THE ENGINEERING DICTIONARY R O B E R T
S I L M A N
A S S O C I A T E S
THE ENGINEERING DICTIONARY
ASHLAR a square or rectangular cut stone BACK GOUGE the removal of weld and base metal by arc gouging or grinding from the other side of a partially welded joint to assure complete fusion and penetration upon subsequent welding from that side
BACKER ROD an open or closed-cell foam rod (typically polyethylene) used for filling a joint and controlling the depth of the sealant before caulking, see photo; becomes redundant once the sealant has cured
BACKING BRICK relatively low-quality brick used behind face brick or other masonry
BALLOON FRAMING method of wood construction developed in the 1830’s and used in the United States up until the mid-1950’s in the light-frame construction for houses and other similar smaller buidlings; utilizes continuous wall studs that extend from the sill plate of the first story up to the top plate or end rafter of the roof
BALLAST loose stone aggregate (or precast blocks) that protects a roofing membrane from ultraviolet light and physical wear; assists in holding the roof membrane down against wind uplift, and contributes to the fire resistance of the roof covering
BALUSTRADE the entire railing system including top rail, balusters (vertical members between top and bottom rails), and bottom rail
BAND COURSE see belt course BATTERED PILES also known as brace pile or spur pile; a pile driven at an inclination to the vertical to provide resistance to horizontal forces
BATTERED WALL a wall with a sloping back, or front, to withstand hyrdrostatic pressure or other horizontal forces
BATTLEMENT (EMBATTLEMENT) a parapet having a regular alternation of merlons and crenels, see photo
BEDDING COURSE the first layer of mortar at the bottom of a masonry wall BED JOINT see diagram BELT COURSE also called a string course or a band course or a sill course when set at the windowsill level; a band of masonry extending horizontally across the façade or the perimeter of a building; usually projects beyond the face of the building
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THE ENGINEERING DICTIONARY
BIRD’S MOUTH typically a right angled notch cut on the underside of rafter to fit over a beam or the top plate of a stud wall frame, see photo
BLIND HEADER used in multiwythe brick walls to achieve the appearance of an all running bond pattered wall; are angled and the outer wythes of brick are modified to allow for the diagonal placement of the blind header, see photo; can impact (reduce) the composite capacity of the wall assembly, or structural bonding between wythes, compared to full headers
BOLLARD 1. a short vertical post arranged to obstruct the passage of motor vehicles around buildings, sidewalks, or parking lots; 2. ornamental or decorative components on a building façade, see photo
BOND BEAM a course or block embedded in a masonry wall (typically a CMU wall) assembly that provides horizontal stiffness; typically used where a wall would otherwise be braced by the roof or floor structure; consists of CMU blocks that have the upper portions of the webs cut (blocks are typically provided with knock out sections) to allow for the placement of a continuous horizontal rebar and grout; wall reinforcing typically runs continuous up through the cells of the block; wire mesh or fabric is placed in the bed joint below the bond beam course which allows for the bond beam to be grouted solid and not have the grout fall through the ungrouted cells below; the difference between a lintel block and a bond beam block is that the lintel block is U-shaped and the bottom of the block is solid as there is no wall below at openings in the wall BOX BEAM also known as box girder; hollow girder or beam with a square or rectangular cross section; usually refers to cold-formed steel construction but can also apply to hot rolled steel or wood construction too; usually made from two C studs/joists facing toward each other (flange tips pointed toward each other) and a track piece on top and bottom in cold-form steel construction
BUCK ANCHOR piece of steel, typically corrugated, used to laterally tie a brick or stone veneer to the structural back up, see photo
BUILDING BUTTON typically wrought iron tie rods used to brace the masonry facade parallel to the joists in a wood-framed masonry building (i.e. brownstone or row house) against outward buckling by extending through the wall back several joist bays; the outside ends of the ties were kept in place by large cast iron anchor plates on the outer face of the façade, often ornamental shaped as stars, rosettes, or S-shapes; also used on side walls by attaching directly to the ends of the joists bearing in the wall BUTTRESS a pier constructed at right angles to a restraining wall on the side opposite to the restrained material; increases the strength and thrust resistance of a wall
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THE ENGINEERING DICTIONARY
CAISSON 1. type of deep foundation element that consists of a steel shaft that is drilled and socketed into rock and filled with concrete and rebar; 2. a watertight, cylindrical or rectangular chamber used in underwater construction to protect workers from water pressure and soil collapse
CASTELLATED BEAM hot rolled beam cut length wise with a half hexagon pattern; the split halves are then offset and welded back together to form a deeper beam with full hexagonal web openings, see photo CAVITY WALL constructed of a facing (brick, stone, masonry, stucco, rain screen etc.) and a backing wythe that is commonly solid or hollow masonry units (CMU, terra cotta) or stud wall (wood or cold form steel) completely separated by a continuous air space/drainage plane and bonded with metal wall ties or horizontal joint reinforcement; the facing will absorb moisture and slowly drain rainwater or humidity into the wall; the cavity serves as a way to drain the water back out through weep holes at the base of the wall system or above windows
CELLULAR BEAM hot rolled beam cut length wise with a half-circle pattern; the split halves are then offset and welded back together to form a deeper beam with full circular web openings, see photo
CHASE a vertical passage (i.e. penetration through the floor sandwich) for ducts, pipes, or wires in a building CINDER FILL clinker (coal cinder) often placed on top of structural slabs such as reinforced and draped-mesh construction or terra cotta flat arch floor systems; sometimes used as an aggregate, see CINDER CONCRETE
CINDER CONCRETE concrete from the late 1800’s and early 1900’s that used clinker (coal cinder) as a lightweight course aggregate
CLADDING the application of one material over another to provide a skin or layer intended to control the infiltration of weather elements, or for aesthetic purposes (i.e. wood siding, face brick, etc.)
CLIPPED HEADER also known as false header; a bat placed to look like a header for purposes of establishing a pattern
COLLAR JOINT see diagram COLLAR TIE also known as tie beam, tie rafter, or tie joist; the element that ties two rafters together when using a ridge board, to create a side-to-side spanning roof frame instead of an end-to-end spanning ridge beam; rule of thumb is that the collar tie should be in the lower third of the rafters; must be designed for the roof frame thrust and to
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THE ENGINEERING DICTIONARY
span in bending under their own self-weight as well as any other load in the design, such as ceiling loads or attic dead and live loads
COMMON BOND uses a header course repeated at regular intervals, usually every fifth, sixth, or seventh course; the courses use a running bond; headers provide structural bonding between wythes, see diagram
CONTROL JOINT vertical joint made in the wall to allow for shrinkage and prevent cracking
COPING masonry cap on the top of a wall/parapet or pier CORBEL a 'bracket' or block projecting from a wall or column that supports a beam or floor system
CORBELLING a masonry technique of widening or projecting out a masonry wall (or part of a wall) to form a decorative feature, a support shelf, or a ledge for a building element; also used to widen a support wall
CORNICE a molded projection that crowns a wall or divides it horizontally for compositional purposes, see photo
CRENEL any open space between two merlons in a battlement or crenellated parapet, see photo
CUT SHEET specifications, typically for MEP equipment, that lists the size and weight of a piece of equipment
DAVIT a structure, usually made of steel, which is used to lower things over an edge of a long drop-off, such as lowering a maintenance trapeze down a building, see photo a buried plate, wall, or block attached at some distance from and forming an anchorage for a retaining wall
DEADMAN
DRAPED-MESH CINDER-CONRETE SLABS light weight floor system developed in the late 1800’s and early 1900’s where the cinder concrete slab serves only to provide a flat, stable surface for use and to transmit the applied loads to the drapedmesh reinforcing that alone spans the beam-to-beam gap; all applied loads are resisted by the catenary action of the draped-mesh, see diagram; see CINDER CONCRETE
DRIP STONE a projecting brick or molding to allow water to run-off away from the wall, or a projecting unit with a slot cut on the underside of the projection to stop the momentum of the water or surface tension
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THE ENGINEERING DICTIONARY
DUNNAGE a configuration of members that forms a structural support for a cooling tower or similar appendage to a building but is not part of the building itself; usually located on the roof of buildings and projects above the roof to elevate the MEP unit it supports above the roof surface for maintenance purposes, see photo
DUTCHMAN a piece of similar material used to replace a damaged or missing portion of natural stone, a masonry unit, or piece of wood; a symmetrical cut in the unit is made to fit exactly the shape and size of the Dutchman allowing the smallest possible void for the installation of the mortar, epoxy, or wood glue; a successful Dutchman should be structurally sound and blend with the repaired unit.
EFFLORESCENCE whitish haze of slat crystallization found on brick, concrete, or stone masonry; generally caused by excessive ‘pulling’ of soluble salts into the masonry and out through the surface; typically caused by carbonates from lime mortar or sulfates deposited on the masonry surface from air-borne or water-deposited pollutants in the atmosphere, see photo
ENGLISH BOND made up of alternate courses of headers and stretchers, with headers centered on stretchers, see diagram
EXPANSION JOINT a joint or gap between adjacent parts of a building structure or different materials that have different thermal expansion rates (see control joint for material movement due to a different cause)
EXTRADOS exterior curve or boundary of the visible face of an arch FAÇADE ORDINANCE LAWS a law passed by local authorities requiring the periodic inspection of certain building facades (typically more than 6 stories tall) by a licensed engineer or architect, to help ensure public safety; refer to Local Law 11/98 in New York City
FIRE BRICK brick made of fire-resistant clay; used to line the firebox are of a fireplace
FIRE CUT JOISTS also known as fireman's cut; a diagonal cut at the end of a joist where it enters a masonry wall; if the joist burns through somewhere along its length, damage to the wall is prevented as the fire cut allows the joist to fail and leave the masonry wall standing without prying up the brick above, see diagram; the fire cut was often combined with a small-gage metal strap embedded in the masonry to restore the torsional stability of the joist that had been lost due to the removal of the top portion of the joist end
FIRE STONE any stone, such as sandstone, that is fire resistant and suitable for use in firplaces
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THE ENGINEERING DICTIONARY
FLEMISH BOND alternates stretchers and headers in each course with headers centered over stretchers in the course below, see diagram a composite beam, typically comprised of a steel plate sandwiched between two wood members and thru-bolted together, see TeKI
FLITCH BEAM
FOOTER contractor speak for a footing “FULL PEN” and abbreviation for a full penetration weld; weld metal extends through the complete thickness of the parts being joined
FURRING wood or metal strips fastened to the inside of a masonry wall or top or bottom of a concrete slab as a base for interior finishes
GARGOYLE an ornamental spout to discharge water outward from behind parapets; typically a carved or molded ornamentation in the form of a grotesque figure (note that if it does not discharge water it is only call a grotesque, not a gargoyle)
GUASTAVINO TILE ARCH method devised by Rafael Guastavino of constructing floors and domes, often long-span, by means of thin tiles; the tiles were typically 1” thick, 6” wide, and from 12” to 24” long and bonded together in Portland-cement mortar so as to make one solid mass, see photo, see TeKI
GOVERNMENT ANCHOR an attachment to the end of a beam before it is set in a beam pocket in a masonry or concrete wall to keep it from pulling out and assist the floor diaphragm in bracing the wall; see our typical detail beam bearing on new or existing masonry wall
GRILLAGE BEAM a beam used like a bearing plate to distribute large reaction loads to a wall, floor, or soil; usually steel wide flange beams or cast-in-place reinforced concrete, see photo
HEADER (FRAMING) a framing member perpendicular to the span of floor joists or roof rafters that supports or heads off joists or rafters at an opening in a floor or roof; the framing member spanning over a door or window opening in wood construction
HEADER (MASONRY) see diagram HEADER COURSE also known as row lock, see diagram HEAD JOINT see diagram HELLDOG also known as a rivet buster; a demolition tool used to remove rivets by busting the rivet heads off and driving the rivet shaft out of the hole.
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THE ENGINEERING DICTIONARY
HILTI BOLT contractor speak for a post installed anchor (expansion or epoxy) made by the manufacturer HILTI
HIP BEAM see hip rafter HIP RAFTER a diagonal rafter extending from the top plate of the wall to the roof ridge
INTRADOS the inner curve of the visible face of an arch JOINTING also known as tooling; finishing of masonry joints; a metal jointer is used to smooth down and remove mortar to achieve a desired joint finish; see diagram for different types of mortar joints KICKER a supplementary brace installed at an angle that stiffens a wall, post, or beam; often used to prevent torsion on beams when horizontal forces are applied to the bottom flange of a beam.
LEDGER typically a single or multiple ply wood beam or steel angle attached to a wall and used to support floor or roof structure; usually attached to new wall construction with thru-bolts or existing walls with post-installed anchors at a staggered spacing, see photo
LIFT height of grout, mortar, or concrete placed at one time from one pour or application
LINTEL a structural element (i.e. steel channel, steel angle, steel wide flange beam, stone block, wood beam, etc.) that spans an opening in a masonry wall and supports wall and floor load above
MERLON forms the vertical solids of a battlement or crenellated parapet, see photo MUNTIN see sash bar NEEDLE BEAM a temporary shoring beam used to create new openings in an existing wall (see needling), see photo & typical details
NEEDLING the act of creating new openings in existing load bearing walls (typically masonry walls) by cutting or chipping a series of small holes, at the location of the new opening, to receive temporary shoring beams or needle beams that are placed perpendicular to the wall and jacked and shimmed tight to fully engage the wall above; the new opening is then created below and new lintels and or columns are placed below, see photo & typical details; needling is often a means and methods issue and should be designed by a licensed engineer hired by the contractor
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THE ENGINEERING DICTIONARY
PARTY WALL also known as a common wall; a wall used jointly by two parties under easement agreement, erected upon a line dividing two parcels of land, each of which is a separate real estate entity
PERCHED WATER TABLE can also be referred to as perched water; pockets of ground water trapped in a layer of impermeable soil or rock above the normal groundwater table in a given area
PILE type of deep foundation; a long heavy timber, steel, or reinforced concrete column that has been drilled, driven, jacked, jetted or cast vertically into the ground; transmits a column or wall load, distributed through a reinforced concrete pile cap, to a strong soil layer or bedrock below grade; usually located in closely spaced groups depending on the magnitude of supported load and connected by a pile cap, see photo PLATFORM FRAMING also known as ‘stick framing’ or ‘stick construction’; typically refers to the most common method of light-framed construction for houses and small apartment or commercial buildings; refers to the sequence of construction where the first floor framing is constructed atop the foundation, the first story walls (sill plate, studs, top plate) are then built on top of that floor framing below, the next floor framing, or platform, is then built atop of walls below and this sequence continuing to the top floor or roof; the plat form framed wall, in contrast to the balloon framed wall, is independent for each floor
PLINTH a continuous, usually projecting course of stones forming the base or foundation of a wall
POINTING refilling of existing deteriorated masonry mortar joints that have been raked out and cleaned with new mortar
Q-DECK contractor speak for metal deck, see TeKI QUOIN 1. exterior corner of a masonry wall; 2. one of the stones or bricks forming the corner of a masonry wall; usually differentiated from adjoining surfaces by material, texture, color, size or projection
RIM BOARD 2x sawn lumber or engineered wood (same depth as joists) at the end of floor joists that fills the space between the sill plate and the bottom wall plate, or between the top plate and bottom plate in a multi-story construction; also can be used to stabilize the end of joists
RUNNING BOND uses only stretcher courses with head joints centered over stretchers in the course below, see diagram
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THE ENGINEERING DICTIONARY
RUN OFF-TABS a scrap piece of base metal tacked onto the end of the main piece of base metal that allows the welder to end the weld without compromising the weld capacity by continuing the weld passed the end of the main piece of base metal; used in the arc-welding process
RUST JACKING the displacement of building elements due to the expansion of iron and steel elements as the metal rusts and becomes iron oxide; common in masonry buildings constructed in the early twentieth century that used skeletal steel embedded in brick masonry
SAILOR see diagram SASH BAR also known as a glazing bar, muntin, or window bar; one of the strips of wood or metal that separates the panes of glass in a window
SCARF JOINT a joint made by the cutting of overlapping mating parts so that the joint is not enlarged and the patterns are complementary, and securing them by glue, fasteners, welding, or other joining method, see photo
SECANT PILE a type of pile that forms a secant foundation wall that consists of alternating primary piles and secondary piles; primary piles are reinforced with steel wide flange beams or steel rebar and are installed first with the secondary piles installed in between and typically overlapping the primary piles by a designed dimension; secondary piles are often installed while the primary piles' concrete is still fresh, to form the connection; in contrast, a tangent pile wall is constructed with no overlap; the advantage to secant or tangent pile foundation walls, as opposed to conventional foundation walls, is that the wall can be installed from above prior to major excavation on the site
SHIM a shim is a thin and often tapered or wedged piece of material, used to fill small gaps or spaces between objects; typically used in order to support, adjust for better fit, or provide a level surface
SHINER see diagram SIDEWALK VAULT space or room below a sidewalk directly adjacent to a building cellar or basement covered with a structural slab and sidewalk topping slab or stone slabs; traditionally slabs span to steel beams
SILL COURSE see belt course SISTER a new wood joist attached directly to an existing wood joist with thru-bolts at a staggered spacing to reinforce the existing joist for stress and/or deflection; the term “sister� can also apply to cold-formed steel, hot-rolled steel, or concrete construction
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THE ENGINEERING DICTIONARY
SLEEPERS strips of wood, typically attached to the top of concrete slabs, used to create space for ventilation or leveling purposes and supports a wood floor
SLURRY WALL a technique used to build reinforced concrete walls in areas of soft earth close to open water or with a high ground water table
SOLDIER BRICK/COURSE a course of bricks laid on their ends so that only their long sides are visible, see diagram
SOLDIER PILE steel wide flange or pipe piles installed vertically into the existing ground to provide either temporary or permanent shoring for a vertical excavation; are set at a designed spacing with planking spanning horizontally between the soldiers to retain the soil; walers and/or rakers brace the soldiers as needed SOUNDING a rudimentary approach in which a common hammer is used to strike the surface of concrete; hollow or dull tones that can be heard and recognized by the inspector indicate the existence of relatively shallow delamination’s in the structure; can also be useful for locating areas of severe damage to the cement matrix that can correspond to reduced strength SPALL a fragment or chip that has fallen from a masonry or concrete surface by rusting of the rebar, encased steel beams or columns, or by action of the elements, see photo
SPANDREL BEAM any beam spanning between columns on the perimeter of a building (typically steel or concrete construction)
SPLAY slanted or beveled surface SPRING OF ARCH point at which an arch, vault, or dome rises from its support STACK BOND provides no interlocking between adjacent masonry units and is used for its architectural effect; horizontal reinforcement should be used with stack bond to provide lateral bonding, see diagram
STAINLESS STEEL 304 A light-duty stainless steel STAINLESS STEEL 316 A marine grade or heavy-duty stainless steel (See stainless steel teki for extreme applications) STRAP BEAM a concrete beam that connects or ties two footings together to eliminate eccentricity in one or both of the footings and accomplish a more uniform distribution of bearing pressure
STRETCHER see diagram ROBERT SILMAN ASSOCIATES
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THE ENGINEERING DICTIONARY
STRINGER an inclined member supporting the treads and risers of a staircase STRING COURSE see belt course SUGARING the deterioration or disintegration of stone caused by the breaking up or dissolving of the stone surface
TERRA-COTTA FLAT ARCH developed in the late 1800’s and early 1900’s as means of constructing a “light weight” noncombustible floor system; comprised of hollow trapezoidal terra-cotta blocks that span between the bottom flanges of the floor beams with the block in the middle of the span in the traditional keystone shape; typically the blocks are approximately the same depth of the floor beams and the bottom of the blocks extend several inches below the bottom flanges; the blocks can either be laid with the webs parallel to the beam in the Side Method or laid end to end to form a series of continuous webs from beam to beam in the End Method; loose cinder fill or cinder concrete was placed on top of the arches and beams to create a level floor, see figure TOOLING also known as jointing; compressing, shaping, or finishing of mortar joints with a special finishing tool
TOOTHING an arrangement of bricks alternately projecting at the end of a wall to permit bonding into a later continuation of the wall; commonly describes the detail at infills or repairs of masonry walls, whereby the new and existing masonry are arranged to key into each other at alternating or intermediate courses
TRIMMER supports the header at an opening and typically frames out the extent of the opening in a floor or roof; typically parallel to the joist or rafter span
UNDERPINNING the full width extension of an existing building foundation to a lower elevation to accommodate a new architectural design (typical reason in NYC) that calls for the excavation or lowering of a level directly adjacent to an existing foundation that would otherwise be undermined; sections of soil or rock are excavated by hand, or machine were possible, and new concrete is poured underneath the existing foundation sequentially in a strategic order designed by a geotechnical consultant; essentially creates a new foundation below an existing foundation; can be executed in isolated or localized areas of a building as well as to an entire building foundation if necessary; see photo and typical detail, see photo & typical detail; typically a means and methods issue and should be designed by the geotechnical engineer for the project or a licensed engineer hired by the contractor UNREINFORCED MASONRY (URM) BEARING WALL CONSTRUCTION load bearing masonry wall that supports its own weight as well as portions of the building’s floor and roof load; acts as the structure’s main force resisting system under
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lateral loads; typically were not engineered but designed empirically based on tables published in local building laws
“UT� ultrasonic testing, used to ensure a weld does not have any defects, typically used for full or partial penetration welds
VITRINE a glass-paneled cabinet or case for displaying articles such as china, objects art, or fine merchandise
VOUSSOIRS any of the wedge-shaped units in a masonry arch, having side cuts converging at one of the arch centers
WALKING COLUMN a concrete column where the centerline of the column above is offset from the centerline of the column below; the offsetting, or stepping, typically occurs at a floor level and the transition occurs over a minimum of three floors where the depth of the middle column is equal to the depth of the column below plus the additional offset dimension of the column above
WATER TABLE a projecting masonry stringcourse, molding, or ledge placed so as to divert rainwater from a building
WEEP HOLE openings in masonry joints left at the base of a masonry wall so moisture can escape
WET WALL contractor speak for a wall that has water pipes running through it, typically a wall between bathrooms
WALER horizontal bracing beam, typically used in the temporary shoring and bracing of excavation sheeting, new foundation walls, or existing masonry walls; typically spans to diagonal rakers or return walls for lateral support, see photo
WYTHE see diagram
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