Glossary of Terms

Access opening

An opening in a building element, fitted with a removable cover, to allow maintenance of a concealed pipe, fixture or other apparatus.

Access point

A place where access may be made to a drain for inspection, cleaning or maintenance; may include an inspection point, rodding point, inspection chamber or access chamber.


Capable of being reached for the purposes of inspection, maintenance, repair or replacement, but may first require removal of an access panel, cover, door or similar obstruction.


The qualities or characteristics of a room, auditorium, stadium, etc., that determine the audibility or fidelity of sounds in it.

Air venting

Allowing air to enter into or escape from a confined space.

Base metal thickness

The thickness of metal sheeting prior to coating or painting.

Back siphonage

Backflow that occurs when the water supply pressure falls below atmospheric pressure.

Barge cap

Capping for the overhanging end of a gable sheet.


Insulating material such as fibreglass, usually bonded to a reflective foil.

Box gutter

Internal gutter either rectangular or a trough between two sloping roof surfaces or a roof slope and a parapet.

Capillary joint

A joint in which the parts are united by the flow of filler metal by capillary action along the annular space between the outside and inside of a pipe socket or capillary filling.


Metal caps used as a waterproof device where the roof sheeting ends.

Coating class

The degree of corrosion protection. This is directly proportion to the coating mass.

Concealed-fixed deck

A type of decking/roofing. Rather than being fixed onto the roof by screws, the roof decking is locked onto fixing clips that were fastened onto the roof supports.


A fitting used for connecting together other fittings or fixtures.


A polyethylene strippable film which protects the roof and wall sheeting during storage.

Crank (Crimp) curving

Mechanically curving a roof sheet to a tight radii with a series of transverse segments.

Crimp joint

A joint using an internally inserted fitting and an external crimp ring, which is compressed with a calibrated crimp tool or other suitable tool.


Lifting and separating of interlocking roofing sheets.


A pipe to carry roof water from gutters and roof catchments to drains or storage tanks.


Overhang at the lower edge of a roof.


Ethylene Proylene Diene Monomer. A rubber commonly used for washers of fasteners.


The difference in height between two points in the direction of flow.


The member usually fixed vertically to timber or steel around the building covering the joint between the top of a wall and the projecting eaves upon which the rainwater guttering is usually connected.


A fixing arrangement designed to bolt, screw, fasten or otherwise fix or mount products or related items.


A projecting flat rim or disc, with or without bolt holes, for attaching to, or assembling on the end of a fitting.


Sheet metal used to reinforce and weatherproof the joints and angles of a roof.

Gable roof

Duo or two pitched roof with vertical ends.


The thickness or diameter of various, usually thin, objects, such as the thickness of sheet metal or the diameter of a wire or screw.


Horizontal wall member to which the wall cladding is fixed.


A trough fixed under or along the eaves for draining rainwater from a roof.


Inclined projecting angle formed by the junction of the sloping end and the side of a roof.

Hip bracing

A flashing connecting two pieces of curved sheeting.

Hipped roof

Roof with sloping ends and sides.

Inert catchment

Areas where water is trapped due to dents on the roof sheeting. These can cause corrosion and discolouration of the roof.


The result of the joining together of two or more parts of a construction.

Lineal metre mass

Mass per linear metre (kg/m).

Load span tables

A table of maximum spans that the roof sheeting can have without failure occurring considering assumptions or parameters as detailed in AS 1170:2002.

Minimum yield strength

Minimum force/pressure asserted before breaking occurs.

Mobile mill

A system for roll forming concealed roofing profiles on site rather than in a factory to lengths in excess of 100m.

Oil canning

Undulations or waviness on the surface of otherwise flat metal sheets. Prevented by use of stiffening ribs as per HB39:1997.


The part of the roof structure which extends horizontally beyond the vertical plane of the exterior walls of a building.


Any low protective wall or barrier at the edge of a roof or balcony.


Protrusions such as pipes, ducts etc. that pass through the surface of roof sheeting that require flashings.

Pierce (screw) fixed deck

Decking fixed onto the roof by fastening it with screws.


Upward or downward inclination or slope.


Water remaining on roof due to deflection of roof sheeting and/or guttering, a potential source of corrosion.


A horizontal roof member to which the roof sheeting is fixed longitudinally.

Rainfall capacity

See ‘Water carrying capacity’.


An external gutter pit used to connect downpipes to roof gutters and to provide an external overflow point.


The peak of a pitched roof.


See ‘Sisalation’.


A water resistant vapour barrier fixed beneath roof sheeting, commonly as a reflective foil.

Skillion Roof

Mono/single pitched roof.


Conduit built into a structure of a building to allow another profile to pass through, giving protection and allowing for relative movement.

Smooth curving

Mechanically pre-curving roof sheet prior to fixing, achieving a smooth unbroken curve.


The distance between supports of the roof sheeting.


See ‘Gutter’.

Spring curving

Fixing of a roof sheet to a radius without mechanically curving the material.

Step joint

To cover a long roof area, the roof sheeting is joined by overlapping the end of one sheet with the start of another. These overlaps are called step joints. Step joints are undesirable as they collect debris and dust and water may seep through.

Storm water

The run-off due to rainfall from roofed areas, termed roof water, from paved and unpaved areas, termed surface water and from water bearing ground, termed subsoil water.

Storm water system

Comprised of all storm water mains and drainage works vested in the regulatory authority.


Fine metallic filings or shavings made by a cutting tool or drill.


A material underlying a surface coating.


A pit made in a floor, or a sunk below the general base of an excavation, to collect unwanted water for the purpose of facilitating its removal.


The discharge of water from a surface.

Tensile strength

Maximum amount of pressure a material can be subjected to before breaking.

Thermal expansion/contraction

The expansion and contraction of a material due to changes in its temperature.


The permissible limit of variation in a dimension or parameter of a manufactured object. Dimensions and parameters may vary within certain limits without significantly affecting function. Tolerances are specified to allow leeway for imperfections in manufacturing without compromising performance.

Total coated thickness

The thickness of metal sheeting including the thickness of the coating.

Trimming (trim)

The finish materials in a building, such as mouldings, applied around openings (windows trim, door trim) or at the floor and ceiling of rooms (baseboard, cornice, and other mouldings).

Turn down

Mechanically turning down the pan of a roof sheet into the gutter.

Turn up

Mechanically turning up the pan of a roof sheet under the ridge.


Internal intersection of two roof slopes.


An opening, usually on the roof, which allows the escape of air.

Vent ridge

A vent ridge runs the entire length of the roof peak, blending into the roof line for a more attractive home.

Water carrying capacity

The maximum amount of water that the roof sheeting can carry.

Wind load capacity

The maximum limit a structure can withstand from wind speeds and associated pressures without failure.