Decramastic Roofs in Australia: History, Materials, Maintenance and Replacement
Decramastic roofing is a distinctive Australian roofing material that can still be found on older homes across Australia. From the street, a Decramastic roof can look much like a conventional tiled roof, but the construction is quite different. Instead of individual concrete or terracotta tiles, Decramastic roofing was manufactured as lightweight, pressed metal sheets formed to imitate the appearance of roof tiles.
The product became popular in Australia during the 1970s, particularly on residential properties and some public and government buildings. Today, many of these roofs are approaching, or have exceeded, 50 years of service and are increasingly being considered for roof restoration or complete replacement.
For homeowners, roof inspectors and roofing contractors, understanding what Decramastic roofing is—and particularly the potential asbestos issue associated with older products—is important before any maintenance or roofing work begins.
What Is a Decramastic Roof?
Decramastic was a pressed metal imitation-tile roofing product. Australian asbestos safety information describes Decramastic as shaped metal sheets manufactured to resemble individual roof tiles. The sheets were approximately 1,350 mm by 400 mm and were also marketed under the name Decrabond. A similar product known as Harveytile was also sold in Australia.
The appearance was quite different from conventional corrugated metal roofing. Rather than presenting as long continuous sheets, the pressed profile created the visual effect of rows of individual tiles.
This gave homeowners the appearance of a tiled roof while retaining some of the advantages associated with lightweight sheet roofing.
The product was originally developed in New Zealand by AHI Roofing in 1957 and subsequently became popular in Australia. By the mid-1970s, Decramastic had become an established roofing material in the Australian housing market. In 1977, ACI Decramastic stated that approximately 30,000 Australian homes had the product installed.
What Was Decramastic Roofing Made From?
One point that can cause confusion today is the material used to manufacture Decramastic roofing.
Australian government asbestos information describes the product as a pressed aluminium sheet with a grit-like matrix attached using an asbestos-containing bituminous product.
Other Australian asbestos-product records describe Decramastic as shaped steel sheet with a bituminous coating and stone or pebble chips added to produce the appearance of cement tiles.
This reflects the fact that different products, versions and descriptions existed over the product’s history. Consequently, it is not appropriate to assume that every imitation-tile metal roof found on an Australian home is identical simply because it looks like Decramastic.
The stone or pebble finish was an important part of the product. It helped produce the textured appearance associated with conventional tiled roofing and was available in a range of colours.
Why Was Decramastic Popular in Australia?
During the 1970s, Decramastic offered an alternative to traditional concrete and terracotta roof tiles.
A major attraction was its relatively lightweight construction. Traditional tiled roofs require a substantial roof structure to support the weight of the tiles, whereas lightweight metal roofing can provide a different structural loading arrangement.
Decramastic was also promoted as a cost-effective roofing option and was used for both complete roofs and building extensions. Australian historical records describe it as being marketed as a cheaper alternative to older cast iron and asbestos roofing products.
The tile appearance was another advantage.
For homeowners who wanted a traditional tiled appearance without installing thousands of individual tiles, the pressed-metal format provided a different approach to roof construction.
Decramastic, Decrabond and Harveytile
Several names can be encountered when researching older Australian imitation-tile roofs.
Decramastic is the name most commonly associated with the product. Decrabond was another name used for Decramastic products, while Harveytile was a similar imitation-tile roofing product that was also sold and installed in Australia.
This is important when researching an older roof because homeowners, building inspectors and roofing contractors may use the terms interchangeably even though the exact product and construction may differ.
The appearance alone should therefore not be relied upon to identify the precise material.
The Asbestos Issue With Older Decramastic Roofs
The most important issue when dealing with an older Decramastic roof is the possibility of asbestos-containing material (ACM).
Some older Decramastic products used a bituminous coating containing asbestos. Australian government information records Decramastic and similar imitation-tile products as having been produced and used from the 1950s through to the early 1980s, with asbestos-containing versions being particularly relevant to older installations.
The asbestos-containing coating was used beneath the stone or grit finish.
Importantly, not every Decramastic roof should automatically be assumed to contain asbestos, particularly because similar non-asbestos products were marketed from the early 1980s onwards.
However, the age of many Australian Decramastic roofs means asbestos should be considered whenever an older roof is being inspected, repaired, cleaned or replaced.
Australian guidance states that asbestos cannot reliably be identified simply by looking at a building material. Where identification is necessary, sampling and laboratory analysis should be undertaken by appropriately competent people, with testing performed by a NATA-accredited laboratory or other laboratory permitted by the relevant regulator.
What Happens to an Older Decramastic Roof?
After several decades of exposure to Australia’s weather, an older Decramastic roof may show significant deterioration.
Common signs can include:
- Loss of the original stone or grit coating
- Surface corrosion
- Rusting around fixings
- Loose or damaged sheets
- Deteriorated ridge and hip areas
- Failed sealants
- Deteriorated flashing
- Blocked or damaged gutters
- Water entry around roof penetrations
- Deterioration caused by repeated repairs
- Discolouration, moss or lichen growth
- Deterioration of the original coating
The condition of the roof should be assessed as a complete roofing system rather than simply judging the visible condition of the metal sheets.
Ridge capping, valleys, flashings, penetrations, gutters, downpipes and roof fixings can all contribute to the performance of the roof.
Can a Decramastic Roof Be Restored?
Whether an older Decramastic roof can be restored depends on its condition, the particular product and whether asbestos is present.
A roof with sound sheets, adequate fixings and limited corrosion may be capable of refurbishment. However, extensive corrosion, widespread coating failure, repeated patching, damaged sheets or deterioration around the roof structure can make complete replacement a more practical option.
Where asbestos-containing material is suspected, ordinary roofing maintenance should not proceed until the asbestos issue has been properly considered.
The condition of the coating is particularly important. Australian asbestos guidance notes that the adhesion of the coating on affected imitation-tile products can deteriorate with age and that asbestos-containing debris may accumulate in roof gutters.
Replacing an Old Decramastic Roof
For a severely deteriorated Decramastic roof, replacement may involve removing the existing roofing and installing a modern Australian roofing material.
Depending on the house design, roof structure, location and owner’s requirements, replacement options may include:
- Concrete roof tiles
- Terracotta roof tiles
- Modern metal roofing
- Other approved lightweight roofing systems
The choice should be based on the existing roof structure, roof pitch, drainage requirements, wind conditions, appearance, budget and applicable Australian building requirements.
If asbestos is suspected, removal must be planned around the requirements that apply in the particular Australian state or territory.
Safe Work Australia notes that asbestos may still be present in older buildings, including roofs, gutters and other building products, despite the national prohibition on asbestos use.
Decramastic Roofs: What Australian Homeowners Should Know
Decramastic roofing is an important part of Australia’s residential roofing history. It provided homeowners with a lightweight alternative to traditional tiled roofing while retaining the appearance of individual roof tiles.
However, the age of many remaining Decramastic roofs means that deterioration and asbestos considerations should be taken seriously.
If you own or are considering purchasing a property with an older imitation-tile metal roof, identifying the roofing material should be one of the first steps before arranging cleaning, repairs, restoration or replacement.
Do not assume that an old Decramastic roof is asbestos-free simply because it looks like metal. Equally, do not assume that every Decramastic-style roof contains asbestos. The age, product type and, where necessary, appropriate testing need to be considered.
For older Australian homes, a professional roof inspection can help determine the condition of the roof covering, ridge capping, flashings, valleys, gutters and associated components and identify whether further investigation of suspected asbestos-containing material is required.
The national asbestos ban prevents asbestos from being manufactured, imported, supplied, sold or installed in Australia today, but it does not remove asbestos-containing products that were already installed in older Australian buildings.
For homeowners, the key message is simple: if an older Decramastic roof needs work, identify the product first, assess its condition, and deal with any potential asbestos before disturbing the roof.
Information about asbestos requirements can vary between Australian states and territories. Homeowners should check the requirements applying in their location and use appropriately qualified and licensed professionals where required.