Durability means the capability of a building or its parts to perform a function over a specified period of time. It is not an inherent property of a material or component. It is the outcome of complex interactions among a number of factors, including.
- The service conditions.
- Material characteristics.
- Design and detailing.
(‘ABCB Guideline Document – Durability in buildings: 2003’)
The following sub-sections of the durability topic are written in order to provide general guidelines in how best to provide, enhance and maintain adequate durability of Hebel PowerWall.
6.2 Maintenance and Enhancement of Durability
The durability of Hebel PowerWall can be enhanced by periodic inspection and maintenance. Inspections should include examination of the coatings, flashings and sealants. Paint finishes must be maintained in accordance with the manufacturer’s recommendations. Any cracked and damaged finish or sealants, which would allow water ingress, must be repaired immediately by recoating or resealing the effected area. Any damaged flashings or PowerPanels must be replaced as for new work.
The durability of the system can also be increased by using Class 4 fixings throughout, additional treatment of steelwork, and by painting all exposed sealants to the sealant manufacturer’s recommendations.
6.3 Coastal Areas
Hebel PowerWall can be used in coastal areas with additional precautions to ensure salt does not build up on the surface of the wall. For buildings, which are 200m to 1000m from a shoreline or large expanse of salt water, such as, Swan River (west of the Narrows Bridge), Sydney Harbour (east of the Harbour Bridge or Spit Bridge), one of the following is required:
- All horizontal and vertical movement joints must be appropriately caulked; or
- All walls must be sufficiently exposed from above so that rain can perform natural wash-down of the wall; or
- Walls, which are protected by soffits above, must be washed down twice per year, to remove salt and debris build-up, particularly at the joints.
- In all cases, Class 4 screws must be used.
- For buildings less than 200m from the shoreline as defined above, CSR Hebel does not recommend that Hebel PowerWall be used without project specific consultation with CSR Hebel Engineering Services.
6.4 Hebel PowerPanel
Hebel PowerPanel has many characteristics which make it a very durable product, including:
- Will not rot or burn.
- Is not a food source for termites.
- Unaffected by sunlight.
- Not adversely affected over normal temperature ranges.
- One quarter the weight of conventional concrete.
- Solid and strong with corrosion protection coated steel reinforcement.
6.5 Durability of Components
It is the responsibility of the building designer to ensure that the components, such as screws, top hat battens and other steel components, have the appropriate corrosion protection to be able to maintain their strength and integrity to suit the required design life of the project.
The top hat section specified in this guide can ONLY be used on untreated and dry timber frames. CCA treated pine or green timber frames have a deleterious effect on the top hat coatings, which can lead to corrosion. Where timber is CCA treated, provide a barrier between top hat and timber member. Refer to screw manufacturer for appropriate screw specification for this application.
When assessing durability the following documents can be referred to for guidance:
- ABCB Guideline Document – Durability in buildings: 2003.
- AS/NZS 2312: 2002 – Guide to the protection of structural steel against atmospheric corrosion by the use of protective coatings.
- ISO 9223: 1992 – Corrosion of metals and alloys – Corrosivity of atmospheres -Classification.
- AS3566: 2002 – Self drilling screws for the building and construction industries.
- AS2331 Series.
Reference to AS3566 should always be adhered to when selecting the screws corrosion resistance classification.
6.6 Wall Frames
6.6.1 Steel Frames
The designer needs to ensure that the steelwork and Hebel AAC products have adequate protective systems to ensure that durability is maintained. The durability of the stud frame can be enhanced by the provision of a membrane, such as sarking. The manufacturer of the steel stud frame can provide guidance on the appropriateness of this solution on a project-by-project basis.
The steel frame requirements outlined in the BCA Vol. 2, Part 3.4.2 should be considered in conjunction with steel frame design and construction advice from the steel frame manufacturer. These requirements consist of minimum protective surface coatings with restrictions on the location of the building and exposure condition of the steel frame.
6.6.2 Timber Frames
Information on the durability design of timber structures and components can be obtained from documents such as:
- AS 1720.1 Timber Structures, Part 1: Design Methods.
- AS 1684 Timber Framing Code.
- State timber framing manuals.
- AS 4100 Metal Connectors: Corrosion.
- AS 3600 Subterranean Termites.
Fig. 6.1 Hebel Home