Metal Roof Defects

The following guidelines apply to residential cladding. Cosmetic issues are very subjective according to the degree of visibility and the nature of the job, and this should be taken into consideration when assessing compliance.

Scratches

Due to the self-healing qualities of metallic coated profiled roofing and factory applied organic coatings, minor scratches will not affect durability as long as they do not extend to the base metal. Generally, isolated scratches that are not readily visible from a distance of 3 m are deemed acceptable.

Swarf

Visible swarf resulting from the use of incorrect cutting practices, or grinders, is a defect. Light swarf and rust spots arising from recommended cutting and drilling practices should be removed, but harsh abrasion is not recommended, and some light residual staining is not a defect.

Paint Fade and Colour Differentiation

Excessive paint fade from factory finish, or differential fade from different paint systems or suppliers, is not acceptable and is a defect.

Accessories colour matched before installation may fade at a different rate to the cladding, and this is not a defect.

Colour matched paint may be used to pre colour match certain accessories before installation. If used to repair scratch damage to roof or wall cladding it is a defect.

Fastener Pattern

Fasteners should be installed in a regular pattern following the Code of Practice or manufacturer’s literature. Fasteners should be applied to all support members crossed by the cladding, failure to do so is a defect unless specifically allowed by the designer or engineer.

Fastener Alignment

The degree of fastener alignment that is acceptable varies with the visibility and line of sight of the roof. Fasteners on wall cladding, or on highly visible roof sections, not aligned within 10 mm is a defect.

Fastener squareness

Fasteners not driven square to the profile within 5° of vertical is a defect.

Uneven Notching

Notching of flashings over ribs that is not symmetrical and consistent, with gaps greater than 5 mm is a defect.

Oil Canning

Oil canning is common with standing seam products and can occur with other wide pan profiles from time to time. This will become less apparent with weathering and is not a defect with those profiles.

Lichen

Lichen build up is a natural; occurrence and not a defect. However, its presence will affect the durability of the roof and it should be removed as recommended by the manufacturer.

Clip Creasing

For strength of engagement, a secret fix clip into trough section is normally required to have an interference fit, which may show through the narrow throat of the rib. This is will become less apparent with weathering and is not a defect provided deflection is less than 3 mm.

Sunscreen Damage

Improper formulations of sunscreen may affect the paint coating on contact. This is a defect and these sheets should be replaced.

Thermal Noise

Some roof noise must be expected, particularly when translucent sheet is used and is not a defect. Flashings should be designed to minimise thermal and wind noise. Environmental noise is not a defect.

Incompatible materials

Runoff from copper onto painted and unpainted metallic coated profiled metal is unacceptable and is a defect. Contact with copper, lead, stainless steel, cedar, wet concrete wet butyl rubber soil, fertiliser, and certain other materials is a defect. See Compatibility.

Leaks

Leaks are unacceptable, and they are a defect.

Staining

Staining caused by runoff from materials that are incompatible with the roof material is a defect. Examples are copper, concrete splashing, harsh chemicals, and solvents. Solutions range from cleaning to sheet replacement

Condensation

Excessive or persistent condensation and should be discussed with the main contractor or designer. Condensation caused by the drying of wet timber or concrete is not a defect and should be managed by the contractor to minimise the effect.

Squareness of lay

The degree of squareness that does not constitute a defect depends on the application and exposure of the cladding, and the squareness of the structure on which the cladding is being laid. Generally, variation of up to 20 mm in 10 m is not a defect for roofing. Wall cladding should generally be square to within 10 mm in 10 m or 5 mm per 10 m in highly visible situations.

Exposed Sealant

Exposed sealant will attract dust and is a cosmetic defect. If it is in evidence of the sealant being applied on top of the joint rather than sandwiched between the two surfaces, it is a defect.

Strippable Film

Strippable film left exposed to sunlight too long and that cannot be removed without damaging the sheet is a defect.

Rib Dents

Isolated rib dents will become a weatherproofing defect and can be repaired with a rib cap riveted over the affected area. Repaired isolated dents are not necessarily a defect. Sheets having two dents within a purlin space are a structural defect and should be replaced.

Ponding

Complete blockage of the pan by the installation of penetrations is a defect. Flat back flashings that hold more than 3 mm depth of water, or sheet pans that do not drain freely due to insufficient fall or structural damage is a defect.

Back Flashings

Back flashings greater than 1 m in width should be avoided by design and are a defect.

Contamination

See staining, above.

Glare

Glare will reduce with time and is not a defect.

Overhang into gutter

Overhang into the gutter of less than 30 mm is a defect. When the roof sheet ends are not protected by thefront of the spouting, and an eaves flashing is not installed, an overhang of less than 45 mm is a defect.

Bird Entry

Details that allow birds to enter the roof cavity are a defect

Purlin Creasing

Minor creasing when using wide pan trapezoidal profiles, particularly in 0.40mm steel and 0.70mm aluminium is not a defect and can be expected. Major creasing due to purlin misalignment, overtightening of screws or traffic is a defect.

Side Lap Visibility

The side lap of cladding may be uniformly visible from certain angles which is a result of anti-capillary design, and this is not a defect.

Concertina Effect

Crushing of flashings due to shrinkage of timber to which it is attached is a defect.

Spouting, Fascia/Gutter

Strippable film left on fascia gutter is a defect. Film residue should be removed. Joints should be neat and fastenings colour matched and aligned with no visible silicone.

Brackets must fit correctly; bracket marks and rattling are defects. Gutters should fall towards an outlet, ponding of up to 5 mm is not a defect. Internal gutters must be provided with an adequate overflow. Downpipes should be aligned parallel with the most adjacent vertical element.