Accessory A supplementary building product such as doors, windows, skylights, vents, gutter, flashings, etc.
Alloy A metallic substance composed of two or more chemical elements, at least one of which is a metal.
Aluminium-zinc alloy coating Aluminum zinc alloy (55 % aluminum, 43.4 % zinc and 1.6% silicon) coated steel. The aluminum zinc alloy is applied by the continuous hot dip method also referred to as ZINCALUME or GALVALUME.
Annealing To soften a metal by heating, to restore or increase its ductility.
Anti-capillary groove (ACG) An indentation formed in the edge of a metal cladding profile or flashing to prevent capillary action.
Apron flashing A near horizontal flashing with a vertical up stand that prevents ingress of or sheds water from a higher wall or roof onto a lower roof.
AS Australian Standard. Generally used in Australia, New Zealand and other countries.
Asphalt A dark brown or black substance found in a natural state or, more commonly, left as a residue after evaporating or otherwise processing crude oil or petroleum.
ASTM American Society for Testing and Materials – It is a standard generally used in many countries.
Awning A roof cantilevered and projecting from a building. It is also known as a Canopy.


Back coat An organic coating on the reverse side of a pre-painted strip or coil, not intended for external exposure. Epoxy / Polyester / PU shall be used as back coat paint.
Barge cap A flashing covering the edge of the roof cladding at the gable end of a roof.
Bare Galvalume Aluminuim-zinc alloy coated steel without paint coating on top and back side. But it is generally coated with thin layer of acrylic on both the sides.
Base metal The steel substrate generally cold rolled steel of commercial or structural grade.
Base metal thickness (BMT) The thickness of the base metal before any subsequent coating.
Bird Screen Wire mesh used to prevent birds from entering the building through ventilators and louvers.
BIS Bureau of Indian Standard – a national body which governs the IS standards, ISI mark certification, other testing & researches to cater the needs of Indian Industries.
Bitumen Refer “Asphalt”.
Black rust Formation of aluminium oxide over the aluminium sheet or aluminium zinc alloy coated steel sheet. The Colour of aluminum oxide is in black Colour.
Blistering Formation of pimples or blisters on the paint coated surface is due to the zinc oxide formed beneath the paint layer. Entrapped moisture or water particle reaching the zinc surface will react and form zinc oxide (white rust) leads to blistering.
BOQ / BOM Bill of Quantities / Bill of Materials – generally given along with the drawing.
Box gutter A square or rectangular internal gutter between two roof surfaces or at a parapet wall.
Bullnose A shaped piece of roof cladding, curved near to a quarter circle on its outer end, and used predominately as verandah roof sheeting.
Butterfly roof A structure having two inward sloping roofs, draining to a centre gutter.
Butyl Rubber-like material produced by copolymerizing isobutylene with a small amount of isoprene. Butyl may be manufactured in sheets, or blended with other elastomeric materials to make sealants and adhesives.


Camber The deviation from a straight line of a side edge of metal cladding, flashing or unformed coil. A slight convex curve of a surface, such as in a roof sheet.
Canopy A cantilevered roof without walls over a doorway. Canopy is also known as an Awning.
Capillary The action that causes movement of moisture by surface tension between two surfaces in close contact. It is known as Capillary action, Capillary attraction and wicking.
Capping Sheet metal covers the roof or wall intersections to provide weather tightness. It is also called as flashing.
Catchment The roof or roof and wall area above a gutter, valley or penetration that will collect rainwater.
Cathedral roof A roof having a pitch over 45°.
Cathodic protection Cathodic protection is a procedure used to protect an object from corrosion by making it a cathode. To make it as a cathode, you have to attach an anode to it. Both have to be in an electrolyte such as earth or water.
Column A primary member used in a vertical position on a building to transfer loads from main roof beams, trusses or rafters to the foundation.
Chalking It is the result of weathering on an organic paint film and the degradation of which produces a chalky surface layer.
Chord A straight line drawn across a circle with each end touching the circumference.
Cladding Roof sheeting fixed to the roof structure, or wall sheeting fixed to walls as the weather-resistant surface of a building.
Clip A plate or angle used to fasten two or more members together.
Cleat A metal strip, plate or metal angle piece, either continuous or individual (“clip”), used to secure two or more components together.
Coating mass The weight of the metallic protection given to steel by a zinc or aluminium / zinc coating, usually described in grams per square meter (g/m2). E.g. Z120, AZ150. Sheet or coil is measured and described as including both sides.
Coil Metal sheets in coil form are flat products wound into rolls and having a rectangular cross-section, the width of which is much larger than the thickness.
Coil coating The continuous application of a metallic or organic coating to a metal coil.
Cold forming The process of using press brakes or rolling mills to shape steel into desired cross sections at room temperature.
Cold rolled The process of passing the steel sheet between the forming rollers to get the desired cross section/profile at room temperature.
Condensation The process by which a vapour such as water vapour changes phase to a liquid.
Conduction The transmission of heat through a material by contact between the particles of matter.
Convection The transport of heat within a gas or a fluid by the relative movement of those parts that differ in density.
Corrosion The deterioration of a substance, usually a metal, or its properties, because of a reaction with its environment.
Corrugate A profiled sheet formed into a series of sinusoidal or circular curves.
Cover width The net width of sheeting less the lap. It is also known as Effective width.
Creep The metal deformation or a change in shape that increases continuously when under constant load or stress.
Crest The top most point of any profile sheet.
Crimp curving A method of forming a curve on profiled sheeting by discrete indentations.


Depth The vertical height of a rib or gutter.
Dew point The temperature at which water vapour condenses, which varies with the relative humidity and the pressure.
Downpipe A pipe used to carry roof water from gutters and roof catchments to drains or storage tanks.
Downspout Refer “Downpipe”.
Drip flashing A metal strip placed along the edge of a roof to divert water
Dry film thickness (DFT) The thickness of a cured organic coating applied to a metal substrate.
Ductility The ability of metal to withstand distortion without fracture.
Duplex coating A two-coat protection system applied to a metal product whereby a metallic coating is subsequently coated with an organic coating.
Durability The ability of a material to withstand the action of the elements and perform the structural and functional requirements of the design performance criteria for a specified time.


Eave Height The vertical dimension from finished floor to the eave.
Eaves The protruding edge of a roof slope. When enclosed is known as a soffit.
Eave gutter An external roof gutter attached to a roof overhang or the lower edge of a roof.
Elastic Limit The furthest point to which an elastic body can be stretched and still return to its original size and shape.
Electrolytic corrosion Galvanic corrosion commonly resulting from the contact of two dissimilar metals when an electrolyte, such as water, is present.
Emittance The property of a surface to reradiate infra-red heat. Polished or shiny metal surfaces are poor emitters and dull dark surfaces are good emitters.
End lap Over-lap of panels or sheets along its length and it is recommended to have such end-laps along the purlin line.
EPDM A thermosetting synthetic rubber of “ethylene propylene diene monomer” or “terpolymer “used as a resilient part of a sealing washer or as a roof membrane.
Erosion The attrition of organic or metal coatings by natural weathering.
Expansion joint A joint in a long length of roof cladding, gutter, spouting or flashing designed to allow for thermal expansion and contraction.


Fall The slope of roof or wall cladding or gutter usually expressed in degrees, or as a ratio of vertical height to horizontal distance (e.g. 1 in 20= 3°).
Fanning It is a kind of geometrical distortion when spreading of roof or wall cladding at the gutter or ridge that results in the sheeting being out of square with the building. It is also known as Sawtoothing.
Fascia A decorative trim or panel projecting from the face of a wall.
Fascia gutter A square gutter formed to resemble a fascia.
Fasteners Nails, screws, clips, and bolts, which are used to fix components of a roof assembly together.
Fatigue The condition that induces weakness or cracking in a metal component by continued fluctuating stress, resulting in fracture.
Ferrous metal Ferrous group of metals is composed mainly of iron. They may have small amounts of other metals or other elements added such as carbon, manganese, nickel, chromium, tungsten etc., to give the required properties. Most (but not all) ferrous alloys are slightly magnetic and give little resistance to corrosion e.g. all ferrous alloys will exhibit some degree of oxidation called rust which has a distinct reddish Colour.
Film thickness The thickness of paint or other coating usually expressed in micron meters (microns). Wet film thickness is the thickness of a coating as applied. Dry film thickness (DFT) is the thickness after curing.
Fixing It is the method of attachment of cladding to the frame achieved by the use of fasteners.
Flashing A sheet metal closure which functions primarily to provide weather tightness in a structure and secondarily to enhance appearance
Flat roof A roof having a slope between 0° and 5°.
Free roof A roof without enclosing walls e.g. a carport.
Fretting It is the damage on a metal surface or coating between adjacent surfaces, caused by movement and friction, e.g. during transportation.


Gable It is the generally triangular portion of a wall between the edges of a sloping roof. It is a wall plane above the eave level on the end wall resembling the shape of the truss.
Gable roof A gable roof has two upward sloping sides that meet in middle at the ridge. To be a true gable, both sides must slope at the same angle. Simply it is called as ‘A’ type roof.
Galvalume Aluminium-Zinc alloy or ZINCALUME alloy of 55% aluminium, 43.4% zinc and 1.6% of silicon.
Galvalume Steel Continuously hot dip coated Galvalume alloy over steel and described as AZ or AZM. PPGL and NCGL materials are typical Galvalume steels.
Galvanized steel Steel protected against corrosion by a hot-dipped zinc-coating and described as Z.
Galvanizing It is a process of coating zinc over steel sheet. PPGI sheets are galvanized by continuous hot dip Coating process where CR steel is continuously fed into the molten bath of zinc. Coating mass of zinc is specified as Z120, it denotes 120 grams of zinc is coated over 1 sq. meter area of base metal on both the sides.
Gambrel roof A roof that has two pitches on each side.
Gauge The thickness of metal described in mm or inches, previously known as a gauge non-measured number.
Girt A structural horizontal wall member in a wall between columns, used to fix or support wall sheeting.
Gloss value It is the amount of light reflected by the paint film at 60° and the values range between 0-100 GU (Gloss Unit). Gloss value more than 70 GU is termed as High-gloss.
Guard film A plastic film applied to surface of metal sheet or strip to give temporary protection to the finish.
Gutter A channel formed to collect and carry water away from a roof, variously described as internal, external, box, eaves, and valley.


Hem A flat but open metal edge folded 180°. It is also called a safety edge.
Hex head A self-drilling or self-tapping screw with a hexagon (six sided) head.
Hip It is the inclined external angle formed by the intersection of two sloping roof planes. It runs from the ridge to the eaves.
Hip Roof A roof which rises by inclined planes from all four sides of a building.
Humidity The amount of water vapour suspended in the air. It is the state or quality of being damp.
HVAC Heating, Ventilating and Air conditioning.


Impermeable A barrier preventing the passage of a liquid or vapour. Also known as a Vapour Barrier.
IS standard Indian Standard – followed in India and it is governed by Bureau of Indian Standards.
ISO International Organization for Standardization – It is an international body which defines product, process, material and other testing standards. It certifies QMS, EMS & OHSAS and other processes.


JIS   Japanese Industrial Standard – Used in countries like Japan, China, Korea, Taiwan etc.


Kilogram Force (kgf) The kilogram-force is a gravitational metric unit of force. It is equal to the magnitude of the force exerted by one kilogram of mass in a 9.80665 m/s2 gravitational field on earth. 1 kgf = 9.8066 N (Newton).
Kilo Newton (kN) A metric or SI unit of force, used to measure point or live loads. 1000N = 1 kN.
Kilo Pascal (kPa) A metric or SI unit of stress or pressure. 1 kPa = 1 kN/m2.


Lap That part of a flashing or sheet that overlaps or covers any portion of the same / dissimilar shaped component, and variously described as overlap and underlap.
Lap tape An adhesive strip made from UV resistant materials used as a joint sealant or part of a roof system.
Lean-to A mono-pitch or single slope roof attached to another structure but at a lesser pitch (roof slope).
Leeward The opposite direction to that from which the wind is blowing (windward).
Lip Extended / insufficient web which are free on side edges of the profiled sheet.
Load Force exerted on a structural member. Examples like dead load, live load, Impact, Seismic, Wind and Crane loads etc.
  Dead Load: Permanent load applied to a structure. Example weight of secondary structures, roof, floors of multi-storied building, walls, canopies etc which are permanent construction.
  Live Load: Temporary loads such as people on the roof, material stacked on the roof, snow, etc.
Louver An opening provided with slotted fins (fixed or moveable) to allow air flow.


Maintenance A planned set of activities regularly performed during the design working life of a structure, to enable it to fulfill durability and functional requirements. Maintenance can be divided into two types
  Normal: That which can be undertaken without special equipment e.g. cleaning, washing.
  Special: That which requires specialized skills or equipment.
Mansard roof A roof with two pitches, having a break in the slope, the lower part being steeper than the upper.
Masonry Anything constructed of materials such as bricks, concrete blocks, etc.
Mega Pascal (MPa) A metric or SI unit of stress or pressure, Used to measure yield and tensile strength of material. 1 MPa = 1 N/mm2
Metallic coating It is the continuous hot dip coating of zinc or aluminium-zinc alloy over the base metal on both the sides to improve the corrosion resistance.
Meter Unit of length in SI units. (1m=1000mm=3.28 feet)
Micron (or) A millionth of a meter, used as a measure of the thickness of metallic and organic films. It is also known as a Micron. (1µm=0.001mm=0.000001m)
Micron meter  
Mono-pitch roof A roof having one constant slope with no ridge, also known as mono-slope or lean-to.


Non-ferrous metal Metals made from elements other than iron.
Neutral-cure silicone A sealant used to join metal that has a neutral pH and does not corrode metal.


Oil canning The degree of waviness on flat surface of cold rolled steel products like coil and roof/wall panels. Residual stresses during coil manufacturing can cause oil canning.
  Full center: The coil is longer in the middle of the strip shall lead to ripples and buckles near the mid-coil area.
  Wave edge: The coil is longer along the edge of the strip shall lead to oil canning.
  Panel fabrication: Slitting (releases residual stresses) and roll forming of profiles (pushing the uneven metal to the edges as ribs are formed from the mid of the coil to outward edge).
Organic coating The paint film of a pre-painted metal product or a laminate film of a laminated metal product.
Oxide A chemical compound of oxygen and metal that will form as a film on the surface of metals on exposure to the atmosphere.


Panel The exterior roof and wall sheeting for a metal building system.
Parapet wall The portion of the vertical wall which extends above the roof line.
Peak box The finish trims at the highest point of the rake.
Perforation Deterioration of metal due to corrosion or erosion that results in a hole
Permeability The measure of the rate of a porous material to permit a gas or liquid to move through it in a unit time, area, and pressure. It is dependent on the density of both materials and the temperature.
pH value A unit-less logarithmic measure of acidity or alkalinity graduated from 0-14. pH 7 is neutral, below which is more acidic, above which is more alkaline.
Pitch The distance between the centers of consecutive crest / rib / crimping is termed as pitch.
  The slope or rake of a roof expressed in degrees from the horizontal or as a ratio of vertical height to horizontal distance. It is also known as fall or roof slope.
  Example 1 in 20 = 3°, 1:12 means 5°
Polycarbonate A clear thermoplastic polymeric resin formed into matching roof and wall cladding profiles or curved flat sheeting used to provide natural roof lighting.
PPGI Pre-painted Galvanized steel.
PPGL Pre-painted Galvalume steel.
Pre-painted Base metal strip or sheet, in line painted to give protection or aesthetic appeal prior to subsequent forming, shaping or fabrication. It is also known as pre-coated strips or coils.
Primer Prepares the metallic coated surface for better adhesion of paint. Polyurethane (PU) or epoxy shall be used as primer.
Profile The cross-section of metal cladding, generically known as corrugated (sinusoidal), ribbed (trapezoidal), troughed, boxed or tray.
Pucker The unacceptable distortion of metal flashings due to an incorrect fit.
Pullout The failure of a fastener when it is pulled out of the structure, e.g. by the uplift force of the wind.
Pullover The failure of the sheeting when it pulls over the head of the fastener or washer, e.g. by the uplift force of the wind.
Purlin A horizontal secondary structural member bolted to the trusses which transfers the roof loads from the roof panels to the trusses or rafters, usually a Z or C shape.
PVC A clear or opaque polyvinyl chloride thermoplastic resin, formed into matching cladding profiles to provide natural roof and wall lighting.
PVDF Polyvinylidene fluoride – Top coat paint, it has got high gloss value and good Colour retention property (UV resistance).




Radiation The transmission and emission of infra-red energy in the form of electro-magnetic waves.
Rafter A sloped structural member that extends from the ridge to eave designed to support secondary members and the roof cladding.
Rake The intersection of plane of the roof and the plane of the end wall. Rake is the edge of the roof that runs from the eave to the ridge.
RAL code International Colour matching system. It is always advisable to refer the Colour shade by RAL code to avoid the ambiguity in referring the name of the Colour shade as per our perception.
Red rust The formation of a reddish-brown oxide on the surface of steel or iron.
Relative humidity The ratio of the mass of water vapour in a volume of air, compared to the value that saturated air could contain at the same temperature and pressure.
Rib A longitudinal up-stand produced by roll-forming, folding or crimping to strengthen or stiffen metal cladding.
Ridge line Highest point on the roof of a building which creates a horizontal line running along the length of the building.
Ridge Cap Continuous metal strip (normally conforming to roof panel configuration) used to close roof material along the ridge line.
Ridge vent A ridge vent runs the entire length of the roof peak which allows the air circulation.
Rivet A small headed hollow tubular fastener with an expandable body for joining sheet metal capable of being fastened from one side. It is also known as a Blind or Pop Rivet.
  A small headed solid fastener suitable for penning requiring access to both sides. It is also known as a Tinmans rivet.
RMP Regular Modified Polyester. It is a polyester based paint generally used as top coat paint of PPGI and PPGL steel coils.
Roll formed A manufacturing process by which metal is progressively formed from flat sheet or coil into a profiled sheet by a series of shaped rolls.
Roof The surface of a structure or building designed to shelter the space below it against the elements, and to discharge rainwater outside the building.
Roof overhang A roof extension beyond the end wall or sidewall of a building.
Roof slope or pitch The inclination of a roof. It is usually stated in terms of vertical rise as compared to horizontal coverage, as 1: 12 refers to 1 foot rise for every 12 feet horizontally.
  It is expressed as ratio of rise to run.
  Rise – Vertical dimension of a slope. Run – Horizontal dimension of a slope.
Roofing The act of constructing or covering a roof.
Roofer A person who covers a roof.
Roof Extension See “Roof Overhang”.
Running meter See “Meter”.


Safety mesh A safety wire netting used to prevent workers falling through a roof. It can also function as an underlay support.
Saw tooth roof A trussed roof construction that is in the shape of the teeth of a saw, requiring gutters at the bottom of the near vertical face.
Screw gun An electric or battery driven drill, with a torque limiting or depth limiting device, used for driving self drilling, self tapping screws or other types of screw.
Sealant Any material which is used to close up cracks or joints to prevent leaks.
Section properties Values assigned to specific profiles determined by their geometrical shape.
Self Drilling screw A fastener which drills and taps its own hole. Commonly used to attach panels to purlins and girts. It is also called as SDST or SDS screws.
Selling unit It is the UOM which defines the material quantity for billing.
Shear The scissor action of any tool used to cut metal.
Sheet Flat metal over 0.15 mm and less than 3 mm in thickness, of exact length and over 450mm in width.
Sheeting A metal or any material used to form sheet/panel to cover the structure.
Shoe A downpipe angled at the discharge point. It is also called as downpipe shoe.
Side-lap A term used to describe the lap condition occurring at the side or along the width of panels or sheeting.
Sill flashing A flashing at the bottom of a window or door opening or penetration. Also known as a Tray Flashing.
Skew A roof at an angle or out of square.
Skylight A unit of plastic sheet, glass or an Acrylic dome providing natural light through a roof.
SMP Silicon Modified Polyester – Top coat paint with good heat resistance property.
Snips A metal tool used to cut metal, having variously shaped cutting blades, variously described as straight, curved, gilbow, circular, aviation, left-hand, right-hand, or tinmans.
Soffit The underside covering of any portion of a metal building usually at a roof overhang.
Span The distance between the supports of beams, girders or trusses.
Square meter It is the unit of an area in SI units. (1m2=10.76 sq ft)
Stitch Screw A self-tapping screw used to connect panels together at the side lap.
Substrate The metallic surface to which a metal, organic or laminated film finish is applied.
Swarf Fine metallic filings or chips produced as debris from drilling, cutting, or grinding metal on a roof.


Tape Sealant Sealant furnished in a continuous roll, normally used for sealing roof panel end laps and side laps.
Temper A hardness condition of metals determined by a manufacturing process or subsequent annealing and described as soft, 1/4 hard, 1/2 hard, or full hard.
Tensile strength The tensile limit when metal breaks under load, measured by the load divided by the original cross section and expressed in MPa. (Mega Pascal). It is also known as Ultimate tensile strength (U.T.S.).
Thermal conductivity The rate at which heat passes through a material expressed as the amount of heat that flows per unit time, area and distance.
Tile An interlocking metal pressing, shaped to resemble a clay tile.
Total coated thickness (TCT) The measure of the total of the base metal thickness, plus any additional metal or organic coating.
Tolerance A fractional allowance for variations from the specified standard parameters like weight, dimensions, etc., in construction
Translucent panel See "Skylight".
Trapezoidal Profiled roof or wall cladding with longitudinal ribs angled similarly to a trapezoid.
Truss A structure, acting like a beam, made up of three or more members with each member designed to carry a tension or compression force.
Turnbuckle A form of threaded coupling connecting two metal rods lengthwise that regulates the distance between them by a turning motion,


UOM Unit of measurement. 


Valley It is the internal angle formed by the intersection of two sloping roof planes to provide water runoff.
  In any profiled sheet, channels formed between the crests/ribs to provide water runoff.
Valley Gutter A channel formed to carry water from a common low point in the roof. This condition is usually created when two buildings are joined side by side.
Ventilation It is a process of supplying fresh air to an enclosed space and removing from it air contaminated by odors, gases, or smoke.


Walkway A permanent or temporary structure placed over metal roof cladding to enable access without causing damage or imposing a point load on the cladding.
Wall Vertical structure which provides the side structure for a building or defines an area.
Weathering Deterioration, such as the oxidation of metals, or chalking of pre-coated materials due to atmospheric exposure.
Web Side wall of valley or rib of a profile sheet.
Wet storage stain Corrosion effects due to condensation or rain penetration of nesting profiles. It is also known as White Rust for galvanized, Black Rust for Aluminium Zinc coating, and Black Stain for Aluminium.
White rust The visible white corrosion product found on galvanized coatings in protected, unwashed, cut edges or micro-cracked areas.
Wicking It is the movement of water through a porous material by capillary action.
Work hardening The reduction of metal ductility caused by cold working or movement in service.




Yield point The first stress point at which some metals will plastically and permanently deform.
Yield strength Indication of maximum stress that can be developed in a material without causing plastic deformation. It is the stress at which a material exhibits a specified permanent deformation and is a practical approximation of elastic limit.


Z or Zed purlin It is the cross section of purlin/girt in the shape of ‘Z’ with or without pre-punched holes for fixing.
Zinc aluminium coating It is continuous hot dip coating process with an alloy of 5% aluminum and 95% zinc over the CR steel. It is also known as Galfon steel.