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

AHI Roofing

The largest steel tile manufacturer in the world. AHI Roofing Limited is wholly owned by Fletcher Building. AHI's head office is located in Glen Innes, Auckland, New Zealand. AHI Roofing manufactures and markets Gerard Roofs - the versatile range of steel tiles 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 longrun coated by BHP NZ Steel. Generic longrun product is called "G2z".


A particular "scalloped" profile in the Gerard range made from steel and coated with special paint or textured coatings. Developed by Gerard Roofs in the late-eighties, the name is sometimes inaccurately used as a generic description for steel tiles. Although copies of this system exist they do not have the same warranties, support or service as the original Gerard Colortile.

Corona Shake

A particular random profile in the Gerard range made from steel and coated with special satin or textured coatings. Developed by Gerard Roofs for the American market in the early-nineties, it has now taken the New Zealand market by storm.


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 in 100 per cent 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 are certified to supply and install Gerard pressed steel tiles.

Gerard Roofs

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


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 (ie through the nose of a metal tile). 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.

Oberon Shingle

A 320mm wide shingle tile with a deeper profile than the Senator Shingle. Developed by Gerard Roofs in the mid-nineties and made from steel with a textured coating, it is the highest quality shingle on the New Zealand market.

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

Steel that has been pressed into the shape of tiles, shakes or shingles. The tiles can be pre-painted or coated after pressing.


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 / flashing is 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 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 longrun steel.

Senator Shingle

A 370mm wide shingle tile with a shallower profile than the Oberon Shingle. Developed by Gerard Roofs in the late-nineties and made from steel with a textured coating. It is second only to Oberon tiles in quality but costs much less.


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-Too 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

Gerard Tuffcoat adds character and strength to a roof and is available in a range of classic and contemporary roof colours in either a satin or a textured finish.


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 (ie through the top of 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.

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