the ability to resist being worn away by contact with another moving, abrasive surface, such as foot traffic, mechanical equipment, wind-blown particles, etc.
Tag: measurement
Absorption
The ability of a material to accept within its body, quantities of gases or liquid, such as moisture
Adhesion
A steady or firm attachment.
Aged R-value
Thermal resistance value established by utilizing artificial conditioning procedures for a prescribed time period.
Application Rate
The average quantity (mass, volume or thickness) of material applied per unit area.
British Thermal Unit (BTU)
The heat energy required to raise the temperature of 1 pound of water degree Fahrenheit (joule). For the metric equivalent, see Joule.
Capacitance Meter
A device used to locate moisture or wet materials within a roof system by measuring the ratio of the change to the potential difference between two conducting elements separated by a non-conductor.
Centipoise
A unit of measure of absolute viscosity. (The viscosity of water is one centipoise. The lower the number, the less viscous the material.)
Centistoke
A unit of viscosity; the ratio of a liquid’s absolute viscosity to the density of that liquid.
Chalk Line
A line made on the roof or other flat surface by snapping a taut string or cord dusted with colored chalk.
Chemical Resistance
The ability to withstand contact with specified chemicals without a significant change in properties
Coefficient of Thermal Expansion
The coefficient of change in dimension of a material per unit of dimension per degree change in temperature.
Cohesion
The molecular forces of attraction by which the body of a material is held together.
Color Stability
The ability of a material to retain its original color after exposure to weather.
Compressive Strength
The property of a material that relates to its ability to resist compression loads.
Coverage
The surface area uniformly covered by a specific quantity of a particular material at a specific thickness.
Cream Time
Time in seconds (at a given temperature) when the A and B components of polyurethane foam will begin to expand after being mixed. Recognizable as a change in color of the materials.
Cure Time
The time required for a material to reach its desirable long-term physical characteristics.
Dead Level
absolutely horizontal or zero slope. (see Slope.)
Dead loads
The weight of a structure itself, including the weight of fixtures or equipment permanently attached to it.
Degree Days
A unit used in estimating the fuel consumption for a building; equal to the number of degrees that the mean temperature, for a 24-hour day, is below the “base temperature”; the base temperature is taken as 65° F (18.3° C) in the U.S.A.
Design Loads
The total load on a structural system for the most severe combination of loads and forces which it is designed to sustain.
Dew Point
The temperature at which air becomes saturated with water vapor. The temperature at which air has a relative humidity of 100%.
Dimensional Stability
The degree to which a material maintains its original dimensions when subjected to changes in temperature and humidity.
Drag Load
The external force (e.g., from the weight of ice and snow) applied to a steep-slope roof system component forcing the component downslope.
Dry Bulb Temperature
The temperature of air as measured by an ordinary thermometer.
Dry Film Thickness
The thickness, expressed in mils, of an applied and cured coating or mastic. For comparison, see Wet film thickness.
Drying Time
The time required for the loss of volatile components so that the material will no longer be adversely affected by weather conditions such as dew, rain, or freezing.
Dynamic Load
Any load which is nonstatic, such as a wind load or moving live load.
Eave Height
The vertical dimension from finished grade to the eave.
Eave Trough
See Gutter
Elasticity
The property of a body that causes it to tend to return to its original shape after deformation (as stretching, compression or torsion).
Elongation
The ratio of the extension of a material to the length of the material prior to stretching.
Equilibrium Moisture Content (EMC)
(1) the moisture content of a material stabilized at a given temperature and relative humidity, expressed as percent moisture by weight.
Equiviscous Temperature (EVT)
The temperature at which a bitumen attains the proper viscosity for built-up membrane application.
Equiviscous Temperature (EVT) Application Range
The recommended bitumen application temperature range. The range is approximately 25° F (14° C) above or below the EVT, thus giving a range of approximately 50° F (28° C). The EVT range temperature is measured in the mop cart or mechanical spreader just prior to application of the bitumen to the substrate.
For Asphalt
- Mop Application: the temperature at which the asphalt’s apparent viscosity is 125 centipoise (0.125 Pa·s).
- Mechanical Spreader Application: the temperature at which the asphalt’s apparent viscosity is 75 centipoise (0.075 Pa·s).
Note: In order to avoid the use of two kettles if there are simultaneous mop and mechanical spreader applications, the EVT for mechanical spreader application can be used for both application techniques.
For Coal Tar
- the recommended EVT for roofing coal tar (ASTM D 450, Type I or III) is the temperature at which the coal tar’s apparent viscosity is 25 centipoise (0.025 Pa·s).
Exposure
(1) the traverse dimension of a roofing element or component not overlapped by an adjacent element or component in a roof covering. For example, the exposure of any ply in a built-up roof membrane may be computed by dividing the felt width, minus 2 inches (51 mm), by the number of shingled plies; thus, the exposure of 36 inch (914 mm) wide felt in a shingled, four-ply membrane should be approximately 8½ inches (216 mm) (See Figure 8); (2) the dimension of sidewall or roofing covering that is not covered or overlapped by the up slope course of component. The typical exposure for a standard-sized, three-tab shingle is 5 inches (127 mm), depending on manufacturer specifications.
Factory Mutual Research (FMR)
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.
Fading
Any lightening of initial color.
Film Thickness
The thickness of a membrane or coating. Wet film thickness is the thickness of a coating as applied; dry film thickness is the thickness after curing. Film thickness is usually expressed in mils (thousandths of an inch).
Fire Resistance
The property of a material or assembly to withstand fire or give protection from it.
Flame Spread
The propagation of a flame away from its source of ignition.
Flash Point
The lowest temperature at which vapors above a volatile combustible substance ignite in air when exposed to a flame.
Force
A strength or energy exerted or brought to bear; cause of motion or change.
Gauge
A metal thickness measurement.
Grain
A unit of measure in the English System of units; 7,000 grains equals 1 lb.; used as a measure of the weight of moisture in air.
Groundwater Level
At a particular site, the level, below which the subsoil and rock masses of the earth are fully saturated with water.
Hue
The subjective perception of color such as red, yellow, green, blue, purple or some combination; white, black or gray possess no hue.
Humidity
The condition of the atmosphere with respect to water vapor. See relative humidity.
Ignition Temperature
The lowest temperature at which combustion will occur spontaneously under specific conditions.
Impact Resistance
Resistance to fracture under the sudden application of an exerted force.
Joule
A unit of energy or work; equals the work done by a force of 1 newton which acts over a distance of 1 meter in the direction of the force.
K or K-Value
Thermal conductivity; the time rate of heat flow through a unit area of a homogeneous material in a direction perpendicular to isothermal planes induced by a unit temperature gradient. In English (inch-pound) units of measurement, it is the number of BTUS that pass through a 1 inch (25 mm) thickness of a 1 square foot (0.09 m2) sample of material in 1 hour with a temperature difference between the two surfaces of 1° F. It is expressed as Btu·inch/h·ft2·°F.
Kesternich Test
Simulates acid rain conditions by subjecting test specimens to a sulfur dioxide atmosphere as well as condensing moisture for the purpose of evaluating rust/corrosion characteristics.
Lift
The sprayed polyurethane foam that results from a pass. It usually is associated with a certain pass thickness and has a bottom layer, center mass and top skin in its makeup.
Low Temperature Flexibility
The ability of a membrane or other material to resist cracking when flexed after it has been cooled to a low temperature.
Material Safety Data Sheets
A written description of the chemicals in a product and other pertinent data, including such things as safe handling and emergency procedures. In accordance with OSHA regulations, it is the manufacturer’s responsibility to produce an MSDS and the employers responsibility to communicate its contents to employees.
Meter
Unit of length measurement in the metric system; 1 meter is equal to 39.37 inches.
Mil
A unit of measure, one mil is equal to 0.001 inches, or 25.4 micrometers (µm), often used to indicate the thickness of a roofing membrane.
Millimeter
A unit of measure equal to one thousandth (0.001) of a meter, or 0.03937 inches.
Newton (N)
SI unit of measure for force.
Non-Volatile Content
The portion of a coating that does not evaporate during drying or curing under specified conditions, comprising the binder and, if present, the pigment. (The percent volatile content is obtained by subtracting the nonvolatile content from 100.).
Open Time
The period of time after an adhesive has been applied and allowed to dry, during which an effective bond can be achieved by joining the two surfaces.
Ozone Resistance
The ability of a material to resist the deteriorating effects of ozone exposure.
Peel Strength
The average load per unit width required to separate progressively a flexible member from a rigid member or another flexible member.
pH
a measure of the acidity or alkalinity of a solution, with neutrality represented by a value of 7, with increasing acidity represented by increasingly smaller values, and with increasing alkalinity represented by increasingly larger values.
Puncture Resistance
The ability of a material to withstand the action of a penetrating or puncturing object.
Roof Slope
The angle a roof surface makes with the horizontal, expressed as a ratio of the units of vertical rise to the units of horizontal length (sometimes referred to as run). For English units of measurement, when dimensions are given in inches, slope may be expressed as a ratio of rise to run, such as 4:12 or as an angle.
Run
Horizontal dimension of a slope.
Service Temperature Limits
The minimum or maximum temperature at which a coating, SPF or other material will perform satisfactorily.
Shading
Slight differences in surfacing color, such as shingle granule coloring, that may occur as a result of manufacturing operations.
Shear Strength
The resistance to forces that cause or tend to cause two contiguous parts of a body to slide relative to each other in a direction parallel to their contrast.
Shelf Life
The maximum time a packaged material can be stored under specified conditions and still meet the performance requirements specified.
Shrinkage
A decrease in one or more dimensions of an object or material.
Slope
The angle of incline, usually expressed as a ratio of rise to run, or as an angle.
Softening Point
The temperature at which bitumen becomes soft enough to flow, as determined by an arbitrary, closely defined method (ASTM Standard test method D 36 or D 3461).
Tensile Strength
The strength of a material under tension as distinct from torsion, compression or shear.
Thermal Conductance
The thermal transmission in unit time through unit area of a particular body or assembly having defined surfaces, when unit average temperature difference is established between the surfaces. C=Btu/h·ft2·°F (C=W/m2·K).
Thermal Conductance (C)
The time rate of heat flow through a unit area of a body induced by a unit temperature difference between bodies. In English (inch-pound) units of measurement, the number of BTUs that pass through a specified thickness of a one square foot (0.09 m2) sample of material in one hour with a temperature difference between the two surfaces of 1° F. In English (inch-pound) units it is expressed as Btu/h·ft2·F. Note 1: A thermal conductance (C) value applies to a specific thickness of a specific material. Note 2: It is mathematically incorrect to multiply or divide the thermal conductance (C) value for a specific thickness of a material to determine the thermal conductance value of a different thickness of the same material. Note 3: It is mathematically incorrect to add thermal conductance (C) values to determine overall thermal performance. If it is necessary to determine the overall thermal performance of a construction, it is appropriate to convert the individual thermal conductance (C) values to thermal resistance (R) values (i.e., R= 1/c), and then add the thermal resistance values (i.e., RT=R1, + R2 + …).
Thermal Conductivity (k)
The time rate of heat flow through a unit area of a homogeneous material in a direction perpendicular to isothermal planes induced by a unit temperature gradient is called thermal conductivity (k or kvalue). In English (inch-pound) units of measurement, it is the number of BTUs that pass through a 1 inch (25 mm) thickness of a 1 square foot (0.09 m2) sample of material in one hour with a temperature difference between the two surfaces of 1°F. In English (inch-pound) units it is expressed as Btu·inch/h·ft2·°F. Note 1: A thermal conductivity (k) value applies to 1 inch (25 mm) thickness of a specific material. Note 2: It is mathematically incorrect to add, multiply, or divide the thermal conductivity (k) value of a material to determine the thermal performance value of a different thickness of the same material. If it is necessary to determine the thermal performance of a specific thickness of a material, it is appropriate to convert the thermal conductivity (k) of the material to a thermal resistance (R) value (i.e., R = 1/k), and then perform the mathematical calculation.
Thermal Resistance (R)
Under steady conditions, thermal resistance is the mean temperature difference between two defined surfaces of material or construction that induces unit heat flow through a unit area. In English (inch·pound) units it is expressed as °F·ft2·h/Btu. Note 1: A thermal resistance (R) value applies to a specific thickness of a material or construction. Note 2: The thermal resistance (R) of a material is the reciprocal of the thermal conductance (C) of the same material (i.e., R = 1/C). Note 3: Thermal resistance (R) values can be added, subtracted, multiplied, and divided by mathematically appropriate methods.
Thermal Transmittance (U or U-Factor)
Thermal transmittance (U or U-factor) is the time rate of heat flow per unit area under steady conditions from the fluid (e.g., air) on the warm side of a barrier to the fluid (e.g., air) on the cold side, per unit temperature difference between the fluids. In English (inch·pound) units expressed as Btu/h·ft2·°F. Note 1: A thermal transmittance (U) value applies to the overall thermal performance of a system (e.g., roof assembly). Note 2: Thermal transmittance (U) is sometimes called the overall coefficient of heat transfer. Note 3: Thermal transmittance (U) is reciprocal of the overall thermal resistance (RT) of a system (i.e., U = 1/RT).
Water Table
The level within the ground, below which the soil is saturated with water.
Water Vapor Transmission
A measure of the rate of transmission of water vapor through a material under controlled laboratory conditions of temperature and humidity. Customary units are grains/h·ft2.
Water-Shedding
The ability of individual, overlapping components to resist the passage of water without hydrostatic pressure.
Waterproof
The quality of a membrane, membrane material, or other component to prevent water entry.
Waterproofing
Treatment of a surface or structure to prevent the passage of water under hydrostatic pressure.
Wet Bulb Temperature
The temperature of air as registered by a thermometer whose bulb is covered by a water wetted wick.
Wet Film Thickness
The thickness, expressed in mils, of a coating or mastic as applied but not cured. For comparison, see Dry film thickness.
Wind Load
Force exerted by the wind on a structure or part of a structure.
Yield
In SPF-based roofing, the volume of foam per unit weight, normally expressed as board feet per pound or board feet per 1000 pounds.