A range of components used to weatherproof the roof. For example; flashings, ridge cappings and barge cappings.

AHI Roofing

AHI's head office is located in Glen Innes, Auckland, New Zealand. AHI Roofing manufactures and markets Gerard Roofs - the versatile range of steel panels asked for by name and demanded by trade professionals and discerning homeowners around the world.

Barge Board

The timber fixed along the pitched edges of a gable to cover the ends of a roof.

Barrel Cap

A rounded accessory used to flash ridges, hips and barges.


The means of supporting, positioning, or fixing your new roof. Usually made of timber.

Box Barge

A standard metal accessory used to flash gables and barges.


Any additional support required in the structure of roofs, wall frames and so on. Generally timber or steel and diagonally positioned between frames and studs.

CHH Roofing

A member of Carter Holt Harvey's Building Products and Distribution division between September 1985 and April 1998 before being acquired by AHI Roofing Ltd.


The brand for pre-painted long-run coated by BHP NZ Steel. Generic long-run product is called "G2z".


The number of horizontal rows of tiles, shakes or shingles.


Branded roof restoration coating that is supplied through a nationwide network of licensed applicators. Manufactured by AHI Roofing.


A vertical window that protrudes from a sloping roof area.

Dutch Gables

The combination of a hip and a gable.


Usually made of steel or timber and fixed to the rafter ends onto which a gutter system can be attached. Internal fascia means the gutter is between the fascia and the house. External fascia means the fascia is between the gutter and the house.


Strips of flexible waterproof material used as added protection at various junctures on the roof. Gerard Roofs provide a number of quality flashings including side and apron flashings. See technical details for drawings.


A BHP longrun product that is pre-painted and branded as "Colorsteel". Is warranted in "Moderate" or "Severe" environments but not "Very Severe" environments. See BHP NZ Steel for details.


The same product as Zincalume but branded as Galvalume in various parts of the world.


Steel that has been coated solely in zinc.

Gerard Angle Trim

A pentagonal shaped accessory used to flash the ridge, hips and barges

Gerard Box Trim

A rectangular accessory used to flash ridges and hips.

Gerard Certified Roofer

An expert from our nationwide network of independent roofing companies who is certified to supply and install Gerard pressed steel panels.

Gerard Colortile

Sometimes referred to as simply 'Colortile'. The scalloped shapes of this profile give Gerard Colortile the style of a traditional terracotta roof but in a cleaner, uniform, more modern way. Many people choose Colortile to capture the look of heavyweight tile without its disadvantages. The profile is often seen with brick cladding on traditional homes. This roof isn’t limited to that aesthetic though and is equally appropriate above plaster or weatherboards.

Gerard Corona

Sometimes referred to as 'Corona Shake', 'Corona' or 'Shake'. Combining a flat plane with continuous irregular grooves, Gerard Corona has a recurring yet organic pattern that works with many styles of home. Perhaps because of its sheer versatility, Gerard Corona is New Zealand’s most popular steel roof panel. Seen on a wide variety of homes, from the rustic and rural to the urban and urbane, Gerard Corona is almost the ubiquitous pressed steel roof.

Gerard Oberon

Sometimes referred to as 'Oberon' or 'Oberon Shingle'. The Gerard Oberon profile has a unique depth. Its look changes with the angle of the sun and the intensity of light giving your roof a profound  sense of solidity. A Gerard Oberon roof has a look that echoes an awareness of the grand homes of yesteryear. These roofs are often seen alongside dressed stone and natural timbers on properties of substance and homes on larger sections.

Gerard Roofs

An extensive range of roof styles, colours and finishes manufactured by AHI Roofing Limited.

Gerard Senator

Sometimes referred to as 'Senator' or 'Senator Shingle'. Gerard Senator is a profile with a modern look and subtle raised detailing. Senator is known for the simplicity and uniformity it brings to a roof. This roof embodies an understated quality that works with both contemporary and traditional architecture. The Gerard Senator profile has a distinctive vertical-ridge textured finish that adds refinement and helps give the roof a timeless character.


Small hip to valley areas under 900mm wide.


Classified as any roofing material weighing more than 16 kilograms per square metre of roof area when installed. Can require additional structural support.


Sloping junction of two roofing surfaces that generally meet at an external corner.

Horizontally Fastened

Where roofing products are fitted to the roof structure by means of horizontally fixed fasteners through the nose of a pressed steel panel. A much stronger method of fixing.

Jerkinghead or Hipped Gable

Primarily an overly high gable roof that incorporates hips to visually reduce the effect.

Klass Fascia

Steel rainwater system manufactured by AHI Roofing using G2z pre-painted steel.


Classified as any roofing material weighing less than 16 kilograms per square metre of roof area when installed.


Load-bearing supports over large cavities in wall frame structures such as windows, doors and garage entrances.

Made To Order

Colours that are not held in stock but made to order periodically as demand dictates.

Mansard Roof

A roof on which each face has two slopes, the lower one being steeper than the higher.


A condition that can occur when pre-painted steel is rollformed. The paint surface is stretched along with the steel potentially causing very fine cracks to appear in the surface coating.

OSH - Occupational Safety and Health

This organisation sets guidelines for all health and safety issues relating to all New Zealand workplaces.


The angle or slope of the roof surface.

Pop Top

Where a second storey protrudes from the main roof.

Pressed Steel Tiles

‘Pressed steel tiles’, more correctly referred to as ‘pressed steel panels’, are the fundamental components of the Gerard roofing system. The panels are fixed in horizontal courses, on top of battens attached to the roof rafters, and combine with trims, flashings and other componentry to become a complete Gerard pressed steel roof. 


Usually indicates the shape or design of a roofing product.


Roof frame timbers which support the roofing material.


The process of applying a new surface to an existing roof. This can be done on steel as well as concrete.


The process of replacing an existing roof with a new roof. This can be done by overlaying the new over the old or by completely removing the existing roof before installing the new one.


The topmost horizontal juncture of a roof where two opposite areas of roof rise to meet. 

Ridge Board

Timber supports that ridge flashings are fixed to.


Solid timber sheathing fixed to the rafters. The roofing material is then fixed to the sarking.


A super-tough acrylic surface coating that is baked on aluminium-zinc coated steel panels resulting in a 45 micron coating that resists fading and discolouration. Sometimes referred to as "paint", it is in fact a superior coating applied at high temperatures in a higher quality process than the paint coatings on long-run steel.


A type of roof profile that has the random appearance of warped cedar tiles. May be wooden or steel.


A type of roof profile that has a uniform square appearance. Originally imitated cedar shakes but now a product in its own right. Made out of asphalt or steel with a textured coating.

Skillion or 'Lean-To' Roof

A one-sided pitched roof.


The lined overhang from the outside of the house structure to the edge of the roof.

Tasman Building Products

A group of five established manufacturing and marketing companies supplying quality building products to a host of countries worldwide.


A textured surface gives tiles a softer profile and additional protection. It is achieved by polymer bonding natural stone into an acrylic surface coating. It used to be known as "chip" coating but is in fact a different formula from the old chip coated tiles of many years ago.


Support beams that form the structure of a roof.

Tuffcoat Tile

Sometimes referred to as 'Tuffcoat'. Gerard Tuffcoat is a geometric profile whose shapes and angles accentuate light and shadow to emphasise its corrugations and create a sense of strength and gravity. Often used on homes displaying clear, straight lines in keeping with a bolder, stronger-looking roof, Gerard Tuffcoat is appropriate on architecture where the designer seeks the definition to make the roof a feature in its own right.


A moisture-resistant building paper that is laid over the rafters and under the battens. Required under New Zealand building code 3604 for lightweight roofing as a condensation barrier.


The internal angle formed by the meeting of two roof surfaces. A metal tray is installed in this area to direct water to the gutter.

Vertically Fastened

Where roofing products are fitted to the roof structure by means of vertically fixed fasteners through the top of the product. Can lead to problems if wind uplift is strong.


Commonly found on timber shakes and asphalt shingles where ageing causes the product to bend.


Registered trademark of BHP. A steel base that is coated with a combination of zinc and aluminium. Nowadays most steel roofing materials are manufactured from this.