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."
[ TOP ]
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.
[ TOP ]
Corner Post
Timber or other member forming the corner
of a frame. May be solid or built-up as a multi-piece member.
[ TOP ]
Cripple
Short stud such
as that used between a door or window header and the top plate.
[ TOP ]
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.
[ TOP ]
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).
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Dead Load
Load on a building element contributed by the weight of the building
materials.
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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.
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Decoupling
Separation of elements to reduce or eliminate
the transfer of sound, heat or physical loads from one element to the other.
[ TOP ]
Deflection
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.
[ TOP ]
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.
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Deformation
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.
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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.
[ TOP ]
Dew Point
The temperature
at which air becomes saturated with moisture and below which condensation occurs.
[ TOP ]
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.
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Double-Hung
Window
Window sash that slides vertically and
is offset in a double track.
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Drip
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.
[ TOP ]
Drywall
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.
[ TOP ]
Exterior Insulation
and Finish System (EIFS)
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.
[ TOP ]
Extrapolate
To project tested values, assuming a continuity
of an established pattern, to obtain values beyond the limit of the test results.
Not necessarily reliable.
[ TOP ]
Factor of
Safety
Ratio of the ultimate unit stress
to the working or allowable stress.
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Fascia Board
Board fastened to the ends of the rafters
or joists forming part of a cornice.
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Fast Track
Method that telescopes or overlaps traditional
design-construction process. Overlapping phases as opposed to sequential phases is
keynote of the concept.
[ TOP ]
Fatigue
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.
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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.
[ TOP ]
Fireproof
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.
[ TOP ]
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.
[ TOP ]
Fire-Resistive
Refers to properties or designs to resist
effects of any fire to which a material or structure may be expected to be subjected.
[ TOP ]
Fire-Retardant
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.
[ TOP ]
Fire Stop
Obstruction in a cavity designed to resist
the passage of flame, sometimes referred to as "fire blocking."
[ TOP ]
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.
[ TOP ]
Fire Wall
Fire-resistant partition extending to
or through the roof of a building to retard spread of fire. See Area Separation Wall.
[ TOP ]
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.
[ TOP ]
Flammable
Capability of a combustible material to
ignite easily, burn intensely or have rapid rate of flame spread.
[ TOP ]
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.
[ TOP ]
Flashing
Strips of metal or waterproof material
used to make joints waterproof, as in the joining of curtain wall
panels.
[ TOP ]
Footing
Lower extremity of a foundation
or loadbearing member that transmits load to load-bearing
substrate.
[ TOP ]
Force
Amount of applied energy to cause motion,
stress
in a body.
[ TOP ]
Foundation
Component that transfers weight of building
and occupants to the earth.
[ TOP ]
Frequency (Sound)
Number of complete vibrations or cycles
or periodic motion per unit of time.
[ TOP ]
Furring
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.
[ TOP ]
Gable
Uppermost portion of the end wall of a
building that comes to a triangular point under a sloping roof.
[ TOP ]
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.
[ TOP ]
Girder
Beam, especially a long, heavy one; the main beam supporting
floor joists or other smaller beams.
[ TOP ]
Gusset
Wood or metal plate
riveted, bolted, glued or pressed (wood trusses) over joints to transfer stresses
between connected members.
[ TOP ]
Heat
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).
[ TOP ]
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.
[ TOP ]
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.
[ TOP ]
Heel of Rafter
Seat cut in a rafter
that rests on the wall plate.
[ TOP ]
Hertz
The units of measure of sound frequency,
named for Heinrich H. Hertz. One Hertz equals one cycle per second.
[ TOP ]
Honeycomb
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.
[ TOP ]
HUD
Housing and Urban Development, federal
agency.
[ TOP ]
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.
[ TOP ]
HVAC
Heating, ventilating and air conditioning.
(ASHRAE Guide is the technical reference source.)
[ TOP ]
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".
[ TOP ]
ICBO
International Conference of Building Officials,
a nonprofit organization that publishes the Uniform Building Code.
[ TOP ]
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.
[ TOP ]
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.
[ TOP ]
Incombustible
See Noncombustible.
[ TOP ]
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.
[ TOP ]
Interpolate
To estimate untested values that fall
between tested values.
[ TOP ]
ISO
International Standards Organization,
an organization similar in nature to TOP
]
Jamb
One of the finished upright sides of a
door or window frame.
[ TOP ]
Jamb Stud
Wood or metal stud
adjacent to the door jamb.
[ TOP ]
Joist
Small beam that
supports part of the floor, ceiling or roof of a building.
[ TOP ]
Joist Hanger
Metal shape formed for hanging on the
main beam to provide support for the end of a joist.
[ TOP ]
Kiln-Dried
Lumber
Lumber that has been dried and seasoned
with carefully controlled heat in a kiln.
[ TOP ]
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.
[ TOP ]
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.
[ TOP ]
Ledger Strip
Strip fastened to the bottom edge of a
flush girder to help support the floor joists.
[ TOP ]
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.
[ TOP ]
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.
[ TOP ]
Lintel
Horizontal member spanning an opening
such as a window or door. Also referred to as a Header.
[ TOP ]
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.
[ TOP ]
Load
Force provided by weight, external or environmental sources
such as wind, water and temperature, or other sources of energy.
[ TOP ]
Loudness
Subjective response to sound pressure,
but not linearly related thereto. A sound with twice the pressure is not twice as
loud. See Decibel.
[ TOP ]
Louver
Opening with slanted fins (to keep out
rain and snow) used to ventilate attics, crawl spaces and wall openings.
[ TOP ]
Mass
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.
[ TOP ]
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.
[ TOP ]
Miter
Joint formed by two pieces of material
cut to meet at an angle. 
