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6.0 Durability PowerWall

6.1 Overview

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.
  • Workmanship.
  • Maintenance.

(‘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

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8.0 Energy Efficiency PowerWall

8.1 Building Code of Australia (BCA)

The BCA is available in two volumes which align with two groups of ‘Class of Building’:

Volume 1 – Class 2 to Class 9 Buildings; and
Volume 2 – Class 1 & Class 10 Buildings – Housing Provisions.

Each volume presents the Performance Requirements for the efficient use of energy for internal heating and cooling in buildings. The majority of changes have been associated with the Housing Provisions.

The Performance Requirements for energy efficiency ratings are dependent upon the form of construction (i.e. walls or floors), Class of Building, and the type of areas being separated. The performance requirement is a value that is the Total R-Value, which is the cumulative total of the individual R-Values of the building system components.

8.2 Hebel PowerWall

One of the primary design objectives in planning a building is to provide a cost effective comfortable living/ working environment for the building’s inhabitants. Exploiting the inherent thermal mass and insulation qualities of Hebel enables the designer to achieve this objective.

Several international comparative studies have been conducted to investigate the benefits of incorporating AAC walls in place of conventional wall systems.

A common trend was the lower heating and cooling energy consumption and smaller mechanical equipment required to maintain a comfortable living environment, especially with regards to regions of mainly cold weather. The excellent performance was the result of the three characteristics – thermal mass, thermal insulation, and the air tightness of the construction.

The level of insulation provided in a wall is determined by the required Total R-Value. The higher the required Total R-Value the greater the insulation provided. Hebel PowerWall incorporating CSR Bradford insulation can provide the R-Value ratings outlined in Table 8.1.

8.3 Thermal Insulation

It is recommended that insulation materials be installed to enhance thermal insulation properties and occupant comfort. Insulation also improves the acoustic performance of the wall against outside noise.

The BCA provides Deemed-to-Satisfy Provisions for compliance and installation of the various types of insulation. The insulation should be installed in Hebel PowerWall such that it forms a continuous barrier to contribute to the thermal barrier. All insulation installed in Hebel PowerWall must comply with: AS/NZS4859.1; or AS2464.3 for loose fill insulation.

8.4 Air Tightness

As outlined in Section 8.1 the thermal performance can be influenced by many factors. Most of these are related to the design decisions and properties of the adopted materials. Construction practices can also significantly affect the performance with poor sealing, resulting in drafts. The tight construction tolerances of AAC provide a wall with low air infiltration rate. Testing at the CSIRO (Test Report DTM327) on Hebel blockwork with thin bed adhesive joints has determined an air infiltration rate of 0.3L/s (0.014% of internal volume). For PowerPanels having fewer thin bed adhesive joints, a rate less than this could be achieved.

8.5 Sarking

As well as controlling condensation and acting as an air barrier, a sarking can be used to significantly improve the thermal insulation and energy efficiency performance of a building solution. Sarking layers can alter the performance of the cavity by providing a reflection side. The design of the sarking arrangement is complex and should be performed by the appropriate project consultant.

Where the sarking layer provides a weatherproofing function, the sarking material must comply with AS/NZS4200 Parts 1 and 2.

Where sarking is installed in the PowerWall, panels must be fixed from the outside.

Table 8.1 Energy Efficiency

The following tables show the performance levels required for walls and floors under the BCA and the thermal performance of the Hebel PowerWall system.

Climate Zones 1 2 3 4 5 6 7 8
 Multi-Residential Class 2, 3, 4 & 9c buildings
Minimum required R-Value for walls R1.4 R1.4 R1.4 R1.7 R1.4 R1.7 R1.9 R2.8
Minimum added R-Value of insulation 0.49 0.49 0.49 0.79 0.49 0.79 0.99 1.89
Minimum complying PowerWall system 102 102 102 103 102 103 103 105
Detached Houses Class 1 & 10a buildings
Minimum required R-Value for walls R1.9 R1.9 R1.9 R2.2 R1.9 R2.2 R2.4 R3.3
Minimum added R-Value of insulation 0.99 0.99 0.99 1.29 0.99 1.29 1.49 2.39
Minimum complying PowerWall system 103 103 103 104 103 104 104 105

• Refer to BCA for state & territory variations.
• Refer to BCA for alternative means of satisfying the required performance levels.
• Refer to CSR Bradford product literature for design & installation requirements for the nominated reflective foil laminates and insulation.

Energy Rating Software
Energy legislation (5 stars) is changing every year and ratings software is changing to keep up. Combine this with all the variable elements in a house such as window sizes, floor space and house orientation and you have a moving landscape. Hebel provides a great springboard for walls and floors in these rating systems due to its unique thermal properties of insulation AND mass. When rating in FirstRate, AccuRate, BASIX and BERS select AAC as the wall and floor option and see why Hebel is fast becoming the all star performer. Hebel can help your project achieve 5 stars and beyond.


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2.0 Benefits PartyWall

The many benefits of using Hebel PartyWall in low rise multi-residential construction include:

  • Acoustic Performance: Significantly reduced sound transmission between units and rooms.
  • Good Impact Noise Resistance: 75mm Hebel Intertenancy 001 has discontinuous construction and can be selected to reduce the transfer of impact noise.
  • Fire Protection: Tested systems have very good fire rating properties.
  • Lightweight: Lighter loads on structures compared to masonry block, for equivalent Rw + Ctr rating.
  • Slender Walls: Wall thicknesses range from 275 to 325mm.
  • Cost Effective: Cost savings compared to traditional masonry construction.
  • No Wet Trades: Less mess and a cleaner, safer work area.
  • Less Wastage: Greatly reduced waste, as panels are available in a range of standard lengths. This allows for bestsuited panel length selection, which eliminates or reduces off-cut waste.
  • Speed of Construction: Fast installation and assembly speeds with smaller construction crew requirements.
  • Security: Steel reinforced AAC panels provide a high degree of security between units.
  • Thermal Resistance: Excellent thermal resistance.
  • Technical Support: Competent technical staff can assist with systems information.

The following images show a typical two storey Hebel Party Wall installation.

 Image 2.1: PowerPanel installed in ground floor PartyWall.

 Image 2.2:  Awaiting installation of base track and panels for second storey.

Image 2.3: Second storey panel installation.

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6.0 Design Approach PowerBlock

There are 2 methods of constructiontypical and tie-down. Typical is the most common method of building whilst the tie-down method is required for cyclonic or high wind areas (as determined by an engineer). This guide provides information for both building methods.

Important Note

It is the responsibility of the architectural designer and engineering parties to ensure that the information in the Hebel PowerBlocks Design and Installation Guide is appropriate for the intended application. The recommendations of this guide are formulated along the lines of good building practice, but are not intended to be an exhaustive statement of all relevant data. Hebel accepts no responsibility for or in connection with the quality of the recommendations or their suitability for any purpose when installed.


The Hebel PowerBlocks Design and Installation Guide has been created to provide information for detached residential buildings. The design information in this guide has been condensed from the Hebel Technical Manual and AS3700 Masonry structures. The design basis is AS3700 Masonry structures, Section 12 Simplified design of masonry for small buildings. The footing and slab design is based on AS2870 Residential slabs and footings – Construction.

Refer to Table 6.1 for Building Geometry Limitations.

Design Parameters

The structural design information in this guide is based on the data and assumptions in Table 6.2, 6.3 and 6.4.

Design Sequence

Fig. 6.1 details Hebel recommendations for how to design a Hebel PowerBlock home.

Fig 6.1:  Flow Chart

Table 6.1: Buiding Geometry Limitations
2 storeys max
 Max. height to underside of eaves  6.0m
 Max. height to top of roof ridge  8.5m
 Max. building width incl. verandah but not eaves  16.0m
 Max. building length  5x width
 Max. lower storey wall height  3.0m
 Max. upper storey wall height  2.7m
 Max. floor load width on external wall  3.0m (6.0m single span floor)
 Max. floor load width on external wall  3.0m (6.0m rafter/truss span)
 Max. floor load width on internal wall  6.0m

Where the building geometry is outside the above limitations, the designer must refer to the Hebel Technical Manual and AS3700 Sections 1-11.

Table 6.2: Design Parameters
Hebel PowerBlock material properties:
 Nominal Dry Density  470 kg/m2
 Working Density (S.T.)  611 kg/m2
 Working Density (L.T.)  500 kg/2
 Characteristic Compressive Strength, f’m  2.25 MPa
 Characteristic Flexural Tensile Strength, f’mt  0.20 MPa
Characteristic Shear Strength, f’ms  0.30 MPa
Characteristic Modulus of Elasticity, EST  1125 MPa
Characteristic Modulus of Elasticity, ELT  562 MPa
Table 6.3 Design Parameters – Permanent and Imposed Actions
Permanent Actions (Dead Loads):
 Floor – Superimposed  1.00 kPa
 Roof – Tile  0.90 kPa
 Roof – Sheet  0.40 kPa
 Framed Floor/Deck – Timber  0.50 kPa
 Framed Deck – Tile  0.50 kPa
 Pergola Roof – Tile  0.80 kPa
 Pergola Roof – Sheet  0.32 kPa
 Hebel PowerFloor System  0.80 kPa
 Hebel Floor Panel System – 250mm  1.90 kPa
 Hebel PowerBlock Wall – 250mm, 2700mm (H)  4.60 kN/m
 Hebel PowerBlock Wall – 150mm, 2700mm (H)  2.76 kN/m
Imposed Actions (Live Loads):
In accordance with AS 1170. 1:2002
 Floor – general  1.50 kPa
 Deck  2.00 kPa

Image 6.1:  Hebel PowerBlock home


 Image 6.2:  Hebel PowerBlock home

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Construction Details – Tie-down PowerBlock

Required only if specified by design /project engineer

Fig 15.1:  Strip Footing, Double Brick Sub-Floor

Fig 15.2:  Strip Footing, Concrete PowerBlock Sub-Floor

Tie down rods/engineering restraints must be embedded into the footing and pass up through the sub floor and into the Hebel PowerBlock work.

Table 15.1 Top-Plate & Hold-Down selection



Top Plate & Hold-Down

Tile Roof

Sheet Roof

N1 A / B / C B / C
N2 A / B / C D / F
N3 D / F D / F
N4 D / F D / F
N5 E / G E / G
N6 E / G E / G
C1 D / F D / F
C2 E / G E / G
C3 E / G E / G
C4 G G


A 90×45 F7 timber top plate / 700mm deep strap @ 1200mm ctrs.
B 90×45 F17 timber top plate / 1700mm deep strap @ 2400mm ctrs.
C 90×45 F17 timber top plate / Ф12mm rod @ 2400mm ctrs.
D 90×45 F17 timber top plate / Ф12mm rod @ 1200mm ctrs.
E 90×45 F17 timber top plate / Ф12mm rod @ 900mm ctrs.
F 100x50x3.0 RHS top plate / Ф12mm rod @ 2400mm ctrs.
G 100x50x3.0 RHS top plate / Ф12mm rod @ 1200mm ctrs.

Fig 15.3 Hold Down Detail for Reinforced Bracing Walls

Table 15.2 provides ultimate racking capacities of reinforced 150mm and 250mm Hebel PowerBlock walls. The reinforcement is N12 bar or 12mm threaded rod at nominal 1000mm centres. The reinforcement must be tied to the footings and wall top plate through the bond beam.

Walls resisting racking forces should be evenly distributed within a house and spaced at a maximum of 8.0m. Ceiling and floor diaphragms must be adequately tied to walls to ensure transfer of forces through to the footings.

For more information about bracing, refer to Section 6.11 of the Hebel Technical Manual.

Fig 15.4 Roof Top to Plate Fixing to Hebel Wall – Strap (elevation)

Top Plate Hold-Down

Two tie-down methods are provided in this design guide.

  1. Strap – 30×0.8mm cut into inside face of external wall min. 700mm deep.
  2. 12mm threaded rod continuous from footing through bond beam to top plate.

Fig 15.5 Roof Top Plate Fixing to Hebel Wall-Tie-Down Rod (elevation)

Three top plates options are provided in this design guide:

  1. 90×45 F7 timber
  2. 90×45 F17 timber
  3. 100x50x3.0 RHS

The type of hold-down method and spacing depends on the top plate, roof type/span, and wind classification. Refer to Table 15.1 for specifications. For high wind areas, the bracing design is likely to require tie-down rods which will drive that as the hold-down method.

Table  15.2 Reinforced Wall – N12 Bars at Nom. 1000mm CTRS

Min. No. of
N12 Bars
Ultimate Racking Capacity (kN)
150mm PowerBlock 250mm PowerBlock
 900  2  5  6
 1200  2  8  8
 1800  3  16  18
 2400  3  24  25
 3000  4  36  38
 3600  5  45  46
 4800  6  54  56
 6000  7  63  66

 Base of Wall

Fig 15.6 Hebel PowerBlock work on Stiffened Raft Slab Edge Foundation (elevation)

Fig 15.7  Concrete PowerBlock Sub-Floor Detail (elevation)

 Fig 15.8  Double Brick Sub-Floor Detail (elevation)

Fig 15.9 Ring Beam Internal Non-Loadbearing Wall (elevation) (No tie down – as specified by design engineer)

Top of Wall

Fig 15.10 Roof Top Plate Fixing to Hebel Wall – Tie-Down Rod (elevation)

Fig 15.11 Internal Hebel Load Bearing Wall and Timber Floor Frame Junction (elevation)

Wall Junctions

Fig 15.12 External Wall and Internal Partition Wall Junction (plan)

Fig 15.13  External Corner with Control Joint (plan)

Control Joints

Fig 15.14 Control Joint detail (elevation)

Fig 15.15 Typical Bond Beam Control Joint – elevation (Location where no tie down required – as specified by engineer)

Fig 15.16 Typical Ring Beam Control Joint – elevation (Location where no tie down equired – as specified by engineer)

Fig 15.17 Typical Control Joint – plan 

Fig 15.18 Hebel PowerBlock work Typical Movement Joint Detail (elevation)

Fig 15.19 Hebel PowerBlock work Typical Movement Joint Detail (plan)

Fig 15.20 Built-in Column Detail (plan)

Fig 15.21 Built-in Column Detail (elevation)

For all other design details (eg. door, window, floor panels) please follow the previous construction details in Section 14.0)

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