level of fire and/or wind resistance of asphalt roofing.
Underlayment:
A layer of asphalt saturated (sometimes referred to as tar paper) which is laid down on a bare deck before shingles are installed to provide additional protection for the deck.
UV Resistance:
The ability of a roof material to prevent degradation caused by exposure to Ultraviolet rays. Heat and UV are the two primary causes of premature roof failure.  Oils in roofing membranes provide pliability.  UV rays cause these oils dry out; this leads to the cracking of the roofing membrane.  The addition of unique polymers maintains the membrane’s pliability which protects it from cracking and thus extends the waterproofing life of the membrane
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Valley:
The internal angle formed by the intersection of two sloping roof planes to provide water runoff.
Viscosity:
The internal frictional resistance offered by a fluid to change of shape or to the relative motion or flow of its parts.
Vent:
Any outlet for air that protrudes through the roof deck such as a pipe or stack. Any device installed on the roof, gable or soffit for the purpose of ventilating the underside of the roof deck.
Vent sleeve:
Refer to "Collar".
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Waterproofing:
A term which refers to the process where a building component is made totally resistant to the passage of water and/or water vapor.
Water Repellant (Coating):
Coating or sealer applied to the surface of concrete and masonry surfaces to repel water.
Water Vapor:
Moisture existing as a gas in air.
Wind Uplift:
The upward force exerted by wind traveling across a roof.

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