Roofing A to Z

A comprehensive guide to roofing terms

If you want to know the difference between a ‘Joggle’, a ‘Pigs Lug’ and a ‘Secret Flashing’, then this is the page you want. To say we are obsessed with roofing would be an understatement. While some of you won’t be interested in the following roofing terms, others just might find it as fascinating as we do.

Accessories:
Gutters, ridge capping, ventilators, flashings, downpipes, brackets and their fixings.
Absorption:
The ability of a material to accept within its body, quantities of vapour or liquid, such as moisture.
Acceptable solution:
A prescriptive means of compliance with the performance requirements of the NZBC, approved by the Department of Building and Housing.
Acceptable trade practice:
The minimum standard of design and workmanship to comply with the performance requirements of the NZBC.
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:
Aluminium zinc coating. A continuously hot-dipped coating used to protect steel against corrosion consisting of
45% zinc and 55% aluminium by mass. Also known as AZ, Zincalume® Galvalume,
Aluzinc:
Aluzinc or Duralume generally conforming to AS/NZS 1397.
Anneal:
To soften a metal by heating, to restore or increase it’s ductility.
Annular grooved nail:
A nail having a shank deformed with a series of circular grooves.
Anodic:
When two metals are connected in moist or wet conditions, galvanic corrosion can
occur. The anodic metal, being the anode (-), is sacrificed 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. Also known as postform painting.
Approved:
Any documentation, solution or method that is accepted by a recognised authority.
Apron:
A near horizontal flashing with a vertical upstand that prevents ingress of or sheds
water from a higher wall or roof onto a lower roof.
Astragal:
A metal strap used to fasten downpipes to a wall.
Asymmetrical profile:
A profile that has a different configuration on opposite sides of the horizontal centre
axis. The opposite to symmetrical.
Awning:
A roof cantilevered and projecting from a building. Also known as a Canopy.
Baby Iron:
A miniature corrugated profile rolled with 6mm high ribs. Also known as sparrow iron,
mini-corrugate, and mini-iron.
Backer coat:
An organic coating on the reverse side of a prepainted strip or coil, not intended for
external exposure.
Backout:
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 edge of the roof cladding at the gable end of a roof. Also
known as barge roll, cover roll, ridge roll, barge mould and square barge.
Base metal thickness: (B.M.T.).
The thickness of the bare or base metal before any subsequent coating,
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. Also
known as counter-batten.
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 rod.
Bend radius:
The formed outside radius on a flashing or sheeting that is acceptable for the design
end use.
B.C.A:
A Building Consent Authority which is accredited by the DBH to issue building
consents.
Bossing:
The working of a malleable metal into a required shape, by the use of wooden or
plastic tools. Also known as Dressing.
Boot flashing:
A proprietary EPDM prefabricated flashing used to weatherproof circular pipes.
Box gutter:
A square or rectangular internal gutter between two roof surfaces or at a parapet wall.
Brazing:
The joining of metals by the high temperature application of an alloy having a lower
melting temperature than any of the metals to be joined.
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.
Brittle roofing:
Flat, troughed or corrugated plastic or other sheeting, that is or can become brittle.
Buckling:
A loss of the original shape of shaped metal, by compressive bending, bearing or shear
loading. Also known as a Kink, Ding, Wrinkle and Bulge.
Bullnose:
A shaped piece of roof cladding, curved near to a quarter circle on its outer end, and
used predominately as verandah roof sheeting.
Building Consent Authority:
A territorial Authority or Building Certifier accredited to issue building consents, make
inspections and certify Code compliance. Also known as a BCA.
Building paper:
An absorbent permeable membrane made from treated kraft paper placed under roof
or wall cladding. Also known as Permeable Underlay.
Butterfly roof:
A structure having two inward sloping roofs, draining to a centre gutter.
Butt strap:
A soaker underflashing used as an expansion joint.
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.
Canopy:
A cantilevered roof without walls over a doorway. Also known as an Awning.
Canterbury prickle:
A small shaped capping to a roof rib at a change of pitch.
Capillary:
The action that causes movement of moisture by surface tension between two surfaces
in close contact. Also known as Capillary action, Capillary attraction and wicking.
Condensation:
The process by which a vapour such as water vapour changes phase to a liquid. Also
known as 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. Also called roof fixer.
Convection:
The transport of heat within a gas or a fluid by the relative movement of those parts
that differ in density.
Corrosion:
The reaction of a material with its environment or incompatible materials, that causes
measurable alteration, which can impair its performance.
Corrugate:
A profiled sheet formed into a series of sinusoidal or circular curves. Also known as
corrugated iron.
Counterbatten:
A spacer of timber or steel fixed to a purlin or batten, which provides an air space
between the cladding and any insulation or safety mesh.
Cover:
(a) The net width of sheeting less the lap. Also known as Effective Cover.
(see drawing 1.4.3.)
(b) The net width of a flashing that covers the sheeting.
Creep:
The metal deformation, or a change in shape that increases continuously when under
constant load or stress.
Crest:
The top surface of a rib. Also known as a Crown. (see drawing 1.4.3.)
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. Also known as a Raised Curb.
Crimp curving:
A method of forming a curve on profiled sheeting by discrete indentations.
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. Also known as a kerb.
Cyclonic winds:
Strong winds rapidly spiralling clockwise into a centre of low pressure in the Southern
hemisphere. Also known as a Hurricane or a Typhoon.
DBH:
A government department dealing with all legal matters pertaining to Building and
Housing.
Decking:
A predominantly flat profile roof or wall cladding, also referred to as Tray.
Deck:
The substrate of a structure that supports claddings that require to be fully-supported.
Deflection:
The deviation from a straight line induced by a load or action.
Deformed shank nail:
Nails with annular, spiral or otherwise deformed shanks. Also known as Enhanced
shank nails.
Depth:
The vertical height of a rib or gutter.
De-indexing:
he releasing of interlocking profiled sheets.
Design wind load:
The site design wind pressure in kilopascals (kPa) on a specific part of a structure,
modified by pressure coefficients.
Design wind pressure p:
The pressure in pascals (Pa) obtained by multiplying the design wind speed
(Vdes in m/s) by the formula: p = 0.6Vdes
2 Pa
Design wind speed Vdes:
The wind region speed in metres per second adjusted for annual probability of
exceedance, wind direction, geographic position, surrounding environment and
height.
Dew point:
The temperature at which water vapour condenses, which varies with the relative
humidity and the pressure.
Ding:
A permanent creasing of a rib or sheet, usually due to damage on a roof, resulting in
structural depreciation, and consequent inability to comply with performance
requirements.
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.
DoL:
An acronym of the Department of Labour, formerly known as OSH.
Dog ear:
A three dimensional box like internal corner formed in metal without cutting. Also
known as Pig’s Lug.
Decking:
A predominantly flat profile roof or wall cladding, also referred to as Tray.
Dominant opening:
An opening in the external surface of a closed building which directly influences the
internal wind pressure.
Dormer:
A roofed window structure projecting at right angles from a sloping roof surface.
Downturn:
That part of the trough of a sheet turned down into a gutter. Also known as
Turndown.
Downpipe:
A pipe used to carry roof water from gutters and roof catchments to drains or storage
tanks. Also known as Downspout.
Drape curving:
The use of metal cladding to cover a curved roof, using its own weight and not being
pre-curved. Also known as Spring Curving.
Dressing:
The operation of flattening or beating metal into the required shape,
Drip:
(a) An outward projecting edge formed on a metal flashing, to direct water away from
the building or to avoid capillary action. Also known as Birds beak, Tip, Kick, or Break.
(b) A step or break in a roof or gutter, across the direction of fall.
Dropper:
A spouting or gutter outlet. Also known as a Pop.
Dry film thickness:
The thickness of a cured organic coating applied to a metal substrate.
Ductility:
The ability of metal to withstand distortion without fracture.
Duopitch:
A roof having two differing sloping pitches.
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.
Dutch gable:
A type of roof frame that is partially hipped but which terminates as a gable.
Dynamic pressure:
The potential pressure available from the kinetic energy of the effective wind speed.
E2/AS1:
An Acceptable Solution to the NZBC clause E2 External Moisture issued by the DBH.
Eaves:
The protruding edge of a roof slope. When enclosed is known as a soffit.
Eaves gutter:
An external roof gutter attached to a roof overhang or the lower edge of a roof. Also
known as Spouting.
Edge protection:
A guardrail or restraint designed to prevent a person reaching over a roof edge or
falling from a height.
Elastic limit:
The limit within which, when a material is stressed under load, no noticeable or
measurable permanent set or deformation occurs.
Elevation:
The part of a drawing which shows the front, side or end view of the wall or structure,
giving details of roof slope and openings.
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, when an electric current passes through it,
produces an electrochemical reaction.
Electrolytic corrosion:
Galvanic corrosion commonly resulting from the contact of two dissimilar metals when
an electrolyte, such as water, is present.
Electrochemical series:
The order in which metals react with one another in an electrolye, with the
electronegative metal corroding in preference to the electropositive metal. Also known
as Electromotive or Galvanic Series.
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.
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.
Escarpment:
A steeply sloping face separating two relatively level plains, where the plains average
slope is <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. Also known as Sawtoothing.
Fascia board:
A vertical board fixed to the bottom of the rafters 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. Also known as Fixings.
Fatigue:
The condition that induces weakness or cracking in a metal component by continued
fluctuating stress, resulting in fracture.
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. Also known as foam seal.
Film thickness:
The thickness of a paint or other coating usually expressed in microns.(μm). Wet film
thickness is the thickness of a coating as applied. Dry film thickness (DFT) is the
thickness after curing.
Fixing:
The method of attachment of cladding to the frame achieved by the use of fasteners.
Flashing:
A metal covering, built in to prevent moisture movement or the ingress of water to the
inner parts of a building. 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.
Described variously as Apron, Barge, Back, Capping, Corner, Curb, Overcloak, Raking,
Ridge, Secret, Sill, Skirt, Soaker, Soft-edge, and Stepped.
Flame retardant:
A material to which a substance has been added to reduce or retard its tendency to burn.
Flat roof:
A roof having a slope between 0˚ and 5˚.
Flux:
A chemical liquid or substance used to clean and remove any oxide or other film from a
metal, prior to soft or hard soldering or brazing.
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.
Folding:
A manufacturing method used to permanently deform metal over a small radius to a
desired angle. A similar method is known as Brake Pressing.
Free roof:
A roof without enclosing walls e.g. a carport.
Fretting:
Damage to a metal surface or coating between adjacent surfaces, caused by movement
and friction, e.g. during transportation.
Fully supported cladding:
Metal cladding that requires a solid substrate to provide strength for wind or point
loads. Also known as tray roofing.
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.
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)
Galvanised steel:
Steel protected against corrosion by a hot-dipped zinc-coating described as Z.
Gambrel:
A roof that has two pitches on each side. Similar to a Mansard roof.
Gauge:
The thickness of metal described in mm or inches, previously known as a gauge nonmeasured
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.
G.R.P:
Glass fibre reinforced polyester translucent or opaque sheeting, used for roof lighting
and manufactured to match profiled sheeting.
Groover:
A hand tool used for seaming sheet metal. Also known as a Seamer.
Gutter:
A channel formed to collect and carry water away from a roof, variously described as
internal, external, box, eaves, valley, and secret.
Half-round :
A spouting or eaves gutter having a half circle cross-section.
Head flashing:
A flashing at the top of an opening or penetration.
Hem:
A flat but open metal edge folded 180˚. Also called a safety edge.
Hertz:
A 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.
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 pin hole or area where a liquid applied paint coating or laminate film material
is missing.
Hook:
An open hem used on a hidden underflashing, 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. Also known as a 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.
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. Also known as a Crank.
Kilonewton (kN):
A metric or SI unit of force, used to measure point or live loads. 1000N = 1 kN
Kilopascal (kPa):
A metric or SI square unit of pressure, used as a measure for wind loads.
1 kPa = 1 kN/m2
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. (see drawing 1.4.3.)
Lap tape:
An adhesive strip made from UV resistant materials used as a joint sealant or part of a
roof system.
Lean-to:
A monopitch or single slope roof attached to another structure but at a lesser pitch.
Also known as a Shed Roof.
Leeward:
The opposite direction to that from which the wind is blowing (windward). The side
sheltered from the wind.
Licensed Building Practitioner:
A person issued with a renewable licence having satisfied the Building Practioners
Board that he or she meets the minimum standard of competence for each class of
licence. Also known as a LBP.
Lightweight roof:
A roof cladding which has a mass not exceeding 20kg per square metre.
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.
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.
Load spreading washer:
A metal washer formed to match the ribs of profiled sheeting to provide support to
the sheeting at the fastening under high wind loads. Also known as a Profiled Washer,
Cyclone Washer or a Top Washer.
Local pressure coefficient:
A factor applied to the design wind load due to the dynamic increase of the wind
around the periphery of walls or roofs. Also known as kl and 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 15˚.
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.
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 steels, aluminium, stainless steel, copper and zinc.
Micro-climate:
The climate of a small specified area, e.g. under eaves, near the sea shore 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.
Micrometre:
A millionth of a metre, used as a measure of the thickness of metallic and organic
films. Also known as a Micron μm.
Monel:
An alloy of 55% copper and 45% nickel used as rivets, fasteners or clips.
Monopitch:
A roof having one constant slope with no ridge, also known as mono-slope or lean-to.
Nesting profiles:
Cladding profiles that closely stack together.
NZBC:
The New Zealand Building Code. The legal performance requirements as prescribed in
the Building Act for building controls within N.Z.
Netting:
An open weave lightweight material used under roof cladding as a support for underlay
Neutral-cure silicone:
A sealant used to join metal that has a neutral pH and does not corrode metal.
Night sky radiation:
A phenomenon where a roof by radiating heat to a clear night sky, can become up to
5˚C colder than the ambient temperature.
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˚.
O.G. (OGee):
‘Old Grecian’. A shape of convex and concave curves used in spouting. Also known as
Old Gothic.
Oil canning:
Distortion in the form of waviness or centre fullness in a profiled sheet. Also known as
‘Canning’ or ‘Panning’.
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, rain water head or sump to
harmlessly dispose of abnormal rainwater runoff, or caused by blockages of the
primary outlet.
Oxide:
A chemical compound of oxygen and metal that will form as a film on the surface of
metals on exposure to the atmosphere.
pH:
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.
Patina:
A thin stable film of oxide, carbonate or other chemical reaction coating, which forms
on the surface of metal on exposure to the atmosphere.
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.
Pan:
The flat portion between the ribs of a profiled metal sheet. (see drawing 1.4.3.)
Pan fixing:
The fixing of cladding through the flat pan, used when fastening wall cladding,
stressed skin, and composite roof cladding.
Peening:
The permanent deformation or working of metals by the use of a ball peen hammer.
Penetration:
A projection through a roof or wall e.g. vent pipe, air-conditioning unit window or
doorway. Also known as a Protrusion.
Penultimate:
The next to last or the one before the last one.

Quantitative and qualitative criteria which a product or system has to achieve, to
comply with the NZBC or other relevant Standards.
Perforation:
Deterioration of metal due to corrosion or erosion that results in a hole.
Permanent ponding:
When free water is evident for more than three days in spouting, gutters or on roof or
wall cladding.
Permeable membrane:
An underlay or other sheet material that permits the passage of water vapour. Also
known as Breather type or Permeable Underlay.
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.
Personal protective equipment:
(P.P.E.) Safety equipment that is personal to the employee or the person to whom it is
issued. e.g. safety boots, gloves, ear plugs etc.
Pitch:
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. (see section 15.2)
A roof is described by its pitch:
(a) Less than 5˚ is Flat,
(b) 5˚ to 15˚ is Low-pitched,
(c) 15˚ to 30˚ is Pitched,
(d) 30˚ to 60˚ is Steep-pitched,
(e) Over 45˚ is known as Cathedral
(f) Over 60˚ is defined as a Wall.
The distance between the centres of two ribs. (see drawing 1.4.3.)
Pitched roof:
A roof with a slope between 15˚ and 30˚ with a ridge at the highest point.
Pittsburgh lock:
A type of seam used to interlock two pieces of metal together. Also known as a 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 used in a testing regime as a measure of the ability of roof or wall cladding to
support a person with a bag of tools, at mid span. (1.1kN)
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, or to permanent deflection
or deformation of a roof.
Pre-painted:
Base metal strip or sheet, in line painted to give protection or aesthetic appeal prior to
subsequent forming, shaping or fabrication. Also known as Prefinished or pre-coated.
Pre-curved:
A metal cladding profile that is curved off-site, by progressive forming through a
pyramid roll or crimp-curve machine.
Pressure coefficient:
A ratio of the pressure on the surface area of a structure to the free dynamic pressure
of the wind. It is dependent on the size, shape, height and the location of the building
and the number and position of its openings. Also known as Pressure Factor, and
variously described as 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 any work 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.
Profile:
The cross-section of metal cladding, generically known as corrugated (sinusoidal),
ribbed (trapezoidal), troughed, boxed or tray.
Profiled sheeting:
Metal sheeting produced with corrugations or ribs to increase its strength.
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.
Pull-up stopend:
An end closure of the pan of profiled cladding, formed without cutting the ribs.
Purlin:
A horizontal secondary structural member supporting roof cladding.
P.V.C.:
A clear or opaque polyvinyl chloride thermoplastic resin, formed into matching
cladding profiles to provide natural roof and wall lighting.
Quarter-round:
A spouting or eaves gutter with a straight back, and a cross-section of a quarter
segment of a circle. Also known as Quad or ‘D’.
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.
Rain collar:
A conical flashing fitted over a pipe to weather the penetration. Also known as a Rain
hat or Chinese hat.
Rainwater goods:
Any building product used for rain water disposal including downpipes, rain water
heads, sumps, spreaders, eaves gutters, spouting and valleys.
Rainwater head:
An external box designed to collect rainwater from a gutter. Also known as a Rainhead
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.
Return period:
The average number of years within which a given wind gust or rainfall is expected to
be equalled or exceeded.
Return stopend:
The end of a spouting or gutter that has the profile carried around the stopped end.
Rib:
A longitudinal up-stand produced by roll-forming, folding or crimping to strengthen or
stiffen metal cladding. (see drawing 1.4.3.)
Ribcap:
A small metal flashing to weather a rib at a change of pitch. Also known as Prickles,
Sharks Teeth, End Cap or Profile End.
Ridge:
(a) A long crest or chain of hills with sloping faces on either side.
(b) The top of a ridging or profile. Also known as crest.
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.
Ridge cap:
(a) A small capping to weather the join in the ridging used at a change of pitch or
direction on metal cladding. Also known as Hip-cap.
(b) A formed metal tile used at a ridge.
Ridge vent:
A prefabricated ventilator used in lieu of ridging that allows the escape of warm or
moist air from a building. Also known as Vent-ridge.
Rivet:
(a) A small headed hollow tubular fastener with an expandable body for joining sheet
metal capable of being fastened from one side. Also known as a Blind or Pop Rivet.
(b) A small headed solid fastener suitable for peening requiring access to both sides. Also
known as a Tinmans rivet.
Roll:
A piece of shaped timber used in fixing fully supported roof or wall cladding.
Roll curved:
A 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.
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.
Roofer:
A person who covers a roof.
Roofing:
The act of constructing or covering a roof.
Roof light:
Translucent profiled G.R.P., Polycarbonate or P.V.C. cladding, used in conjunction with
metal roof cladding to provide natural lighting.
Saddle:
(a) A small metal support used to reinforce a damaged rib on the rib of roof or wall
cladding.
(b) A shaped piece of metal used to weather the junction between a horizontal and
vertical surface.
Safety edge:
A small edge turned at 180˚ on the cut edge of a metal component in order to avoid
personal or property damage. Also known as a hem.
Safety harness:
An assembly of interconnected shoulder and leg straps, used where a person could fall
from a height. Also known as fall arrest harness.
Safety mesh:
A safety wire netting used to prevent workers falling through a roof. It can also
function as an underlay support
Sarking:
Timber boards or plywood fastened to rafters, trusses or purlins as a roof support for
metal cladding that is not itself designed to be self-supporting.
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.
Scupper:
A horizontal outlet in the side-wall of a gutter or spouting to allow drainage.
Sealant:
A single- or multi-component polymeric material used to waterproof metal joints, in
conjuction with mechanical fasteners.
Sealing washer:
A rubber E.P.D.M or neoprene washer, sometimes metal-backed, assembled on a
fastener and which when compressed is used to prevent water from entering through
a fastener hole.
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.
Secret-fix:
A roof or wall cladding system that has no visible or exposed fixings.
Secret flashing:
A flashing hidden from view or imbedded within a wall or wall cavity.
Secret gutter:
A gutter partially or completely hidden from view, used when roof cladding is cut on a
diminishing angle. At roof pitches over 12˚ it is termed a secret valley gutter.
Section properties:
Values assigned to specific profiles determined by their geometrical shape.
Secure footing:
The ability of a person to walk safely on a roof surface without assistance, below a 35˚
pitch, 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.
Self-tapping screw:
A fastener that self-threads when turned into a previously drilled hole.
Shake:
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.
Sheet: Flat metal over .15mm and under 3mm in thickness, of exact length and over 450mm in
width.
Sheeting:
Any metal, G.R.P., or plastic roof or wall cladding.
Shoe:
A downpipe angle at the discharge point. Also known as an Elbow.
Shingle:
An interlocking coated metal tile, impressed to resemble timber, composition or
modified bitumen shingles.
Sidelap fixing:
The system by which one sheet is fixed to an adjacent sheet through the side of their
lapping ribs, usually required at mid span for cladding with large purlin spacings.
Sill flashing:
A flashing at the bottom of a window or door opening or penetration. Also known as
a 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 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 to the rafters at the roof angle.
Skirt:
A separate overflashing used to weather penetration curb flashings.
Skylight:
A unit of plastic sheet, glass or an Acrylic dome providing natural light through a roof.
Slip joint:
An overflashing fixed to one side only, to allow for expansion.
Soaker:
An under flashing, partially hidden, that prevents water ingress by means of hooked edges.
Soffit:
The enclosed underside of any exterior eave overhang. Also known as an Eave.
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.
Sole:
The bottom surface of a gutter.
Soldering:
A method of joining of metals together by either:
(a) soft soldering: using a lead/tin alloy that is melted to bond two pieces of
compatible metals together at approximately 200˚C
(b) 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.
(c) cold soldering: using a sealant or adhesive to bond two pieces of metal together.
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.
Snow-boards:
A timber or metal platform built over a gutter to prevent blockage by snow or hail.
Also known as Hail-boards and Gutter-boards.
Span:
The centre distance between two fixing points. The clear distance between two
supports is known as the 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. Also known
as 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. Also
known as twisted shank.
Spouting:
An external gutter variously known as 1/4 round, quad, D, 1/2 round, O.G., or 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.
Springback:
The elastic recovery of metal after deformation, which is more pronounced when
forming high-strength metals.
Spring curving:
An on-site method of installing straight lengths of profiled cladding to a convex or
concave substrate. Also known as Drape Curving.
Stainless steel:
A steel alloy containing a minimum of 11% chromium and up to 30% nickel, used in
roof and wall cladding, accessories and fasteners.
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.
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. Also known as a Waterfall joint.
Stepped flashing:
A short apron overflashing set into a wall chase in brick or block construction.
Stressed skin:
A term applied to roof or wall cladding that serves as a structural bracing diaphragm
for a building.
Stop end:
(a) That part of a trough of a sheet turned up at the high end of a roof or wall or the
lower end of a penetration. Can be “pulled up” or “dog-eared”.
(b) An end closure for a gutter, spouting or flashing.
Strip: Flat metal over 0.15mm and under 3mm, of any length and width, usually supplied in coil.
Strippable film:
A plastic film applied to surface of metal sheet or strip to give temporary protection to
the finish.
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 rain water 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. Also known as a stiffener.
(see drawing 1.4.3.)
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.
Symmetrical profile:
A profile that has the same configuration on opposite sides of a horizontal centre axis
line.
Synthetic wrap:
A polymeric building film.
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.
Terrain:
The surface roughness of the ground described by its openness or by obstructions such
as trees and buildings that influence wind speed.
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. (megapascals). Also known as Ultimate
tensile strength. (U.T.S.)
Thermal conductivity:
(k) 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.
Topography:
The hills, valleys and plains that strongly influence and accelerate wind flow patterns,
which alter the wind design load on a structure.
Tornado:
A violent rotating column of air attached to the base of a convective cloud, descending
to the ground and often observed as a funnel.
Total coated thickness:
T.C.T: The measure of the total of the base metal thickness, plus any additional metal or
organic coating.
Tradesman:
A workman or woman, having spent a prescribed period of time working at a trade, who
has been qualified by the successful completion of written and practical trade examinations.
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.
Transverse:
A flashing or fastenings running horizontally across the sheeting.
Trapezoidal:
Profiled roof or wall cladding with longitudinal ribs angled similarly to a trapezoid.
Tray:
The pan, trough or flat draining area of a deck-type of roof .
Tray roof cladding:
A profile having a large flat area compared with the rib or seam. Also known as Deck
Roofing, Trough Roofing and Fully supported roofing .
Turn-up tool:
A hand tool used to form stopends or to turn down the ends of metal cladding.
U.D.L:
A uniformly distributed load used as a measure of the wind load on metal cladding,
usually expressed in kPa. (kilopascals)
Undercutting:
The corrosion of a metal substrate under a paint film, caused by a score mark, edge or
hole. Also known as Edge Creep.
Underlay:
An absorbent permeable membrane that absorbs or collects condensation, or water
that may penetrate the roof or wall cladding. Also known as Building Paper.
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 stopend.
Valley:
A gutter at the internal intersection of two sloping planes of roof cladding where the
roof pitch is 12˚ or greater.
Vapour barrier:
A sealed impermeable membrane designed to eliminate the passage of water or water
vapour.
Vapour control layer.
(V.C.L.): An impermeable membrane designed to minimise the passage of water or water
vapour. Also known as a vapour check or 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.
WANZ-WIS:
The Window Association of New Zealand’s Window Installation System.
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. Also known as a
cat-walk.
Watershed:
A penetration overflashing type that extends to the ridge. Also known as Back Flashing.
Weather:
1. (noun) The state of the atmosphere at a given time and place, specified by variables
including, wind velocity, humidity, temperature and pressure.
2. (verb) To cause a roof or flashing to shed water
Weathering:
(verb) To prevent deterioration, such as the oxidation of metals, or chalking of precoated
materials due to atmospheric exposure. Also known as the intransitive verb
Weathered.
Weatherproof:
1. (adj) The ability to withstand exposure to weather without damage. Also known as
weathertight.
2. (transitive verb) 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:
An interlocking metal seam used when site fabricating roof sheeting. Folds on
flashings or roof cladding joining two adjacent metal sheets together at their edges
without fasteners, variously described as single, double, and 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 Aluminium.
White rust
The visible white corrosion product found on galvanised coatings in protected,
unwashed, cut edges or micro-cracked areas. Also known as 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 Technical Institute.
Wrap:
A synthetic film used as a building membrane and capable of completely enclosing
walls. Also known as Synthetic or Polymeric Wrap.
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 continuously hot-dipped coating of 95% zinc
and 5% aluminium by mass with the addition of Lanthanides. Known as ZA, Galfan or
Galvalloy and generally conforming to EN 10214.

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