Asbestos is the generic term for a number of fibrous silicate minerals. Products made from asbestos cement - a bonded asbestos material - include fibro sheeting (flat and profiled) guttering and downpipes, as well as other pipes for water, drainage or flues, corrugated roofing sheets, roofing shingles and guttering.
Asbestos is a type of building material used in the building industry between the 1940s and late 1980s.
Before the health risks were known, asbestos products were widely used because they were durable, fire resistant and had good insulation properties.
The manufacture and use of asbestos products was banned nationally from 31 December 2003. This ban applies to manufacture, supply, storage, sale, use, reuse, installation and replacement of asbestos.
Asbestos has many properties that once made it attractive to industry:
- stability when heated
- strength under tension
- chemical resistance
- water resistance or absorbency (depending on type of asbestos)
- suitability for weaving and reinforcing
- electrical resistance.
Friable vs non-friable asbestos
Asbestos-containing materials fall into two broad categories: friable and non-friable (also known as bonded).
'Friable' is used to refer to asbestos-containing materials that can be easily reduced to powder when crushed by hand, when dry.
These materials can contain high percentages of asbestos fibres and are more likely to release these fibres into the airborne environment when disturbed. As such, they pose a greater risk to health.
Friable materials must only be handled and removed by an asbestos removalist with an 'A' class licence.
Examples of friable asbestos-containing materials include:
- some sprayed on fire retardants
- sound proofing and insulation
- the lining on some old domestic heaters, stoves and hot water systems and associated pipe lagging
- the backing of sheet vinyl and linoleum floor coverings
- thermal lagging, such as pipe insulation.
'Non-friable', or bonded asbestos is used to refer to asbestos-containing materials in which the asbestos is firmly bound in the matrix of the material. These materials are unlikely to release measurable levels of asbestos fibre into the airborne environment if they are left undisturbed. Therefore, they generally pose a lower risk to health.
They are mainly made up of asbestos fibres together with a bonding compound (such as cement), and typically contain up to 15 per cent asbestos.
Non-friable materials containing asbestos are solid, quite rigid and the asbestos fibres are tightly bound in the material. Non-friable materials containing asbestos are the most common in domestic houses. They are commonly called 'fibro', 'asbestos cement' and 'AC sheeting'.
Examples of non-friable asbestos-containing materials include:
- asbestos cement products (flat, profiled and corrugated sheeting used in walls, ceilings and roofs, moulded items such as downpipes)
- plaster patching compounds
- textured paint
- vinyl floor coverings.
Low density asbestos fibre board
Low density asbestos fibre board (LDB) is a lightly compressed board which looks similar to asbestos cement sheeting or plasterboard but is different to asbestos cement (AC) sheeting because it can be easily bent in the hand or dented by soft pressure. It is softer than AC sheeting because calcium silicate plaster was used to bond the material instead of cement.
The asbestos content of lightly compressed board can range up to 70 per cent. It was manufactured as a flat sheet product although some perforated sheeting, typically used for acoustic ceiling applications, was also manufactured.
Commonly known as low density asbestos fibre board, some product names include 'Asbestolux' and 'Duralux'. If LDB is in good condition and left undisturbed it presents a low risk. However, because it is softer than AC sheeting, low density board can crumble more easily when disturbed.
A person conducting a business or undertaking planning to remove LDB will need to determine whether the material is friable or non-friable on a case by case basis. Such assessments may only be undertaken by persons who are competent in working with asbestos-containing materials. Where the assessment indicates the LDB is in poor condition and/or could become friable (e.g. breaking up) during the removal process, a class A asbestos removalist must be engaged to safely remove the material.
Due to the need for professional assessment of the friable nature of LDB as well as its high asbestos content with subsequently higher potential to release asbestos fibres, homeowners must not undertake any work with this product. Homeowners should ensure an appropriately qualified tradesperson is engaged for any work with LDB. The Public Health Act 2005 prohibits the removal of friable asbestos products unless the person holds an A class licence.
The Guide to identifying and handling low density asbestos fibre board (LDB) provides more information about identification of LDB and how to work safely with it.