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Although the information contained in this Code has been obtained from sources believed to be reliable, New Zealand Metal Roofing Manufacturers Inc. makes no warranties or representations of any kind (express or implied) regarding the accuracy, adequacy, currency or completeness of the information, or that it is suitable for the intended use.

Compliance with this Code does not guarantee immunity from breach of any statutory requirements, the New Zealand Building Code or relevant Standards. The final responsibility for the correct design and specification rests with the designer and for its satisfactory execution with the contractor.

While most data have been compiled from case histories, trade experience and testing, small changes in the environment can produce marked differences in performance. The decision to use a particular material, and in what manner, is made at your own risk. The use of a particular material and method may, therefore, need to be modified to its intended end use and environment.

New Zealand Metal Roofing Manufacturers Inc., its directors, officers or employees shall not be responsible for any direct, indirect or special loss or damage arising from, as a consequence of, use of or reliance upon any information contained in this Code.

New Zealand Metal Roofing Manufacturers Inc. expressly disclaims any liability which is based on or arises out of the information or any errors, omissions or misstatements.

If reprinted, reproduced or used in any form, the New Zealand Metal Roofing Manufacturers Inc. (NZMRM) should be acknowledged as the source of information.

You should always refer to the current online Code of Practicefor the most recent updates on information contained in this Code.


This Code of Practice provides requirements, information and guidelines, to the Building Consent Authorities, the Building Certifier, Specifier, Designer, Licensed Building Practitioner, Trade Trainee, Installer and the end user on the design, installation, performance, and transportation of all metal roof and wall cladding used in New Zealand.

The calculations and the details contained in this Code of Practice provide a means of complying with the performance provisions of the NZBC and the requirements of the Health and Safety at Work Act 2015.

The scope of this document includes all buildings covered by NZS 3604, AS/NZS 1170 and those designed and built under specific engineering design.

It has been written and compiled from proven performance and cites a standard of acceptable practice agreed between manufacturers and roofing contractors.

The drawings and requirements contained in this Code illustrate acceptable trade practice, but recommended or better trade practice is also quoted as being a preferred alternative.

Because the environment and wind categories vary throughout New Zealand, acceptable trade practice must be altered accordingly; in severe environments and high wind design load categories, the requirements of the NZBC will only be met by using specific detailing as described in this Code.

The purpose of this Code of Practice is to present both Acceptable Trade Practice and Recommended Trade Practice, in a user-friendly format to ensure that the roof and wall cladding, flashings, drainage accessories, and fastenings will:

  • comply with the requirements of B1, B2, E1 E2 and E3 of the NZBC;
  • comply with the design loading requirements of AS/NZS 1170 and NZS 3604 and with AS/NZS 1562;
  • have and optimised lifespan; and
  • be weathertight.

COP v24.03:Glossary; Definitions

2.1 Definitions 

The glossary provides a list of definitions for commonly used terms in the roof and wall cladding industry.

2.1A Definitions

Absorption The ability of a material to accept liquid within its body. 
Acceptable solution A prescriptive means of compliance with the performance requirements of the NZBC, approved by the Ministry of Business, Innovation and Employment. 
Acceptable trade practice The minimum standard of design and workmanship to comply with the performance requirements of the NZBC. 
Accessories Gutters, ridge capping, ventilators, flashings, downpipes, brackets and their fixings. 
Action-effect A force due to a load. 
Acute angle An angle that is less than 90° 
Alloy A metallic substance composed of two or more chemical elements, at least one of which is a metal, combined to give enhanced strength, resistance to corrosion or lower the melting point. 
Aluminium/zinc A continuously hot-dipped coating used to protect steel against corrosion, commonly consisting of 45% zinc and 55% aluminium by mass, generally conforming to AS/NZS 1397.AZ; Zincalume®; Galvalume; Aluzinc; Duralume
Anneal Softening a metal by heating, to restore or increase its ductility. 
Annular grooved nail A nail having a shank deformed with a series of circular grooves. 
Anodic Galvanic corrosion can occur when two metals are connected in moist or wet conditions. The anodic metal, being more active (-), sacrifices itself to protect the more noble metal in the galvanic series, cathodic (+). 
Applied finish A surface finish applied to metal tiles, shakes, or accessories subsequent to pressing or forming. Post-form painting
Approved Any documentation, solution or method that is accepted by a recognised authority. 
Apron A near-horizontal flashing with a vertical upstand that covers the intersection between a vertical and a horizontal or sloping surface. It can run across the roof profile (transverse) or in the same direction (longitudinal) and prevents water ingress or sheds water from a higher wall or roof onto a lower roof.Abutment flashing
Astragal A metal strap used to fasten downpipes to a wall.Standoff bracket
Asymmetrical profile A profile that has a different configuration on opposite sides of the horizontal centre axis. The opposite of symmetrical. 
Average Recurrence IntervalARI

The rainfall intensity in New Zealand is determined by the rainfall during a ten minute period, measured in millimetres per hour.

The ARI represents the expected timespan between exceedances of a given rainfall intensity.

Awning A roof projecting from a building, usually open on three sides.Canopy
Baby Iron A miniature corrugated profile rolled with 6 mm high ribs.Sparrow iron; mini-corrugate; and mini-iron
Backer coat An organic coating on the reverse side of a pre-painted strip or coil, not intended for external exposure. 
Back-out The condition when a fastener works loose due to timber shrinkage, thermal movement, vibration or an incorrect thread type. 
Barge flashing A flashing covering the intersection of a roof surface and a lower vertical surface or covering the intersection of a roof surface and a lower vertical surface.Barge roll; cover roll; ridge roll; barge mould; square barge
Base metal thicknessB.M.T.The thickness of the bare or base metal before any subsequent coating.Gauge
Battens A narrow timber, steel or polystyrene member attached to a roof or wall structure, used to attach metal cladding, metal tiles, shakes or shingles to the structure. It can also function as a spacer. 
Bay A wide pan of fully supported roof cladding laid between standing seams or rolls. 
Bead (a) A curled stiffening to a metal edge
(b) A rounded strip of sealant.
(c) A ball-shaped piece of solder or brazing.
Bend radius The formed outside radius on a flashing or sheeting. 
Blind Rivet A small-headed hollow tubular fastener with an expandable body for joining sheet metal; capable of being fastened from one side.Rivet.
Boot flashing A proprietary EPDM prefabricated flashing used to weatherproof circular pipes protruding from a roof or wall. 
Bossing The working of a malleable metal into a required shape, using wooden or plastic tools.Dressing
Box gutter (a)   A square or rectangular internal gutter between two roof surfaces or at a parapet wall.
(b) A square profile spouting attached to an external wall or fascia.
Brazing The joining of metals using an alloy with a lower melting temperature than either of the metals to be joined. 
Brittle roofing Flat, troughed or corrugated plastic, asbestos, or other sheeting that is or can become brittle. 
Broken bond Tiles laid so that the side laps of any two adjacent rows of tiles down a roof do not line up and are staggered or offset. 
Buckling A loss of the original shape of metal, by compressive bending, bearing or shear loading.kink; ding; wrinkle; bulge
Building Consent AuthorityBCAA Building Consent Authority accredited by the Ministry of Business, Innovation and Employment (MBIE) to issue building consents.
BCAs are usually local and district councils, but they can also be regional councils (for dams) and private organisations.
Building Insulation BlanketBIB

Lightweight, flexible bulk insulation that is supplied in a continuous roll.

 F.F.B.I.B.Building insulation blanket faced with foil. 
Building paper An absorbent permeable membrane made from treated kraft paper, placed under roof or wall cladding.permeable roofing underlay
Bullnose A shaped piece of roof cladding, curved near to a quarter circle on its outer end, and used predominately as veranda roof sheeting. 
Butt strap A soaker under flashing, used as an expansion joint. 
Butterfly roof A structure having two inward sloping roofs, draining to an internal gutter. 
Camber (a) The deviation from a straight line of a side edge of metal cladding, flashing or unformed coil.
(b) A slight convex curve of a surface, such as in a roof deck.
(c) A load-induced curve, or a pre-induced curve to counter the effect of a member bending under load.
Canopy A cantilevered roof without walls over a doorway.awning
Canterbury prickle A small shaped capping to a roof rib at a change of pitch.rib cap
Capillary The action that causes movement of moisture between two surfaces in close contact.capillary action; capillary attraction; wicking.
Capillary groove An indentation formed in the edge of a metal cladding profile or flashing to prevent capillary action.capillary barrier; anti-capillary edge 
Capping The top flashing of a wall, parapet or balustrade.coping
Cat ladder A ladder fixed vertically to a wall or used on a steeply pitched roof as a temporary means of access.roof ladder
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 The protection of one metal by another by the more active (Anodic) metal reacting with the elements in preference to the othersacrificial protection
Cavity construction A roof or wall construction that provides a drained air gap separation from the external cladding. 
Chalking The result of weathering on an organic paint film, the degradation of which produces a chalky surface layer. 
Chase A groove or recess cut into a concrete or block wall to accommodate a flashing. 
Chord (a) The horizontal member (bottom chord) or a pitched member (top chord) of a truss.
(b) 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. 
Cleat A continuous concealed clip without external fixings used to fasten roof cladding or flashings. 
Clerestory roof A roof covering of a high vertical window between two opposing roof planes of different heights, used for borrowed light or ventilation. 
Clip A small fixing used to secure roof cladding, flashings or pipes to the structure. 
Closure strip A metal or plastic flashing, blocking open ribs or pans, to prevent the ingress of water, wind, and vermin.bird-proofing; filler block; foam seal
Coating mass The weight of the metallic protection given to steel by a zinc or aluminium/zinc coating, usually described in grams per square metre (g/m2), e.g., Z 450, AZ 150. Sheet or coil is measured and described as including both sides. Articles which are hot-dipped after fabrication are measured and described as including one side only. 
Code of practiceCOPPrescriptive quantitative and qualitative criteria by which a product or system can comply with specified performance requirements. 
Codemark Codemark is a product certification scheme, supplied by an accredited certification body, showing that a product meets the requirements of the Building Code. Building Consent Authorities must accept a Codemark product-certificate as evidence of compliance with the NZBC.  
Coil-coating The continuous application of a metallic or organic coating to a metal coil. 
Cold rolling A metal thickness reduction manufacturing process, by applying pressure to metal coil at moderate temperatures. 
Cold Soldering Using a sealant or adhesive to bond two pieces of metal together.Soldering
Collar A round over-flashing attached and sealed to a pipe to weatherproof a penetration. 
ColorCote® Pre-painted steel and aluminium for use as roofing, wall cladding, or roofing accessories, manufactured by Pacific Coilcoaters.

Pre-painted steel for use as roofing, wall cladding, or roofing accessories, manufactured by New Zealand Steel

Composite roof A factory insulated panel with metal cladding on both sides used to cover a roof or a wall.sandwich panel; composite panel; panel roof; cool room panel
Concealed fastening A method of fixing a roof by means of hidden, or secret fixing clips or brackets.secret fix; clip fix
Condensation The process by which a vapour such as water vapour changes phase to a liquid.Sweating
Conduction The transmission of heat through a material by contact between the particles of matter. 
Contractor A person or company who enters a verbal or written agreement with another party to perform an agreed scope of work.roof fixer
Convection The transport of heat within a gas or fluid by the relative movement of those parts that differ in density. 
Corrosion The process by which something erodes because of a chemical reaction.rust
Corrugate A profiled sheet formed into a series of sinusoidal or circular curves.corrugated iron
Counter-batten A spacer of timber or steel fixed to a purlin or batten, running transversely to the purlin. 
Cover (a) The net width of sheeting less the lap.
(b) The net width of a flashing that covers sheeting.
effective cover
Creep (a) The metal deformation, or a change in shape that increases continuously when under constant load or stress.
(b) The change in a sheet's laying module when subsequent sheets are laid out of line or out of square.
Crest The top surface of a rib or corrugationcrown; rib
Crevice corrosion The rapid pitting corrosion that occurs in crevices, pockets, or fissures when a patina or oxide film is prevented from forming or reforming by the concentration or depletion of dissolved salts or oxygen in stagnant water. 
Cricket A metal roof flashing designed and constructed to divert water around a penetration and to avoid ponding.raised curb
Crimp curving A method of forming a curve on profiled sheeting by discrete indentations; causing a concave curve in the rib or a convex curve in pan 
Crown The top of a curved roof or rib. 
Cupola A small roofed structure on a ridge to provide ventilation, or designed for aesthetic purposes. 
Curb A gutter or apron flashing around a penetration.kerb
Cyclonic winds Strong winds rapidly spiralling clockwise into a centre of low pressure in the Southern hemisphere.hurricane; typhoon
Deck The substrate of a structure that supports claddings that require to be fully supported. 
Decking A predominantly flat secret fixed roofing profile; includes trough and tray profiles.tray; secret-fixed trough
Deflection The deviation from a straight line induced by a load or action. 
Deformed shank nail Nails with annular, spiral or otherwise deformed shanks.enhanced shank nails
De-indexing The releasing of interlocking profiled sheets. 
Depth The vertical height of a rib or gutter.  
Design wind load The site design wind pressure in kilopascals (kPa) on a specific part of a structure, modified by pressure coefficients. 
Design wind speedVdesThe design wind load expressed as wind speed. 
Dewpoint The temperature at which water vapour condenses, which varies with the relative humidity and the pressure. 
Ding Permanent creasing of a rib or sheet, usually due to damage on a roof, resulting in structural depreciation. 
Diverter (a) A penetration flashing design used to prevent the accumulation of dirt and debris, which diverts the water runoff by folding the back curb at an angle to the penetration.
(b) An angle fastened to a flashing to channel water away from a penetration, obstruction or a wall.
Dog-ear A three-dimensional box-like internal corner formed in metal without cutting.pig's lug; stop end
Dominant opening An opening in the external surface of a closed building, greater than opposing openings, which directly influences the internal wind pressure. 
Dormer A roofed window structure projecting at right angles from a sloping roof surface. It can be configured as a shed dormer, gable dormer, or eyebrow dormer. 
Downpipe A pipe used to carry roof water from gutters and roof catchments to drains or storage tanks.downspout
Downturn That part of the trough of a sheet turned down into a gutter.turndown
Drape curving The use of metal cladding to cover a curved roof, using its own weight and not being pre-curved.spring curving
Dressing The operation of flattening or beating metal into the required shape.bossing
Drip (a) An outward projecting edge formed on a metal flashing to direct water away from the building or to avoid capillary action.
(b) A step or break in a roof or gutter, across the direction of fall.
birds beak; tip; kick; break
Dropper A spouting or gutter outlet.pop
Dry film thicknessDFTThe thickness of a cured organic coating applied to a metal build
Ductility The ability of metal to withstand elongation without fracture. 
Duopitch A roof having two differing sloping pitches. 
Durability The ability of a material to withstand the corrosive action of the elements, and comply with the structural and functional requirements of the design performance criteria for a specified time. 
Dutch gable A type of roof frame that is partially hipped but which terminates as a gable. 
Dynamic pressure Fluctuating load normally caused by wind forces. 
E2/AS1 An Acceptable Solution to the NZBC clause E2 External Moisture issued by the MBIE. 
Eaves The protruding edge of a roof slope. When enclosed it is known as a soffit. 
Eaves gutter An external roof gutter located under a roof overhang or the lower edge of a roof.spouting
Edge protection A guardrail or restraint designed to prevent a person from reaching over a roof edge or falling from a height. 
Elastic limit The limit to which a material can withstand stress under load without any noticeable or measurable permanent deformation. 
Electrochemical series The order in which metals react with one another in an electrolyte, with the electro-negative metal corroding in preference to the electropositive metal.electromotive or galvanic series
Electrolysis The chemical change or decomposition produced in an electrolyte by an electric current. 
Electrolyte A solution such as water that contains ions, thereby becoming electrically conductive. 
Electrolytic cell A cell containing an electrolyte which produces an electrochemical reaction when an electric current passes through it. 
Electrolytic corrosion Galvanic corrosion commonly resulting from the contact of two dissimilar metals when an electrolyte, such as water, is present. 
Elevation The part of a drawing which shows the front, side or end view of a structure. 
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. 
EPDMEPDMA 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. 
Escarpment A steeply sloping face separating two relatively level plains, where the plains’ average slope is less than 5°. 
Eutectic point The melting point of an alloy that is lower than the melting points of the elements or metals within it. 
Expansion joint A joint in a long length of roof cladding, gutter, spouting or flashing designed to allow for thermal expansion and contraction. 
Eyebrow dormer A roofed window structure with a curved roof projecting from a sloping roof surface. 
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 The spreading of roof or wall cladding at the gutter or ridge that results in the sheeting being out of square with the building.sawtoothing; creep
Fascia board A vertical board fixed to the bottom of the rafters, or trusses, to carry a spouting or gutter. 
Fascia gutter (a) A square gutter formed to resemble a fascia.
(b) A concealed eaves gutter system that interlocks with a vertical or near-vertical metal facing.
Fasteners Nails, screws, clips, and bolts, which are used to fix components of a roof assembly together.fixings
Fatigue The condition that induces weakness or cracking in a metal component by continued fluctuating stress, resulting in fracturing. 
Filler blocks Shaped closed-cell plastic pieces inserted into the rib ends or pans of metal cladding, to prevent the ingress of wind, water and vermin.seal; profiled foam; foam sealer
Fillet A supporting infill, installed at the point where vertical and horizontal surfaces meet, to support flashings and to avoid the build-up of dirt and debris in a sharp corner. 
Film thickness The thickness of paint or other coatings usually expressed in microns. (µm). Wet film thickness is the thickness of a coating as applied. Dry film thickness is the thickness after build
Finial A decorative element added to the end of a ridge, or the top of a spire or dome, to emphasise the feature. 
Fixing The method of attachment of cladding to the frame using fasteners. 
Flame retardant A material to which a substance has been added to reduce or retard its tendency to burn. 
Flashing (a) A metal covering, built in to prevent moisture movement or the ingress of water to the inner parts of a building.
(b) A component used to weatherproof, vermin-proof or seal the roof and wall cladding corner, ridge, perimeter, penetration, expansion joint, valley, gutter and other places where the roof covering is interrupted or terminated.
Apron; Barge; Back; Capping; Corner; Curb; Overcloak; Raking; Ridge; Secret; Sill; Skirt; Soaker; Soft-edge; Stepped.
Flat roof A roof having a slope between 0° and 5°. 
Flux A chemical liquid or substance used to clean and remove oxide or other films from metal prior to soft or hard soldering or brazing. 
Folding A manufacturing method used to permanently deform metal over a small radius to the desired angle.brake pressing
Freeboard The height of the watertight portion of a gutter or profile above the design water level at maximum rain intensity.  This is to allow for wave action or impediments in the sole of the channel that may otherwise cause overflowing. 
Free roof A roof without enclosing walls; e.g., a carport. 
Fretting Surface damage to metal or the coating between adjacent surfaces caused by movement and friction; e.g., during transportation. Normally, fretting only causes aesthetic damage. 
Fully supported cladding Metal cladding that requires a solid substrate to provide strength for wind or point loads.tray roofing; standing seam sarked roof
Gable The triangular end wall surface of a building above the plate line where the rafters meet the apex at the ridge. 
Gable roof A ridged roof having two slopes only, with a gable at each end. 
Galvanised steel Steel protected against corrosion by a hot-dipped zinc-coating described as Z. 
Galvanising The process by which steel is coated by dipping it into a bath of molten zinc, measured by weight in g/m2 or thickness in microns (μm) 
Gambrel A roof that has two pitches on each side, similar to a Mansard roof. 
Gauge The thickness of metal described in millimetres or inches, previously known as a non-measured number. 
Geothermal hotspot A location that exhibits any geothermal activity such as steam, water or fumes emitting from the ground, hot water or mud pool. 
Girt A structural horizontal wall member in a wall between columns used to fix or support wall sheeting. 
Good trade practice Trade habits used by members of an industry, having a history of successful usage and having a higher standard than Acceptable Trade Practice. 
Grade The mechanical strength of a metal complying with relevant standards. 
Groover A hand tool used for seaming sheet metal. Also known as a Seamer. 
GRPGRPGlass fibre reinforced polyester translucent or opaque sheeting, used for roof lighting and manufactured to match profiled sheeting. 
Gutter A channel formed to collect and carry water away from a roof, variously described as internal, external, box, eaves, valley, secret, hidden, and raking. Spouting refers specifically to an external gutter. 
Half-round A spouting or eaves gutter having a half-circle cross-section. 
Hard Soldering Using an alloy of silver and copper to bond two pieces of compatible metals together at approximately 735°, also known as silver soldering or brazing.soldering; silver soldering; brazing
Head flashing Flashing at the top of an opening or penetration. 
Hem A flat but open metal edge folded 180°.safety edge
HertzHzA metric or SI unit of frequency equal to one cycle per second used when cyclic testing metal roof and wall cladding. 
Hex head A self-drilling or self-tapping screw with a hexagon (six-sided) head. 
Hidden Gutter An internal gutter that runs parallel to the roof pitch. Hidden gutters are commonly found beside penetrations positioned close to the eaves. 
High strength Unannealed metals that have a high yield strength relative to their ultimate strength. 
Hip The external angle formed on a roof where two inclined faces meet. 
Hipped roof A roof with a level eave and with its ends inclined as well as its sides. 
Holiday A small pinhole or area where a liquid, applied paint coating or laminate film material is missing.skip
Hook An open hem used on a hidden under-flashing to prevent water ingress. 
Humidity The amount of water vapour suspended in the air. The state or quality of being damp. 
Impermeable A barrier preventing the passage of a liquid or vapour.vapour barrier
Inert catchment corrosion The phenomenon where rainwater or condensation, flowing over inert materials such as glass, plastic, or coated metals cause accelerated corrosion of downstream galvanised metal. 
Internal Gutter A gutter inside the building envelope. In the COP terminology, this applies specifically to those that run transverse to the roof pitch.Hidden gutter, Secret gutter
Interstitial condensation Condensation that occurs within an enclosed cavity of a wall or roof. 
Jenny A hand tool used to turn an edge on a curved flashing. 
Joggle A double offset fold used to accommodate metal thickness.crank
Kilonewton (kN) A unit of force applied to a specific area equalling a thousand Newtons. As the unit value of a Newton is inconveniently small, such forces are commonly expressed in kilonewton.Newton
KilopascalkPaKilopascal kPa A unit of pressure over an area equalling a thousand Pascals. As the unit value of a Pascal is inconveniently small, pressures are commonly expressed in kilopascals. 1 kPa = 1 kN/m2Pascal
Lap (a) That part of a flashing or sheet that overlaps or covers any portion of the same shaped component, and variously described as overlap and underlap.
(b) The total part of a flashing that laps another dissimilar component, including the cover.
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.shed roof
Leeward The opposite direction to that from which the wind is blowing (windward). The side sheltered from the wind. 
Licensed Building PractionerLBPA person issued with a renewable licence having satisfied the Building Practitioners Board that he or she meets the minimum standard of competence for each class of licence. 
Lightweight roof A roof cladding which has a mass not exceeding 20 kg/m2. 
Limit state A design method having two parts:
(a) Serviceability Limit State: The state when a building, or any part of it, becomes unfit for its intended use due to deformation or deflection.
(b) Ultimate Limit State: The state associated with collapse or failure, or when a building or any part of it becomes unstable or unsafe.
Load The value of a force resulting from an action. 
Load spreading washer A washer designed to give greater surface area to resist uplift pressures around the fastener head. In general, load-spreading washers should have a minimum thickness of 0.95 mm for steel and 1.2 mm for non-ferrous metal.profiled washer; cyclone washer; top washer
Loads Loads or actions that the structure or roof or wall cladding must be designed to support, as required by building standards or codes.
(a) A dead load is the weight of the permanent structure including the roof.
(b) A live load is a superimposed load such as foot traffic on the roof.
(c) A wind load is that load imposed on the structure by the action of the wind.
Local pressure coefficientklA factor applied to the design wind load due to the dynamic increase of the wind around the periphery of walls or roofs.kl; local pressure factor
Long-run Long length roll-formed roof and wall cladding fixed in one length without transverse laps. 
Low pitched roof A roof having a slope between 5° and 10°. 
Macro-climate The climate of a large geographical area. 
Maintenance A planned set of activities regularly performed during the design working life of a structure to enable it to fulfil durability and functional requirements. Maintenance can be divided into two types:
(a) Normal: That which can be undertaken without special equipment, e.g., washing.
(b) Special: That which requires specialised skills or equipment.
Mansard A roof with two pitches, having a break in the slope, the lower part being steeper than the upper.gambrel 
Membrane A non-metallic material used in conjunction with metal roof and wall cladding as gutters and penetrations, or as a fully supported roof cladding. 
Metal cladding Formed metal commonly used in the roofing industry in New Zealand; including metallic coated steel, aluminium, stainless steel, copper, and zinc. 
Micro-climate The climate of a small specified area; e.g., under eaves, near the seashore or in an enclosed cavity. 
Micro-cracking The small cracking that occurs on external or tension bends of galvanised and aluminium/zinc coating on steel during forming, the extent of which is interdependent on coating thickness and bend radius. 
MicrometreµmA millionth of a metre, used as a measure of the thickness of metallic and organic films.micron
Ministry of Business, Innovation and EmploymentMBIEThe Government department regulating economic development, science and innovation, labour, and building and housing. MBIE also authorises BCA’s and publishes the NZBC. 
Monel® alloys Any of a group of nickel-based alloys, developed in 1905, containing between 29% and 33% copper, with small amounts of iron, manganese, carbon, and silicon. Monel alloys are stronger than pure nickel and resistant to corrosion by many agents, including rapidly flowing seawater.
They can be fabricated readily by hot- and cold-working, machining, and welding. It is often used as rivets, fasteners or clips. Monel is a registered trademark of the International Nickel Company.
Monopitch A roof having one constant slope with no ridge.mono-slope; lean-to
Nesting profiles Cladding profiles that closely stack together. 
Netting An open weave lightweight material used under roof cladding as support for underlaymesh; wire netting
NewtonNThe force needed to accelerate one kilogram of mass at the rate of one metre per second squared in direction of the applied force. 
Neutral-cure silicone A sealant with a neutral pH, that does not cause corrosion. 
Night sky radiation A phenomenon where a roof can become up to 5°C colder than the ambient temperature by radiating heat to a clear night sky. 
Noble metal A metal that is less active or likely to corrode when in contact with others. 
Non-ferrous Metals made from elements other than iron. 
Notching tool A hand tool used to remove a section of flashing that fits over a rib. 
Obtuse angle An angle between 90° and 180°. 
OgeeOGA kind of sigmoid curve, somewhat shaped like an "S", consisting of two arcs that curve in opposite senses, so that the ends are parallel; it is often used in moulding. 
Oil canning Distortion in the form of waviness or centre fullness in a profiled sheet.canning; panning
Opalescent Having shimmering, changing reflections, like opal. 
Opaque Not see-through. 
Organic coating The paint film of a pre-painted metal product or a laminate film of a laminated metal product. 
Overflow An additional or alternative outlet for a gutter, spouting, rainwater head, or sump to harmlessly dispose of abnormal rainwater runoff or caused by blockages of the primary outlet. 
Oversized Hole A larger than normal hole to allow for expansion or other reasons. When required, it is to be made using a 9 mm drill unless otherwise specified. 
Oxide A chemical compound of oxygen and metal that will form as a film on the surface of metals on exposure to the atmosphere. 
Pan The flat portion between the ribs of a profiled metal sheet. 
Pan fixing The fixing of cladding through the flat pan, used when fastening wall cladding, stressed skin, and composite roof cladding. 
Pan Roof A standing seam roof may be called a pan roof.standing seam roof
Parapet The part of a perimeter wall immediately adjacent to the roof, and which extends above it. A parapet higher than one metre is termed a parapet wall.(incorrectly) enclosed balustrade wall
PascalPaA unit of measure equalling one Newton per square metre 
Patina A thin, visible, stable film of oxide, carbonate, or other chemical reaction coatings which forms on the surface of metal on exposure to the atmosphere. 
Peening The permanent deformation or working of metals using a ball-peen hammer. 
Penetration A projection through a roof or wall; e.g., vent pipe, air-conditioning unit window, or doorway.protrusion
Penultimate The next to last or the one before the last one. 
Perforation Deterioration of metal due to corrosion or erosion that results in a hole. 
Performance Quantitative and qualitative criteria which a product or system has to achieve to comply with the NZBC or other relevant Standards. 
Permanent ponding When free water is evident for more than three days in spouting, gutters or on roof or wall cladding. 
Permeability The measure of the rate of a porous material to permit gas or liquid to move through it in a unit time, area, and pressure. It depends on the density of both materials and the temperature. 
Permeable membrane An underlay or other sheet material that permits the passage of water vapour.breather type; permeable underlay.
Personal protective equipmentPPESafety equipment that is personal to the employee or the person to whom it is issued; e.g., safety boots, gloves, earplugs, etc. 
pHpHA 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 (1) The slope or rake of a roof expressed in degrees from the horizontal or as a ratio of vertical height to horizontal distance, e.g., 1 in 20 = 3°. Also known as fall, and the tangent of the pitch angle.
A roof is described by its pitch:
(a) Less than 5° is flat.
(b) From 5° to 10° is low pitched.
(c) Roofs from 10° to 30° is pitched.
(d) A slope of 30° to 60° is steep-pitched.
(e) Over 60° is known as Elizabethan.
Pitch (2) The distance between the centres of two ribs. 
Pitch (3) The distance between threads of a screw, usually expressed as Threads Per Inch (tpi) 
Pitched roof A roof with a slope between 10° and 30° with a ridge at the highest point. 
Pittsburgh lock A type of seam used to interlock two pieces of metal together.lock- formed seam.
Plans and Specifications Drawings, written requirements and other related documents according to which a building is to be constructed or altered. 
Point load A load, normally downwards, applied either permanently or temporarily to a defined specific section of cladding 
Polycarbonate A clear thermoplastic polymeric resin, formed into matching roof and wall cladding profiles, or curved flat sheeting used to provide natural roof lighting. 
Ponding Any free undrained water retained for more than three days after cessation of flow on roof cladding, flashings, or a gutter due to insufficient fall. It can also be caused by permanent deflection or deformation of a roof. 
POP® Rivets Pop rivets are typically used with sheet metal to securely connect two more components. It is a registered trademark owned by Stanley Engineered Fastening. 
Pre-curved A metal cladding profile that is curved off-site, by progressive forming through a pyramid roll or crimp-curve machine. 
Pre-painted Base metal strip or sheet, in line painted to give protection or aesthetic appeal prior to subsequent forming, shaping or fabrication.prefinished; pre-coated.
Pressure coefficient A ratio of the pressure on the surface area of a structure to the free dynamic pressure of the wind. It depends on the size, shape, height and the location of the building and the number and position of its openings.Pressure Factor (internal, external, local, positive and or negative)
Pressure equalisation A design of penetration flashing that relies on the complete inner seal of the penetration between it and the frame. A partial pressure equalisation design is termed pressure moderated. 
Producer statement A detailed statement made by a manufacturer, designer or installer, about the durability, installation and performance of a product or building system, and which claims all manufacturing, design and installation will be or has been carried out in accordance with specific requirements. 
Product Certificate A renewable certificate issued by an accredited certifier for a period of three years certifying the product, when used within its scope of use and installed under specified conditions, complies with Building Code requirements.BRANZ appraisal; third party certificate; codemark
Profile The cross-section of metal cladding, generically known as corrugated (sinusoidal), trapezoidal (ribbed), trough, tray, or standing seam.corrugated (sinusoidal); ribbed (trapezoidal); troughed; boxed or tray
Profiled sheeting Metal sheeting produced with corrugations or ribs to increase its strength.long run
Profiled Washer A metal washer formed to match the ribs of profiled sheeting to support the sheeting at the fastening under high wind loads.Also see: Load Spreading Washer
Pucker The unacceptable distortion of metal flashings due to an incorrect fit. 
Pull-out 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.Pull-through
Pull-up stop-end An end closure of the pan of profiled cladding formed without cutting the ribs and forming pig lugs. 
Purlin A horizontal secondary structural member supporting roof cladding. 
PVCPVCA clear or opaque polyvinyl chloride thermoplastic resin, formed into matching cladding profiles to provide natural roof and wall lighting, and rainwater goods. 
Quarter-round A spouting or eaves gutter with a straight back, and a cross-section of a quarter segment of a circle.quad; D
Radiation: The transmission and emission of infra-red energy in the form of electromagnetic waves. 
Rafter A sloped primary structural member that extends from the ridge to eave designed to support secondary members and the roof cladding. 
Rain collar A conical flashing fitted over a pipe to weather the penetration.rain hat; chinese hat; boot flashing
Rainwater goods Any building product used for rainwater disposal including downpipes, rainwater heads, sumps, spreaders, eaves gutters, spouting, and valleys. 
Rainwater head An external box designed to collect rainwater from a gutter.rainhead
Red rust The formation of a reddish-brown oxide on the surface of steel or iron.corrosion; rust; cancer
Raking Spouting Spouting that runs at an oblique angle to the roof. 
Reglet A system of flashing between a wall and a roof that consists of a primary flashing and a counter flashing to provide additional weather protection. 
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. 
Return period The average number of years within which a given wind gust or rainfall is expected to be equalled or exceeded.ARI; average return interval
Return stopend The end of a spouting or gutter that has the profile face carried around the stopped end. 
Rib A longitudinal up-stand produced by roll-forming, folding or crimping to strengthen or stiffen metal cladding. crest upstand
Rib cap A small metal flashing to weather a rib at a change of pitch.prickles; sharks teeth; end cap; profile end
Ridge (a)  A long crest or chain of hills with sloping faces.
(b) The top of a ridging or profile.
(c) The level intersection point of two opposing planes of roofing.
Ridge cap (a) A small capping to weather the join in the ridging used at a change of pitch or direction on metal cladding.
(b) A formed metal tile used at a ridge.
(a)        Hip-cap.
Ridge vent: A prefabricated ventilator used in lieu of ridging that allows the escape of warm or moist air from a building.vent-ridge.
Ridging A metal flashing, roll topped, square or otherwise strengthened, which can be plain or soft-edged, used to cover the joint of the roof cladding at the ridge, apex, or hip-end. 
Roll A piece of shaped timber used in fixing fully supported roof or wall cladding. 
Roll curved Symmetrical cladding profile that is curved off-site by progressive forming through a pyramid roll machine. 
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.long run
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.roofing
Roof light Translucent profiled GRP, Polycarbonate or PVC cladding, or glass inserted into a roof surface provide natural lighting.skylight; roof window; clear sheet
Roofer A person who covers a roof. 
Roofing The act of constructing or covering a roof.roof
R-ValueRR-values rate how much heat loss the material resists from passing through it; U-values rate how much heat the component allows to pass through it. R-values rate one single material while U-values measure entire components. For example, R-values measure how much heat loss passes through fibreglass insulation while U-values rate how much heat can pass through a window component (glass, air, vinyl sash).
Typical insulation might have an R-value of 19 while a window might have a U-value of 0.35.
R = 1/U. So a U-value of 0.35 would equal an R-value of 2.86. As you can see from this example, windows have a MUCH lower R-value than a properly insulated wall.
Saddle (a) A shaped piece of metal used to weather the junction between a horizontal and vertical surface.
(b) A small metal support used to reinforce a damaged rib on the rib of roof or wall cladding.
Safety edge A small edge turned at 180° on the cut edge of a metal component in order to avoid personal or property damage.hem
Safety harness An assembly of interconnected shoulder and leg straps used where a person could fall from a height.fall arrest harness
Safety mesh A safety wire netting used to prevent workers from falling through a roof. It can also function as an underlay supportunderlay support
Sarking Timber boards or plywood fastened to rafters, trusses or purlins as roof support for metal cladding. 
Sawtooth 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. 
Scotch Ridge The termination of a lower ridge where it meets the intersection of two valleys. 
Screw gun An electric or battery driven driver, with a torque limiting or depth limiting device, used for driving self-drilling, self-tapping screws or other types of screw. 
Scupper A horizontal opening in the side-wall of a gutter, spouting, parapet wall, or enclosed balustrade to allow drainage. 
Sealant A single- or multi-component polymeric material used to waterproof metal joints, in conjunction with mechanical fasteners. 
Sealing washer A rubber EPDM or neoprene washer, sometimes metal-backed, assembled on a fastener and used to prevent water from entering through a fastener hole.metal-backed washer 
Seaming A method of joining two separate sections of metal by mating their two interlocking parallel edges, variously described as lock-formed, grooved, lock-seam, Pittsburgh lock, single and double welt, snap-lock, or knocked-up.Lock-formed; grooved; lock-seam; Pittsburgh lock; single and double welt; snap-lock; knocked-up
Secret flashing A flashing hidden from view or embedded within a wall or wall cavity. 
Secret gutter 

An internal gutter that runs at an oblique angle to the roof pitch. This is commonly found where a roof runs into a raking wall or barge.

Secret valley gutter
Secret-fix A roof or wall cladding system that has no visible or exposed fixings.clip fix; hidden fix
Section properties Values assigned to specific profiles determined by their geometrical shape. 
Secure footing The ability of a person to walk safely, without assistance, on a roof with a pitch smaller than 35°, being dependent on the type of shoes worn and the type of surface. 
Self-drilling screw A fastener that drills and taps its own hole.TEK® screws; drill bit screws
Self-tapping screw A fastener that self-threads when turned into a previously drilled hole; not the same as a self-drilling screw. 
SED Wind Zone Specific Engineering Design Wind Zone as defined by NZS 3604. 
Shake (a) A shake is a basic wooden shingle made from split logs.
(b) An interlocking coated metal tile, impressed to resemble timber shakes.
Shank The original diameter of a nail, screw or bolt before heading, threading, or deformation. 
Shear The scissor action of any tool used to cut metal. 
Shear force A force that causes deformation by producing an opposite but parallel sliding motion. 
Shed roof A lean-to roof having no hips or valleys and containing only one sloping plane. 
Sheeting Any metal, GRP, or plastic roof or wall cladding. 
Shingle (a) Thin, tapered pieces of wood primarily used to cover roofs and walls of buildings. Today shingles are mostly made by being cut, which distinguishes them from shakes which are made by being split out timber.
(b) An interlocking coated metal tile, impressed to resemble timber, composition or modified bitumen shingles.
Shoe A downpipe angle at the discharge point.elbow
Side lap fixing The system by which one sheet is fixed to an adjacent sheet through the side of their lapping ribs. 
Sill flashing A flashing at the bottom of a window or door opening or penetration.tray flashing
Sinusoidal A profile shaped with a series of arcs of a circle resembling part of a sine curve. When these are symmetrical about a centre line they are known as corrugated. 
Skew A roof or fastener at an angle or out of square. 
Skew nailing A method of driving nails in at an angle to the surfaces being nailed. 
Skillion roof A pitched roof with the ceiling fastened and installed at a parallel pitch to the roof. 
Skirt A separate over-flashing used to weather penetration curb flashings. 
Skylight A unit of plastic sheet, glass or an Acrylic dome providing natural light through a roof.roof window
Slip joint An over-flashing fixed to one side only, to allow for expansion. 
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.tin snips; shears
Snow-boards A timber or metal platform built over a gutter to prevent blockage by snow or hail.hail-boards; gutter-boards
Soaker An under flashing, partially hidden, that prevents water ingress by means of hooked edges. 
Soffit The enclosed underside of any exterior eave overhang.eave
Soft Soldering Using a lead/tin alloy that is melted to bond two pieces of compatible metals together at approximately 200°C;soldering
Soft-edge A compatible soft metal edging — usually lead, aluminium, or composite material — seamed onto flashings to provide a closure to profiled cladding and to exclude the weather and vermin. 
Soldering A method of joining metals by forcing melted metal into the joint. 
Sole The bottom surface of a gutter. 
Span The centre distance between two fixing points. The clear distance between two supports is known as the clear span.clear span
Spanbreaker An intermediate supporting member placed under or over roof cladding at a rooflight or a penetration to minimise deflection or traffic damage on large spans.mid-span support
Specular gloss The measure of the reflective surface of an organic film at a defined angle. 
Spiral shank nail A nail having its shank formed with helical grooves so that it rotates when driven.twisted shank
Spouting An external gutter.1/4 round; quad; D; 1/2 round; OG; square
Spreader A downpipe tee or elbow fixed at 90° to the roof slope and used to spread the discharge of stormwater over a greater area of the roof. 
Spring curving An on-site method of installing straight lengths of profiled cladding to a convex or concave substrate.drape curving
Springback The elastic recovery of metal after deformation, which is more pronounced when forming high-strength metals. 
Square Stopping 

When the wall-to-ceiling junction is stopped in the same manner as an internal wall corner junction.  Square stopping can significantly reduce the amount of air and water vapour entering the ceiling cavity from the living areas.

Stainless steel A steel alloy containing a mixture of chromium, nickel and other trace metals to increase its durability. 
Standing seam A fully supported metal roofing system that consists of an overlapping or interlocking seam that occurs at an upturned rib and is made by turning up the edges of two adjacent metal panels, then folding and interlocking them, once for a single seam and twice for a double seam.pan roofing; tray roofing 
Standing seam profile 

A form of tray roofing installed on solid sarking, using traditional seaming tools.

tray profile
Stand-off clips Downpipe retaining brackets used to align the downpipe between the dropper and discharge sump. Normally they are situated near both ends of the downpipe, with intermediate crackets placed in high traffic areas of where span is greater than 3 m.astragals
Static line A rope, wire or rail secured between two points, to support any fall protection device. 
Steep pitch A roof having a pitch between 30° and 60°. 
Step flashing A flashing that weathers a step in the roof when the rafter length is greater than the length of sheeting that is available or advisable.waterfall joint
Stepped flashing A short sloping apron over-flashing set into a wall chase in brick, weatherboard, or block construction. 
Stop end 

(a) That part of a trough of a sheet turned up at the high end of a run. Can be "pulled up" or "dog-eared".

(b) Termination closure at the high or low end of a flashing.

(b) An end closure for a gutter, spouting or flashing.

Stressed skin A term applied to roof or wall cladding that serves as a structural bracing diaphragm for a building. 
Strip Flat metal, over 0.15 mm and under 3 mm thick, of any length and width — usually supplied in a coil. 
Strippable film A plastic film applied to the surface of a metal sheet or strip to give temporary protection to the finish. It must be removed before prolonged exposure to sunlight. 
Subcontractor A person or company who enters into a verbal or written agreement to perform specified work with the main or another contractor. 
Substrate (a) The metallic surface to which a metal, organic or laminated film finish is applied.
(b) The surface upon which the roof cladding is applied or fixed.
Sump An internal rainwater head used to connect a gutter to downpipes. 
Swage A small raised flat rib in a sheeting profile used to minimise distortion caused by centre fullness, or residual or other stress in the sheeting.stiffener
Swarf Fine metallic filings or chips produced as debris from drilling, cutting, or grinding metal on a roof. 
Sweat (a) Visible water droplets as condensation on a smooth surface such as metal sheeting.
(b) A technique of soldering or brazing by the application of sufficient heat to fill the lap gap by capillary action with soft or hard solder.
Swiss Gable A gable roof in which the length of the ridge is longer than the eaves line.  Prow; Flying Gable
Symmetrical profile A profile that has the same configuration on opposite sides of a horizontal centre axis line. 
Synthetic building paper A synthetic roofing or wall cladding underlay. 
Tab A small folded angle or projecting flap formed on a flashing to provide fixing. 
Tag-line A rope that is used to guide a free-swinging load from a crane. 
T-bend The internal bend diameter expressed in terms of thickness used to define the external radius; i.e., 6 T bend = 4 T radius. 
Tek® Screw A proprietary name owned by Buildex for their self-drilling roofing screws for fastening into steel. Often misapplied to other manufacturer’s steel fastening roofing screws and roofing screws generally. The name should not be used generically as that is misleading.self-drilling screws
Temper A hardness condition of metals, determined by a manufacturing process or subsequent annealing. 
Tensile strengthUTSThe tensile limit when metal breaks under load, measured by the load divided by the original cross-section and expressed in MPa. (megapascals).ultimate tensile strength
Terrain The surface roughness of the ground described by its openness or by obstructions such as trees and buildings that influence wind speed. 
The New Zealand Building CodeNZBCThe legal performance requirements as prescribed in the Building Act for building controls within NZ. 
Thermal conductivitykThe 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. 
Tinman's Rivet A small-headed solid fastener, suitable for peening requiring access to both sides.  
Topography The hills, valleys and plains that strongly influence and accelerate wind flow patterns and the wind design load on a structure. 
Tornado A violently rotating column of air attached to the base of a convective cloud descending to the ground and often observed as a funnel. 
Total coated thicknessTCTThe measure of the total of the base metal thickness, plus any additional metal or organic coating. 
Trade practice Trade habits used by members of an industry, known variously as acceptable, good and bad. 
Trade training Tuition given to a trainee or workman by a qualified tradesman. 
Tradesman A workman or woman, having spent a prescribed period of time working at a trade; and who has been qualified by the successful completion of written and practical trade examinations. 
Translucent Allowing light to pass through, but not transparent. 

Clear, can be seen through.

Transverse A flashing or fastenings running horizontally across the sheeting. 
Trapezoidal Profiled roof or wall cladding with longitudinal ribs angled similarly to a trapezoid.rib profile
Tray The flat draining area of a roof. 
Tray profile A predominantly flat, secret fixed profile typically with one tray per sheet and narrow ribs which are locked together by frictionstanding seam profile
Trough The flat draining are of a roof.trya
Trough profile A predominantly flat, secret fixed profile; typically with two or three trays per sheet.decking, secret fixed
Turn-up tool A hand tool used to form stop-ends or to turn down the ends of metal cladding.stop ender
Undercutting The corrosion of a metal substrate under a paint film, caused by a score mark, edge or hole.edge creep
Underlay A flexible membrane laid under roof or wall cladding to control condensation or provide reflectivity.building paper
Uniformly Distributed LoadUDLUsed as a measure of the wind load on metal cladding, usually expressed in kPa (kilopascals). 
Unwashed Areas of roof or wall cladding protected from washing by natural rainfall at an angle of 45° by a projecting roof or overhang. 
Upstand The vertical face of a flashing or stop end. 

R-values rate how much heat loss the material resists from passing through it; U-values rate how much heat the component allows to pass through it. R-values rate one single material while U-values measure entire components. For example, R-values measure how much heat loss passes through fibreglass insulation while U-values rate how much heat can pass through a window component (glass, air, vinyl sash). Typical insulation might have an R-value of 19 while a window might have a U-value of 0.35.

R = 1/U. So a U value of 0.35 would equal an R-value of 2.86. As you can see from this example, windows have a MUCH lower R-value than a properly insulated wall.
Valley A gutter at the intersection of two sloping areas of roof that meet at an oblique angle. 
Vapour barrier A sealed impermeable membrane designed to eliminate the passage of water or water vapour.vapour check
Vapour control layerVCLAn impermeable membrane designed to minimise the passage of water or water vapour.vapour check; vapour retarder
Vented A cavity that provides some degree of water vapour diffusion and air movement. 
Ventilated A cavity that has been designed to provide a significant flow of air or water vapour to the outside air, such as a ventilated ridge. The NZBC allows for drained, but not vented wall cavities. 
Walkway A permanent or temporary structure placed over metal roof cladding to enable access without causing damage or imposing a point load on the
WANZ-WIS The Window Association of New Zealand's Window Installation System. 
Watershed A penetration over-flashing type that extends to the ridge.back flashing; dry pan flashing
Weather: (a) The state of the atmosphere at a given time and place, specified by variables including, wind velocity, humidity, temperature and pressure.
(b) To cause a roof or flashing to shed water.
Weathering The visible change in a surface, such as the oxidation of metals, or chalking of pre-coated materials, due to atmospheric exposure.Weathered
Weatherproof (a) The ability to withstand exposure to weather without damage.
(b) To protect a building from the elements.
Weathertightness The degree of protection offered from the elements. 
Web The vertical or near-vertical part of a rib. 
Welt (a) An interlocking metal seam used when site fabricating roof sheeting.
(b) Folds on flashings or roof cladding joining two adjacent metal sheets together at their edges without fasteners.
single welt; double welt; cross welt
Wet storage stain Corrosion effects due to condensation or rain penetration of nesting profiles. Also known as White Rust for galvanised, Black Rust for Aluminium Zinc coating, and Black Stain for Aluminiumwhite rust; black rust
White rust The visible white corrosion product found on galvanised coatings in protected, unwashed, cut edges or micro-cracked areas.bloom
Wicking 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. 
Workman A man or woman employed in a trade, who is or has learned trade skills from their employer, supervisor or a technical institute. 
Yield point The first stress point at which some metals will plastically and permanently deform. 
Yield stress The recorded stress at the point of yielding. 
Zinc aluminium coating: Steel protected against corrosion by a zinc dominated zinc/aluminium alloy.ZA; Galfan or Galvalloy