Glossary of Terms
Glossary of Terms
A B C D E F G H I J K L M N O P Q R S T U V W X Y ZA
ACI - American Concrete Institute. Active pressure - In soil mechanics, the pressure which would cause a wall to move away from the soil. For example, the pressure applied on a retaining wall by the retained soil. Admixture - A chemical or mineral added to a concrete mix before or during mixing to improve or change qualities such as setting time, air entrainment, workability, etc. Aggregate - In concrete construction, an inert material such as sand and gravel combined with Portland Cement and water to make concrete. Aggregates are divided into course (gravel) and fine (sand), depending upon whether or not they pass thru a no. 4 sieve. AISC - American Institute of Steel Construction. AITC - American Institute of Timber Construction. Allowable Stress Design (ASD)- Defined by ASCE-7, Minimum Design Loads for Buildings and Other Structures: as "A method of proportioning structural members such that elastically computed stresses produced in the members by nominal loads do not exceed specified allowable stresses (also called working stress design)". This design method compares allowable stress to actual stress. ASCE - American Society of Civil Engineers. APA - The American Plywood Association, now known as the Engineered Wood Association. ASHRAE - American Society of Heating, Refrigerating and Air-Conditioning Engineers. ASTM - ASTM International, originally known as the American Society for Testing and Materials. AWPA - American Wood Protection Association. Axial load - A load applied parallel with and along a member's longitudinal axis. A typical column experiences axial load. An axial load may be either compressive (squeezing) or tensile (stretching).B
Base plate - A plate, usually square or rectangular steel, fastened to the bottom of a column or post. Base plates are supported by a foundation or other structural component, to which they are usually secured with anchor bolts. Batter pile - A pile inclined from vertical. Beam - A horizontal structural element used to support joists, trusses, walls, or other structural elements. Bell - An enlarged portion at the bottom of a pile or pier. Bending Bentonite - A volcanic clay that undergoes large changes in volume with changes in moisture content. Bleed water - In concrete construction, the water that rises to the surface of recently placed concrete. Board foot - A volume measure of rough sawn lumber equal to 1 foot length x 1 foot width x 1 inch depth (1/12 cubic foot). Bond beam - A masonry beam placed on top of (or at regular vertical intervals within) a CMU wall. Composed of grouted horizontal steel reinforcing bars placed within shaped CMU blocks. A photo of a partially grouted bond beam is found here. Bonding agent - In concrete construction, usually a liquid applied material used to assist the bond between new and existing concrete. Bottom plate - The bottom horizontal member of a framed wall. Bottom plates are usually single member, and may use pressure treated wood, depending upon their location and exposure. British thermal unit (BTU) - The amount of heat required to raise the temperature of one lbm of water by 1 degree Fahrenheit. Built-up roofing (BUR)- Also called 'tar and gravel'. Roofing made up of alternating layers of bitumen and reinforcing fabric often topped with gravel or other aggregate.C
Cantilever - Refers to a slab, beam, or other structural member with a projected, unsupported end. Cantilevered beams and slabs experience tension in the upper cross sectional area, requiring reinforcement steel at this area. Cavity - A term used in CMU construction to describe the holes in the CMU blocks. Cavity cap - A screen or other material placed in the CMU course immediately below a bond beam or tie beam within a CMU wall. Cavity caps prevent the grout or concrete from flowing into the CMU cavities below the beam. The caps should not be allowed to interfere with bond between the CMU courses (in the case of a bond beam) or between the bottom of a tie beam and adjacent CMU. Cement (Portland) - The binder in concrete. Portland Cement is a fine powder, usually gray in color. It undergoes a chemical process called hydration in the presence of water, whereby it hardens and binds course and fine aggregates together to form concrete. Cleanout - In CMU construction, a hole at the bottom of a CMU wall under construction used to remove, or 'clean out', loose mortar and other debris. Cleanouts are placed at the bottom of vertical reinforcement steel bars, located in 'filled cells' within the CMU wall. A photograph of CMU clean outs may be found here; a pipe through which a snake can be pushed to unclog a sewer. CMU - Concrete masonry unit, or 'block' masonry. Collar tie - A horizontal roof framing member sometimes used to connect the upper third of two opposing roof rafters. Colloid - A tiny particle (1-500 millimicrons) which causes turbidity in water because it does not settle quickly. Compaction - Densification of soil by mechanical equipment such as jumping jacks, plate compactors, etc. Components and Cladding (C&C) - Defined by ASCE-7, Minimum Design Loads for Buildings and Other Structures as "Elements of the building envelope that do not qualify as part of the main wind force-resisting system". A smaller C&C area generally results in higher wind pressure. Compression member - A member which primarily experiences compression forces, or 'squeezing'. Columns and posts are typical compression members. Concrete - A mixture of Porland Cement, course and fine aggregates, and water. Concrete, normal weight - Concrete (using normal weight aggregate) which weighs approximately 150 lbf per cubic foot when cured. Concrete, plain - Concrete that is not reinforced with steel. Concrete, structural lightweight - Concrete that uses lightweight aggregates to reduce the concrete's weight. Consolidation - Densification of soil, sometimes related to the expulsion or drainage of excess water. Cover - In concrete construction, a term used to describe the distance between embedded reinforcing steel and the surface of the concrete. Sometimes referred to as 'clear cover', it is an important with regard to steel corrosion protection and steel development. Crazing - In concrete construction, a network of fine random cracks on the concrete surface. Crazing is the result of surface layer shrinkage often related to improper curing or placement techniques. Creep (concrete) - Long term deflection or deformation of a structural member under a sustained load. CRI - The Carpet and Rug Institute. Cricket - A built up ridge between two adjoining roof slopes or above a slope/vertical interface. A crickets prevents a non-sloped roof condition. Cripple - In framing, short vertical members placed at regular intervals above a door or above/below a window opening. Crown - In wood framing, the natural curve of sawn lumber board. When the studs of a framed wall are laid out during construction, they are 'crowned' so that the dominant curve of all studs points in the same direction. The goal is to increase the flatness of the wall. CTIOA - Ceramic Tile Institute of America. Curing - The process by which freshly placed concrete is maintained in optimal temperature and moisture conditions in order to promote proper hydration.D
Dead Load - The weight of the structure itself and other permanently supported, inactive materials and attachments. Deflection - Movement of a structural member. Development length - Defined by ACI 318 Building Code Requirements for Structural Concrete as: "Length of embedded reinforcement required to develop the design strength of reinforcement at a critical section". Diaphragm - A floor, ceiling, roof or other structure orientated on a horizontal plane which transfers horizontal loads to shear walls usually orientated parallel with the direction of load. Distributed load - A load applied over a linear distance (lbf per foot) or area (lbf per square foot). Double shear - A loading condition where shear is applied at two locations on a connecting bolt. Dowel - A round cylindrical rod. Wood dowels are used as connectors in timber construction. Also used to describe a length of reinforcement steel epoxied into concrete. Dressed lumber - Sawn lumber that is planed on all four sides, as opposed to 'rough sawn' lumber. Dressed lumber has smaller dimensions than the nominal size. For example, a dressed 2x4 is actually 1-1/2" x 3-1/2" in size. Drywall Finishing Council Durowall - A brand name sometimes used as a generic term for horizontal joint reinforcement used in masonry construction. This type of reinforcement is relatively small in diameter (3/16" typical), and is embedded in the horizontal joint mortar between block courses. It is generally used for crack control but may also be used for structural considerations.E
Enclosed building - In wind loading analysis, a term used to define a building that is not 'partially enclosed' or 'open'. These terms are defined below. Engineer of Record - Defined by Florida Administrative Code as: "A Florida professional engineer who is in responsible charge for the preparation, signing, dating, sealing and issuing of any engineering document(s) for any engineering service or creative work." Escarpment - A steep cliff or slope.F
Fascia - A board or other material secured to rafter or truss ends around the exterior perimeter of a roof. Filled cell - In CMU wall construction, a vertical steel reinforcing bar which is commonly placed at corners, at both sides of window and door openings, and at regular intervals along the length of a wall. The steel is placed inside the CMU block cavities and grouted. Fines - Clay and silt sized particles. Fish mouth - A point of unsealed lap at rolled membrane roofing. Fish mouths may result from inadequate asphalt or sealant at the membrane laps or uneven roll-out due to improper storage of the membrane roll. In a hot-mopped membrane application, they can also result from the asphalt being allowed to cool prior to the installation of the lapped membrane. Fixed - A term sometimes used to describe the support condition of a beam, column, or other structural member. A support is 'fixed' if it is restrained from horizontal, vertical, and bending movement. Flange - The top and bottom, horizontally orientated portions of an 'I' shaped structural steel member. Flashing - A strip of metal or other material used to stop water from penetrating an interface between a wall and roof, two roof slopes (valley), or around a roof penetration. Float - In construction management, the amount of time that an activity can be delayed without delaying any succeeding activities. Flush - A term used in construction to define aligning surfaces. For example, the top of a screw driven 'flush' would be at the same level (not embedded or protruding) as the surrounding material. Footing or foundation Freeze (in piles) - A large increase in the ultimate capacity (an required driving energy) of a pile after it has been driven some distance. FSEA - Florida Structural Engineers Association. Furring (strips) - Long thin strips of material (often wood) used to build out, surface level, or provide a fastening base in wall or ceiling construction. For example, 1x2 pressure treated furring strips, placed vertically at regular intervals, are often secured to the interior face of a CMU wall in preparation for drywall.G
GA - The Gypsum Association Gable - A triangular shaped area of exterior wall at the end of a roof. Gables are often found at the end of a home or other building. Gables are susceptible to structural failure due to significant wind events if not constructed or braced properly. Galvanized - A zinc coating on a ferrous metal fastener intended to prevent corrosion. Gap graded - A soil with a discontinuous range of particle sizes. Girder truss - A prefabricated wood truss used to support other trusses. Depending on the loading conditions, larger member sizes or multiple plies may be used. Glazing - A term often used to describte window glass in larger buildings. Glulam - From the APA - Engineered Wood Association website: "Glulam is composed of individual wood laminations, or 'lams', specifically selected and positioned in the timber, based on their performance characteristics, and bonded together with durable, moisture-resistant adhesives. Glulam is available in depths from 6 to 72 inches or greater and in lengths up to 100 feet and longer." The layers are visible at the sides of a typically installed glulam. GPR - Ground Penetrating Radar. A geotechnical investigation tool which uses radar pulses to obtain information on subsurface conditions. GPR is sometimes used as part of a sinkhole investigation. Grade beam Gradient - A change per unit distance. Grain - A mass unit equal to 0.000142857 lbm. Grillage - A footing or part of a footing composed of horizontally laid timbers or steel beams. Grout - A mixture of Portland Cement, fine aggregates, and water. Some common uses for grout include filling CMU cavities around vertical reinforcement steel; providing a full contact bearing surface between a column base plate and a footing, and filling gaps such as those between floor tiles. Gusset plate - In wood truss manufacturing, a perforated metal plate pressed into the joint between two structural elements, such as a web and top or bottom chord.H
Header - A structural member over a door, window, or other wall opening. This term is sometimes used interchangeably with lintel or beam. 'Header' is more often used in wood framing where 'lintel' is often used to describe a steel or CMU member. Heat of hydration - The exothermic heat given off by concrete as it cures. Hip - A type of roof where the slopes terminate at a level roof edge around the perimeter exterior walls or other supports. Honeycomb - In concrete construction, a term sometimes used to describe the problem of voids or empty spaces within cured concrete. Honeycomb may be hidden within the concrete but is often exposed along the edge of a slab or other concrete structure when the forms are removed. It is the result of improper consolidation during concrete placement. Closely spaced reinforcement steel and low concrete slump are two factors which may increase the probability of occurrence. Hydration - In concrete construction, the chemical reaction between Portland Cement and water by which the cement, water and aggregates become hardened concrete. HVHZ - High Velocity Hurricane Zone. Includes Miami-Dade and Broward Counties only.I
In situ - In original location; without removal; in place.J
J bolt - A steel bolt in the shape of a 'J' or 'L' embedded in concrete or grouted CMU. Usually accepts a threaded nut and washer at the protruding end. Used for securing column base plates, ledgers, etc. Jack - In framing, a shorter stud placed at either side of a door or window opening supporting a header or other horizontal framing member. Jack truss - A small roof truss used where the overall depth of the roof structure is reduced such as near hip roof edges. Jamb - The vertical framing member located at the side of a window or door opening. Jig - A device used to hold a tool or piece of material in a certain position during construction. Joist - A horizontal roof or floor structural support member, usually spaced at regular intervals.K
Key - In concrete construction, a notch in an existing concrete surface against which new concrete is placed. The notch helps prevent differential movement between the old and new concrete through shear in the key. King stud - In wood framing, a full length stud placed adjacent a jack, used in forming a window or door opening. Kip - 1000 lbf. For example, 3 kips is 3000 lbf. Knee brace - A diagonal brace between a vertical and horizontal element. Knee braces may be used to provide lateral stability or support vertical loads. Ksi - 1000 lbf per square inch. For example, 3 ksi is equivalent to 3000 lbf applied over 1 square inch.L
Lag screw - Also called 'lag bolt'. A large wood screw. Lead holes of 40% to 85% of the shank diameter are required for lag screws with larger diameters. The appropriate lead hole size depends upon the specific gravity, or density of the wood; larger lead holes are required for denser wood. Lagging - Heavy planking used to construct walls in braced cuts and excavations. Lateral Force Resisting System - The components within a structure that resist overturning or horizontally applied loads such as wind, earth, or water. Typically includes shear walls, diaphragms, bracing, etc. Lath - A thin, narrow strip of wood or metal used for lath and plaster method of finishing interior walls. This method has been largely replaced by the use of drywall. Lath may also refer to the mesh used to reinforce plaster, stucco, or mortar. lb-ft - A unit measurement of moment (or bending), in units of force multiplied by distance. For example, 1 lbf applied at a distance of 3 feet would result in a moment of 3 lb-ft. lbf - A unit force measurement of lbm in earth's gravity. lbm - A unit mass measurement. Ledger - A horizontal member secured to a wall or other vertical surface used to support a roof, floor, or other structure. Lintel - A structural member over a door, window, or other wall opening. This term is sometimes used interchangeably with header or beam. 'Lintel' is more often used in CMU construction where 'header' is often used to describe a wood member. Live load - The weight of all temporary objects in a structure such as people, furniture, or other temporary loads brought about by the normal use and occupancy of a structure. Live loads do not include construction or environmental loads such as wind. Load and Resistance Factor Design (LRFD) - A method of proportioning structural members using load (greater than 1) and resistance (less than 1) factors so that member strengths are not exceeded when the structure is subjected to all design loads. This design method compares actual strength to required strength. Load factor - Defined by ASCE-7, Minimum Design Loads for Buildings and Other Structures as: "A factor that accounts for deviations of the actual load from the nominal load, for uncertainties in the analysis that transforms the load into a load effect, and for the probability that more than one extreme load will occur simultaneously". LVL - Laminated Veneer Lumber, or an engineered wood product that uses several layers (veneers) of thin wood adhered together to form a structural member. The layers are visible at the bottom of a typically installed LVL.M
Main Wind Force Resisting System - Defined by the ASCE-7, Minimum Design Loads for Buildings and Other Structures as "An assemblage of major structural elements assigned to provide support and stability for the overall structure. The system generally receives wind loading from more than one surface." Examples include shear walls, diaphragms, rigid frames, etc. Modulus of elasticity - A measurement of the stiffness of a material determined by the ratio of tensile stress to tensile strain within the elastic (linear) portion of the stress-strain curve. Moment (or bending) Moment connection - A connection designed to transfer moment as well as other forces between the connected members. Mud line - The lower surface of a braced cut or excavation. 'Mud line' is also used to describe the underwater point at which the soil at the bottom of a canal or other body of water meets an adjacent seawall.N
Node - A term used in truss design and analysis to describe a point at which webs and chords meet and loads may be applied; in construction management, 'node' is used to describe an activity in the critical path diagram. Nominal load - The magnitude of the loads specified by the applicable codes and standards. Normally consolidated soil - Soil that has never been consolidated by a larger stress than is presently existing. NAIMA - North American Insulation Manufacturers Association. NCMA - National Concrete Masonry Association. NRCA - National Roofing Contractors Association.O
Open building - Defined by ASCE-7, Minimum Design Loads for Buildings and Other Structures as: "a building having each wall at least 80% open". Open web steel joist - Also called a 'bar joist'. A truss composed of steel bar webs welded to horizontal steel angles which form the top and bottom chords. Outlooker - A structural member used to extend a roof overhang over the side of a building. Outlookers are usually placed at regular intervals and orientated perpendicular to the main roof joists or trusses. They are commonly installed over a gable end with the gable end wall elevation dropped enough to accomodate the depth of the outlookers.P
Parapet (wall) - A vertical wall or extension rising above the roof. Partially enclosed building - Defined by ASCE-7, Minimum Design Loads for Buildings and Other Structures as: "a building which complies with both of the following conditions:1. The total area of openings in a wall that receives positive external pressure exceeds the sum of the areas of openings in the balance of the building envelope (walls and roof) by more than 10%, and
2. The total area of openings in a wall that receives positive external pressure exceeds 4 ft2 (0.37 m2) or 1% of the area of that wall, whichever is smaller, and the percentage of openings in the balance of the building envelope does not exceed 20%."
Passive Pressure - A pressure which counteracts active pressure. For example, the pressure applied on a retaining wall by the soil located opposite the retained soil. Perm - A rating of water transmission through a material. In the U.S., a perm is defined as 1 grain of water vapor per hour, per square foot, per inch of mercury. (1 lb = 7000 grains; 1 inch of mercury = 0.49 psi) Pilot hole - Also called a 'lead hole'. A drilled hole made in preparation for a larger drill bit or fastener such as a lag screw. Pinned connection - A term used to describe the condition of no moment restraint at the support or connection of a beam, column, or other structural member. Pitch - The slope of a member or roof typically given as a ratio of rise to run (vertical to horizontal). Roof pitches are often expressed as the rise that occurs over every 12 inches of run. A roof pitch of '5:12' indicates 5 vertical change occurs over every 12 horizontal change. Plumb - The state of a component being straight up and down, or precisely perpendicular to level. Point load - A load applied at one point, such as that experienced by a wall supporting a beam. Also called a concentrated load. Ponding - Standing water at low areas of a roof. Powder Actuated Fastener (PAF) - A fastening method which uses a controlled explosion from a chemical propellant, similar to a firearm, to drive a steel fastener. PT - Pressure treated. Discussed further here. Purlin - A horizontal member sometimes used to support a roof deck. Transfers roof loads to the primary framing members.