Construction Terms

Science dealing with the production, control, transmission, reception and effects of sound, and the process of hearing.
Sand, gravel, crushed stone or other material that is a main constituent of Portland Cement, concrete and aggregated gypsum plaster. Also, polystyrene, perlite and vermiculite particles used in texture finishes.
American Insurance Assn., successor to the National Board of Fire Underwriters and a nonprofit organization of insurance companies. Also, American Institute of Architects.
Airborne Sound
Sound traveling through the medium of air.
Metal securing device embedded or driven into masonry, concrete, steel or wood.
Anchor Bolt
Heavy, threaded bolt embedded in the foundation to secure sill to foundation wall or bottom plate of exterior wall to concrete floor slab.
Annular Ring Nail
A deformed shank nail with improved holding qualities specially designed for use with gypsum board.
American National Standards Institute, a nonprofit, national technical association that publishes standards covering definitions, test methods, recommended practices and specifications of materials. Formerly American Standards Assn. (ASA) and United States of America Standards Institute (USASI).
Area Separation Wall
Residential fire walls, usually with a 2- to 4-hour rating, designed to prevent spread of fire from an adjoining occupancy; extends from foundationGlossFoundation.1041 to or through the roof. Identified by codes as either "fire wall", "party wall" or "townhouse separation wall."
Formerly American Standards Assn., now American National Standards Institute (ANSI).
Formerly American Society for Testing and Materials, now ASTM, a nonprofit, national technical society that publishes definitions, standards, test methods, recommended installation practices and specifications for materials.
Reduction in sound level.
Back Blocking
A short piece of gypsum board adhesively laminated behind the joints between each framing member to reinforce the joint.
Backup Strips
Pieces of wood nailed at the ceiling-sidewall corner to provide fastening for ends of plaster base or gypsum panels.
Balloon Frame
Method of framing outside walls in which studs extend the full length or height of the wall.
Bar Joist
Open-web, flat truss structural member used to support floor or roof structure. Web section is made from bar or rod stock, and chords are usually fabricated from "T" or angle sections.
Narrow strip of wood, plastic, metal or gypsum board used to conceal an open joint.
Board for the Coordination of Model Codes; part of the Council of American Building Officials Association (CABO).
Loadbearing member spanning a distance between supports.
Support area upon which something rests, such as the point on bearing walls where the weight of the floor joist or roof rafter bears.
To set firmly and permanently in place.
Bowing of a member that results when a load or loads are applied laterally between supports.
Board Foot (Bd. Ft.)
Volume of a piece of wood, nominal 19 x 129 x 18. All lumber is sold by the board-foot measure.
Bonding Agent
A compound that will hold materials together by bonding to the surfaces to be joined.
Brick Veneer
Non-loadbearing brick facing applied to a wall to give appearance of solid-brick construction; bricks are fastened to backup structure with metal ties embedded in mortar joints.
Members attached between floor joists to distribute concentrated loads over more than one joist and to prevent rotation of the joist. Solid bridging consists of joist-depth lumber installed perpendicular to and between the joists. Cross-bridging consists of pairs of braces set in an "X" form between joists.
Council of American Building Officials Association, made up of representatives from three model codes. Issues National Research Board (NRB) research reports.
Curvature built into a beam or truss to compensate for loads that will be encountered when in place and load is applied. The crown is placed upward. Insufficient camber results in unwanted deflection when the member is loaded.
Cant Beam
Beam with edges chamfered or beveled.
Cant Strip
Triangular section laid at the intersection of two surfaces to ease or eliminate effect of a sharp angle or projection.
Carrying Channel
Main supporting member of a suspended ceiling system to which furring members or channels attach.
Glazed sash or frame hung to open like a door.
The trim around windows, doors, columns or piers.
Cement Board
A factory-manufactured panel, 1/4" to 3/4" thick, 32" to 48" wide, and 3' to 10' long, made from aggregated and reinforced portland cement.
Chalk Line
Straight working line made by snapping a chalked cord stretched between two points, transferring chalk to work surface.
A non-load-bearing exterior wall enclosing a building. It may be brick, aluminum, steel, bronze, plastic, glass, stone, or other acceptable material.
Coefficient of Heat Transmission (U)
Total amount of heat that passes through an assembly of materials, including air spaces and surface air films. Expressed in Btu per hr., per sq. ft., per °F temperature difference between inside and outside air (beyond the surface air films). "U" values are often used to represent wall and ceiling assemblies, floors and windows. Note: "k" and "C" values cannot simply be added to obtain "U" values. "U" can only be obtained by adding the thermal resistance (reciprocal of "C") of individual items and dividing the total into 1.
Coefficient of Hygrometric Expansion
See Hygrometric Expansion.
Coefficient of Thermal Conductance (C)
Amount of heat (in Btu) that passes through a specific thickness of a material (either homogeneous or heterogeneous) per hr., per sq. ft., per °F. Measured as temperature difference between surfaces. The "C" value of a homogeneous material equals the "k" value divided by the material thickness: C = k/t (where t = thickness of material in inches) It is impractical to determine a "k" value for some materials such as building paper or those only used or formed as a thin membrane, so only "C" values are given for them.
Coefficient of Thermal Conductivity (k)
Convenient factor represents the amount of heat (in Btu) that passes by conduction through a one inch thickness of homogeneous material, per hr., per sq. ft., per °F. Measured as temperature difference between the two surfaces of the material.
Coefficient of Thermal Expansion
See Thermal Expansion.
Vertical loadbearing member.
Force that presses particles of a body closer together.
Compressive Strength
Measures maximum unit resistance of a material to crushing load. Expressed as forceGlossForce.1040 per unit cross-sectional area, e.g., pounds per square inch (psi).
Concrete Footing
Generally, the wide, lower part of a foundation wall that spreads the weight of the building over a larger area. Its width and thickness vary according to weight of building and type of soil on which building is erected.
Conduction, Thermal
Transfer of heat from one part of a body to another part of that body, or to another body in contact, without any movement of bodies involved. The hot handle of a skillet is an example. The heat travels from the bottom of the skillet to the handle by conduction.
Process of heat carried from one point to another by movement of a liquid or a gas (i.e., air). Natural convection is caused by expansion of the liquid or gas when heated. Expansion reduces the density of the medium, causing it to rise above the cooler, more dense portions of the medium. Gravity heating systems are examples of the profitable use of natural convection. The air, heated by the furnace, becomes less dense (consequently lighter) and rises, distributing heat to the various areas of the house without any type of blower. When a blower is used, the heat transfer method is called "forced convection."
Corner Brace
Structural framing member used to resist diagonal loads that cause racking of walls and panels due to wind and seismic forces. May consist of a panel or diaphragm, or diagonal flat strap or rod. Bracing must function in both tension and compression. If brace only performs in tension, two diagonal tension members must be employed in opposing directions as "X" bracing.
Corner Post
Timber or other member forming the corner of a frame. May be solid or built-up as a multi-piece member.
Short stud such as that used between a door or window header and the top plate.
Curtain Wall
Exterior wall of a building that is supported by the structure and carries no part of the vertical load except its own. Curtain walls must be designed to withstand wind loads and transfer them to the structure.
Cycle (Acoustic)
One full repetition of a motion sequence during periodic vibration. Movement from zero to +1 back to zero to -1 back to zero. Frequency of vibration is expressed in Hertz (cycles per second -- see Frequency).
Dead Load
Load on a building element contributed by the weight of the building materials.
Decibel (dB)
Adopted for convenience in representing vastly different sound pressures. The sound pressure level (SPL) in decibels is 10 times the logarithm to the base 10 of the squared ratio of the sound pressure to a reference pressure of 20 micropascals. This reference pressure is considered the lowest value at 100 Hz that the ear can detect. For every 10 dB increase or decrease in SPL, a sound is generally judged to be about twice or half as loud as before the change.
Separation of elements to reduce or eliminate the transfer of sound, heat or physical loads from one element to the other.
Displacement that occurs when a load is applied to a member or assembly. The dead load of the member or assembly itself causes some deflection as may occur in roofs or floors at mid-span. Under applied wind loads maximum deflection occurs at mid-height in partitions and walls.
Deflection Limitation
Maximum allowable deflection is dictated by the bending limit of the finish material under the required design load (e.g., usually 5 psf for interior partitions). Often expressed as ratio of span (L) divided by criterion factor (120, 180, 240, 360). For example, in a 108 or 120" high wall, allowable deflection under L/240 criterion equals 120"/240 or 1/2" maximum. Selection of limiting heights and spans are frequently based on minimum code requirements and accepted industry practice as follows: (a) L/120 for gypsum panel surfaces and veneer plaster finish surfaces, (b) L/240 for conventional lath and plaster surfaces, (c) L/360 for mechanically attached marble or heavy stone to walls; however, support for its own weight should be from the floor or separate supports. Although some building codes permit these deflections, more conservative criteria are frequently advised so that applied loads are not visible or aesthetically unacceptable.
Change in shape of a body brought about by the application of a force internal or external. Internal forces may result from temperature, humidity or chemical changes. External forces from applied loads can also cause deformation.
Design Load
Combination of weight (dead load) and other applied forces (live loads) for which a building or part of a building is designed. Based on the worst possible combination of loads.
Dew Point
The temperature at which air becomes saturated with moisture and below which condensation occurs.
Door Buck
Structural element of a door opening. May be the same element as the frame if frame is structural, as in the case of heavy steel frames.
Double-Hung Window
Window sash that slides vertically and is offset in a double track.
Interruption or offset in an exterior horizontal surface, such as a soffit, immediately adjacent to the fascia. Designed to prevent the migration of water back along the surface.
Generic term for interior surfacing material, such as gypsum panels, applied to framing using dry construction methods, e.g., mechanical fasteners or adhesive. See SHEETROCK brand Gypsum Panels.
Exterior Insulation and Finish System (E
Exterior cladding assembly consisting of a polymer finish over a reinforcement adhered to foam plastic insulation that is fastened to masonry, concrete, building sheathing or directly to the structural framing. The sheathing may be cement board or gypsum sheathing.
To project tested values, assuming a continuity of an established pattern, to obtain values beyond the limit of the test results. Not necessarily reliable.
Factor of Safety
Ratio of the ultimate unit stress to the working or allowable stress.
Fascia Board
Board fastened to the ends of the rafters or joists forming part of a cornice.
Fast Track
Method that telescopes or overlaps traditional design-construction process. Overlapping phases as opposed to sequential phases is keynote of the concept.
Condition of material under stress that has lost, to some degree, its power of resistance as a result of repeated application of stress, particularly if stress reversals occur as with positive and negative cyclical loading.
Fire Endurance
Measure of elapsed time during which an assembly continues to exhibit fire resistance under specified conditions of test and performance. As applied to elements of buildings, it shall be measured by the methods and to the criteria defined in ASTM. Methods E119, Fire Tests of Building Construction and Materials; ASTM Methods E152, Fire Tests of Door Assemblies; ASTM Methods E814, Fire Test of Through-Penetration Fire Stops; or ASTM Methods E163, Fire Tests of Window Assemblies.
Fire Resistance
Relative term, used with a numerical rating or modifying adjective to indicate the extent to which a material or structure resists the effect of fire.
Fire Stop
Obstruction in a cavity designed to resist the passage of flame, sometimes referred to as "fire blocking."
Fire Taping
The taping of gypsum board joints without subsequent finishing coats. A treatment method used in attic, plenum or mechanical areas where aesthetics are not important.
Fire Wall
Fire-resistant partition extending to or through the roof of a building to retard spread of fire. See Area Separation Wall.
Refers to properties or designs to resist effects of any fire to which a material or structure may be expected to be subjected.
Denotes substantially lower degree of fire resistance than fire-resistive. Often used to describe materials that are combustible but have been treated to retard ignition or spread of fire under conditions for which they were designed.
Use of this term in reference to buildings is discouraged because few, if any, building materials can withstand extreme heat for an extended time without some effect. The term "fire-resistive" or "resistant" is more descriptive.
Flame Spread
Index of the capacity of a material to spread fire under test conditions, as defined by ASTM Standard E84. Materials are rated by comparison with the flame-spread index of red oak flooring assigned a value of 100 and inorganic reinforced cement board assigned a value of 0.
Capability of a combustible material to ignite easily, burn intensely or have rapid rate of flame spread.
Flanking Paths
Paths by which sound travels around an element intended to impede it, usually some structural component that is continuous between rooms and rigid enough to transmit the sound. For example, a partition separating two rooms can be "flanked" by the floor, ceiling or walls surrounding the partition if they run uninterrupted from one room to the other. Ducts, conduits, openings, structural elements, rigid ties, etc., can be sound flanking paths. The acoustic effect of sound flanking paths is dependent on many factors.
Strips of metal or waterproof material used to make joints waterproof, as in the joining of curtain wall panels.
Lower extremity of a foundation or loadbearing member that transmits load to load-bearing substrate.
Amount of applied energy to cause motion, deformation or displacement and stress in a body.
Component that transfers weight of building and occupants to the earth.
Frequency (Sound)
Number of complete vibrations or cycles or periodic motion per unit of time.
Member or means of supporting a finished surfacing material away from the structural wall or framing. Used to level uneven or damaged surfaces or to provide space between substrates. Also an element for mechanical or adhesive attachment of paneling.
Uppermost portion of the end wall of a building that comes to a triangular point under a sloping roof.
Gauging Plaster
Combine with lime putty to provide setting properties, to increase dimensional stability during drying, and to provide initial surface hardness in lime finish coats.
Beam, especially a long, heavy one; the main beam supporting floor joists or other smaller beams.
An inorganic mixture that has been fused at a high temperature and cooled without crystallization.
Wood or metal plate riveted, bolted, glued or pressed (wood trusses) over joints to transfer stresses between connected members.
Form of energy thought to be characterized by the rate of vibration of the molecules of a substance. The hotter the substance, the faster the molecules vibrate. On the other hand, when there is no heat present it is thought the molecules will be at rest, which theoretically occurs at absolute zero, -459.7°F (-273.15°C or 0.0°K).
Heat Quantity (Btu)
Common unit of measure of the quantity of heat is the British Thermal Unit (Btu). One Btu is the amount of heat required to raise one pound of water from 63° to 64°F (1 Btu = 1055.06 J). This is about the amount of heat given off by one wooden match. A pound of coal can produce 13,000 Btu.
Heat Transfer
Heat always flows toward a substance of lower temperature until the temperatures of the two substances equalize. It travels by one or more of three methods: conduction, convection or radiation.
Heel of Rafter
Seat cut in a rafter that rests on the wall plate.
The units of measure of sound frequency, named for Heinrich H. Hertz. One Hertz equals one cycle per second.
Hollow Brick
A clay masonry unit whose net cross sectional area in the plane of the bearing surface is not less than 60 percent of the gross cross sectional area of that face.
Any substance having cells suggesting a mass of cells such as those built by the honeybee. Some hollow-core doors use the honeycomb principle in their construction.
Housing and Urban Development, federal agency.
HUD Mobile Home Standards
Officially, the National Mobile Home Construction and Safety Standards Act of 1974 for construction of mobile homes. Includes the following agencies: DAPIA Design Approval Primary Inspection Agency and IPIA Production Inspection Primary Inspection Agency.
Heating, ventilating and air conditioning. (ASHRAE Guide is the technical reference source.)
Hygrometric Expansion
All materials, particularly those of organic origin, expand and contract in relation to their moisture content, which varies with environment. The Hygrometric Coefficient of Expansion is expressed in "Inches Per Inch Per Percent Of Relative Humidity." Example: gypsum board has a coefficient of 7.2 x 10-6 in. per in. per %rh. This means that with an increase in relative humidity of from 10% to 50%, a gypsum board wall 300 ft. long will have an unrestrained linear expansion of 1.0368" or 1&1/32".
International Conference of Building Officials, a nonprofit organization that publishes the Uniform Building Code.
Impact Insulation Class (IIC)
Single-number rating used to compare and evaluate the performance of floor-ceiling constructions in isolating impact noise. The advantages of this rating system are positive values and the correlation with Sound Transmission Class (STC) values -- both providing approximately equal isolation at a particular value. The IIC rating is used by building agencies for specifying minimum sound-control performance of assemblies in residential construction.
Impact Noise Rating (INR)
Obsolete rating system for floor-ceiling construction in isolating impact noise. INR ratings can be converted to approximate IIC ratings by adding 51 points; however, a variation of 1 or 2 points may occur.
See Noncombustible.
Insulation (Thermal)
Any material that measurably retards heat transfer. There is wide variation in the insulating value of different materials. A material having a low density (weight/volume) will usually be a good thermal insulator.
To estimate untested values that fall between tested values.
International Standards Organization, an organization similar in nature.
One of the finished upright sides of a door or window frame.
Jamb Stud
Wood or metal stud adjacent to the door jamb.
Small beam that supports part of the floor, ceiling or roof of a building.
Joist Hanger
Metal shape formed for hanging on the main beam to provide support for the end of a joist.
Kiln-Dried Lumber
Lumber that has been dried and seasoned with carefully controlled heat in a kiln.
Label Service (UL)
Program allowing a manufacturer to place Underwriters Laboratories Inc. labels on his products that have met UL requirements. A UL representative visits the manufacturing location to obtain samples of the products for testing by UL. In some cases, samples are also purchased on the open market for testing. The public is thereby assured that products bearing the UL label continually meet UL specifications.
Leaks (Sound)
Small openings at electrical boxes and plumbing, cracks around doors, loose-fitting trim and closures all create leaks that allow sound to pass through, reducing the acoustical isolation of a wall, floor or ceiling system.
Ledger Strip
Strip fastened to the bottom edge of a flush girder to help support the floor joists.
Life-Cycle Costing
Selection of the most economical material and systems based on initial costs, maintenance costs and operating costs for the life of the building.
Limiting Height
Maximum height for design and construction of a partition or wall without exceeding the structural capacity or allowable deflection under given design loads.
Horizontal member spanning an opening such as a window or door. Also referred to as a Header.
Live Load
Part of the total load on structural members that is not a permenant part of the structure. May be variable, as in the case of loads contributed by the occupancy, and wind and snow loads.
Force provided by weight, external or environmental sources such as wind, water and temperature, or other sources of energy.
Subjective response to sound pressure, but not linearly related thereto. A sound with twice the pressure is not twice as loud. See Decibel.
Opening with slanted fins (to keep out rain and snow) used to ventilate attics, crawl spaces and wall openings.
Property of a body that resists acceleration and produces the effect of inertia. The weight of a body is the result of the pull of gravity on the body's mass.
Metric Terms
Metric units shown as equivalents in this Handbook are from the International System of Units in use throughout the world, as established by the General Conference of Weights and Measures in 1960. Their use here complies with the Metric Conversion Act of 1975, which committed the United States to a coordinated voluntary conversion to the metric system of measurement. Refer to the Appendix for metric units and conversion factors applicable to subjects covered in this Handbook. For additional information, refer to ASTM E380-76, Standard for Metric Practice.
Joint formed by two pieces of material cut to meet at an angle.
Model Code
Building code, written and published by a building-official association, available to states, counties and municipalities for adoption (for a fee) in lieu of their own, e.g., Uniform Building Code, Standard Building Code, National Building Code.
(1) In architecture, a selected unit of measure used as a basis for building layout; (2) In industrialized housing, a three-dimensional section of a building, factory-built, shipped as a unit and interconnected with other modules to form the complete building. Single-family units factory-built in two halves are usually referred to as "sectionals."
Modulus of Elasticity (E)
Ratio between deformation, a measure of the stiffness of a material.
Moment of Inertia (I)
Calculated numerical relationship (expressed in in.4) of the resistance to bending of a member, a function of the cross-sectional shape and size. A measure of the stiffness of a member based on its shape. Larger moments of inertia indicate greater resistance to bending for a given material.
Moulding (also Molding)
Narrow decorative strip applied to a surface.
Vertical bar or division in a window frame separating two or more panes.
Horizontal bar or division in a window frame separating multiple panes or lights.
Music/Machinery Transmission Class (MTC)
Rating developed by U.S. Gypsum Company to isolate music and machinery/mechanical equipment noise or any sound with a substantial portion of low frequency energy. MTC does not replace Sound Transmission Class (STC) but complements it.
Nail Pop
The protrusion of the nail usually attributed to the shrinkage of or use of improperly cured wood framing.
National Board of Fire Underwriters, now merged into the American Insurance Assn.
National Bureau of Standards, a federal agency.
National Conference of States on Building Codes and Standards, a nonprofit organization formed to increase interstate cooperation and coordinate intergovernmental reforms of building codes.
Neutral Axis
The plane through a member (at the geometric center of the section in symmetrical members) where the fibers are neither under tensile nor compressive stress.
National Fire Protection Assn., an international technical society that disseminates fire prevention, fighting and protection information. NFIPA technical standards include the National Electrical Code which is widely adopted.
National Forest Products Association.
Noise Reduction Coefficient (NRC)
Arithmetic average of sound absorption coefficients at 250, 500, 1000 and 2000 Hz.
Term indicating that the full measurement is not used; usually slightly less than the full net measurement, as with 2" x 4" studs that have an actual size when dry of 1&1/2" x 3&1/2".
Definition excerpted from the ICBO Uniform Building Code: 1. Material of which no part will ignite and burn when subjected to fire. 2. Material having a structural base of noncombustible material as defined, with a surface not over 1/8" thick that has a flame spread rating of 50 or less. The term does not apply to surface finish materials.
Interval between two sounds having a basic frequency ratio of two. The formula is 2n times the frequency, where n is the desired octave interval. The octave band frequency given in sound test results is usually the band center frequency, thus the 1000 Hz octave band encompasses frequencies from 707 Hz to 1414 Hz (n = ± 1/2). The 1000 Hz one-third-octave band encompasses frequencies from 891 Hz to 1122 Hz (n = ± 1/6).
Ohio State University, an independent fire-testing laboratory which is currently inactive.
Parapet Wall
Extension of an exterior wall above and/or through the roof surface.
Penny (d)
Suffix designating the size of nails, such as 6d (penny) nail, originally indicating the price, in English pence, per 100 nails. Does not designate a constant length or size, and will vary by type (e.g., common and box nails).
Performance Specification
States how a building element must perform as opposed to describing equipment, products or systems by name.
A unit of measurement of Water Vapor Permenance (ASTM).
Projecting, square column or stiffener forming part of a wall.
Column supporting a structure.
Pitch of Roof
Slope of the surface, generally expressed in inches of vertical rise per 12" horizontal distance, such as "4-in-12 pitch."
"Top" plate is the horizontal member fastened to the top of the studs or wall on which the rafters, joists or trusses rest; "sole" plate is positioned at bottom of studs or wall.
Floor surface raised above the ground or floor level.
Platform Framing
Technique of framing where walls can be built and tilted-up on a platform floor, and in multi-story construction are erected sequentially from one platform to another. Also known as "Western" framing.
Chamber in which the pressure of the air is higher (as in a forced-air furnace system) than that of the surrounding air. Frequently a description of the space above a suspended ceiling.
Portland Cement
Hydraulic cement produced by pulverizing clinker consisting essentially of hydraulic calcium silicates, usually containing one or more forms of calcium sulfate as an interground addition.
Prescription Specification
Traditional procedure used on building projects to describe by name products, equipment or systems to be used.
Horizontal member in a roof supporting common rafters, such as at the break in a gambrel roof. Also, horizontal structural member perpendicular to main beams in a flat roof.
Forcing out of plumb of structural components, usually by wind, seismic stress or thermal expansion or contraction.
Transfer of heat energy through space by wave motion. Although the radiant energy of heat is transmitted through space, no heat is present until this energy strikes and is absorbed by an object. Not all of the radiant heat energy is absorbed; some is reflected to travel in a new direction until it strikes another object. The amount reflected depends on the nature of the surface that the energy strikes. This fact explains the principle of insulating foil and other similar products that depend on reflection of radiant heat for their insulating value. Radiant heat travels in straight lines in all directions at about the speed of light. In radiant heating systems, heat is often radiated down from the ceiling. As it strikes objects in the room, some is absorbed and some reflected to other objects. The heat that is absorbed warms the object, which, in turn, warms the surrounding air by conduction. This warmed air sets up gentle convection currents that circulate throughout the room.
That member forming the slanting frame of a roof or top chord of a truss. Also known as hip, jack or valley rafter depending on its location and use.
Rafter Tail
That part of a rafter that extends beyond the wall plate -- the overhang.
Reflected Heat
See Radiation.
Reflected Sound
Sound that has struck a surface and "bounced off." Sound reflects at the same angle as light reflects in a mirror; the angle of incidence equals the angle of reflection. Large curved surfaces tend to focus (concave) or diffuse (convex) the sound when reflected. However, when the radius of the reflecting surface is less than the wavelength of the sound, this does not hold true. Thus, a rough textured surface has little effect on diffusion of sound.
Reflective Insulation
Material that reflects and thus retards the flow of radiant heat. The most common type of reflective insulation is aluminum foil. The effectiveness of reflective barriers is diminished by the accumulation of dirt and by surface oxidation.
Persistence of sound after the source stops. When one hears the 10th, 20th, 50th, 100th, etc., reflection of a sound, one hears reverberation.
Reverberation Time
Essentially the number of seconds it takes a loud sound to decay to inaudibility after the source stops. Strictly, the time required for a sound to decay 60 dB in level.
Peak of a roof where the roof surfaces meet at an angle. Also may refer to the framing member that runs along the ridge and supports the rafters.
Measurement in height of an object; the amount it rises. The converse is "fall."
Vertical face of a step supporting the tread in a staircase.
Rough Framing
Structural elements of a building or the process of assembling elements to form a supporting structure where finish appearance is not critical.
Measure of sound absorption of a surface, equivalent to 1 sq. ft. of a perfectly absorptive surface.
Fire stop material in the space between floor slab and curtain wall in multi-story construction.
Safing Off
Installation of fire safety insulation around floor perimeters, between floor slab and spandrel panels. Insulation helps retain integrity of fire resistance ratings.
Southern Building Code Congress International, nonprofit organization that publishes the Standard Building Code.
Small piece or block of wood that bridges several members or provides a connection or fastening between them.
Section Modulus (S)
Numerical relationship, expressed in in.3, of the resistance to stress of a member. It is equal to the moment of inertia divided by the perpendicular distance from the neutral axis to the extremity of the member.
An undesirable condition where the joint finish shows through the surface decoration.
Shaft Wall
Fire-resistant wall that isolates the elevator, stairwell and vertical mechanical chase in high-rise construction. This wall must withstand the fluctuating (positive and negative) air-pressure loads created by elevators or air distribution systems.
Force that tends to slide or rupture one part of a body from another part of the body or from attached objects.
Plywood, gypsum, wood fiber, expanded plastic or composition boards encasing walls, ceilings, floors and roofs of framed buildings. May be structural or non-structural, thermal-insulating or non-insulating, fire-resistant or combustible.
Leading brand of gypsum panel for interior wall and ceiling surfaces, developed and improved by United States Gypsum Company. There is only one SHEETROCK brand Gypsum Panel.
Temporary member placed to support part of a building during construction, repair or alteration; also may support the walls of an excavation.
Horizontal member at the bottom of door or window frames to provide support and closure.
Sill Plate
Horizontal member laid directly on a foundation on which the framework of a building is erected.
Flat (although sometimes ribbed on the underside) reinforced concrete element of a building that provides the base for the floor or roofing materials.
Undersurface of a projection or opening; bottom of a cornice between the fascia board and the outside of the building; underside of a stair, floor or lintel.
Sole Plate
See Plate.
Sound Absorption
Conversion of acoustic or sound energy to another form of energy, usually heat.
Sound Insulation, Isolation
Use of building materials or constructions that will reduce or resist the transmission of sound.
Sound Intensity
Amount of sound power per unit area.
Sound Pressure Level (SPL)
Expressed in decibels, the SPL is 20 times the logarithm to the base 10 of the ratio of the sound pressure to a reference pressure of 20 micropascals. See Decibel.
Sound Transmission Class (STC)
Single-number rating for evaluating the effectiveness of a construction in isolating audible airborne sound transmission across 16 frequencies. Higher numbers indicate more effectiveness. Tested per ASTM E90.
Distance between supports, usually a beam or joist.
Spandrel Beam
Horizontal member, spanning between exterior columns, that supports the floor or roof.
Spandrel Wall
Exterior wall panel, usually between columns, that extends from the window opening on one floor to one on the next floor.
Speed of Sound
Varies with atmospheric pressure and temperature, but is the same at all frequencies. For most architectural work, the speed of sound should be taken as 1,130 ft./second.
Vertical outside member in a piece of mill work, as a door or sash.
Hanger to support the end of the joist at the beam.
Strip of wood fastened to the jambs and head of a door or window frame against which the door or window closes.
Unit deformation in a body that results from stress.
Unit resistance of a body to an outside force that tends to deform the body by tension, compression or shear.
Heavy horizontal timber supporting other members of the frame in a wood or brick structure; a support also for steps.
Structural Clay Facing Tile
Hollow clay units used in bearing and non-bearing walls that have cores exceeding 25 percent of the gross cross sectional area.
Structure-borne Sound
Sound energy imparted directly to and transmitted by solid materials, such as building structures.
Slender structural element that resists compressive forces acting lengthwise.
Vertical load-bearing or non-load bearing framing member.
Rough or structural floor placed directly on the floor joists or beams to which the finished floor is applied. As with resilient flooring, an underlayment may be required between subfloor and finished floor.
Underlying material to which a finish is applied or by which it is supported.
Surface Burning Characteristic
Rating of interior and surface finish material providing indexes for flame spread and smoke developed, based on testing conducted according to TOP ]
Measurement of the intensity (not quantity) of heat. The Fahrenheit (°F) scale places the freezing point of water at 32° and the boiling point at 212°. The Centigrade or Celsius (°C) scale, used by most countries and in scientific work, places the freezing point of water at 0° and the boiling point at 100°. On the Kelvin (K) scale, the unit of measurement equals the Celsius degree and measurement begins at absolute zero 0° (-273°C).
Tensile Strength
Maximum tensile stress that can be developed in a given material under axial tensile loading. Also the measure of a material's ability to withstand stretching.
Force that tends to pull the particles of a body apart.
Thermal Expansion
All materials expand and contract to some extent with changes in temperature. The Thermal Coefficient of Linear Expansion is expressed in "Inches Per Inch Per Degree Fahrenheit." Example: gypsum board has a coefficient of 9.0 x 10-6 in. per in. per °F. This means that with an increase in temperature of 50°, a gypsum board wall 100 ft. in length will have a linear expansion of .54" or an excess of 1/2". The expansion characteristics of some other building materials are more pronounced; a 50° temperature increase would produce expansion in a 100' length of approx. 3/4" in aluminum, 3/8" in steel and 1/2" in concrete.
Thermal Resistance (R)
Resistance of a material or assembly to the flow of heat. It is the reciprocal of the heat transfer coefficient: (1/C, or 1/U)
For insulating purposes, low "C" and "U" values and high "R" values are the most desirable.
Raised member at the floor within the door jamb. Its purpose is to provide a divider between dissimilar flooring materials or serve as a thermal, sound or water barrier.
Through-penetration Fire Stop
A system for sealing through-penetrations in fire-resistant floors, walls and ceilings.
Through-penetration, or "poke-through" openings as they are sometimes called, are holes that penetrate an entire floor or wall assembly to allow the passage of piping, ducts, conduit, cable trays, electrical cables, communications wiring, etc.
Time-Temperature Curve
Rate of rise of temperature in a fire-testing furnace.
Method of fastening two boards together as in a "T" by driving nails into the board that forms the stem of the "T" at an angle so they enter the other board and cross each other.
Tongue-and-Groove Joint
Joint where the projection or "tongue" of one member engages the mating groove of the adjacent member to minimize relative deflection and air infiltration; widely used in sheathing, flooring and paneling. Tongues may be in "V," round or square shapes
Transmission Loss (TL)
Essentially the amount, in decibels, by which sound power is attenuated by passing from one side of a structure to the other. TL is independent of the rooms on each side of the structure and theoretically independent of the area and edge conditions of the structure.
Horizontal plane or surface of a stair step.
Double joists or rafters framing the opening of a stairway well, dormer opening, etc.
Open, lightweight framework of members, usually designed to replace a large beam where spans are great.
U of C
University of California, an independent fire-testing laboratory.
U Value
Coefficient of heat transfer, "U" equals 1 divided by (hence, the reciprocal of) the total of the resistances of the various materials, air spaces and surface air films in an assembly. See Thermal Resistance.
Uniform Building Code -- document promulgated by the International Conference of Building Officials.
Underwriters Laboratories Inc., founded by NBFU, and now operated in affiliation with American Insurance Assn. UL is a not for profit laboratory operated for the purpose of testing devices, systems and materials as to their relation to life, fire and casualty hazard in the interest of public safety.
United States of America Standards Institute, now American National Standards Institute.
Vapor Retarder
Material used to retard the flow of water vapor through walls and other spaces where this vapor may condense at a lower temperature.
Veneer Plaster
Calcined gypsum plaster specially formulated to provide specific workability, strength, hardness and abrasion resistance characteristics when applied in thin coats (1/16" to 3/32" nom.) over veneer gypsum base or other approved base. The term thin coat plaster is sometimes used in reference to veneer plaster.
Wavelength (Sound)
Wave is one complete cycle of sound vibration passing through a medium (such as air) from compression through rarefaction and back to compression again. The physical length of this cycle is termed the wavelength. Wavelengths in air vary from about 1&1/16" for a 20,000-cycle per sec. (see Frequency) sound, to approximately 56&1/2' for a 20-cycle per sec. sound -- the two approximate extremes of human hearing sensitivity. There are waves outside of this range, but generally, they cannot be heard by humans.
Weep Hole
Small aperture at the base of an exterior wall cavity intended to drain out trapped moisture.
Wet Sand
To smooth a finished joint with a small-celled wet sponge. A preferred method to reduce dust created in the dry sanding method.
Warnock Hershey International, an independent fire-testing laboratory.
Window Wall
A type of metal curtain wall composed of metal framing members containing operable sash, fixed lights, ventilators, or opaque glass panels.