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									                                    CSR Hebel Block Design & Construction
6.0 CSR Hebel Block Design & Construction

6.1 Residential Footing System –                          Step Two: Assess the Topography
    Designs for CSR Hebel Blockwork                       Typical topographical items that should be
The selection of the foundation type for use with         considered as a site inspection are:
CSR Hebel blockwork is based on AS2870-1996,              a. Is the site level or sloping? If any part of the
“Residential Slabs and Footings”.                            foundation is on fill more than 50mm deep it is
This standard covers the selection of footing designs        classified as sloping.
for the usual range of site conditions, i.e. soil types   b. What will be the maximum depth of cut? A
and slopes. Where unusual site or load conditions            retaining wall will be required for cuts deeper
are considered, advice should be obtained from a             than 600mm within 2m of the building.
practicing Structural Engineer.
                                                          c. Can surface water be diverted away from the
The recommended approach in foundation design                building? Surface gutters and/or agricultural
is to first classify the foundation soil, then assess        pipes may be required.
the topography and select the appropriate footing
design to be used.                                        d. Will it be necessary to fill any part of the site
                                                             to provide support for the foundations?
Step One: Classify the Foundation Soil                       Fill must be suitably compacted in layers.
The foundation soil provides support for the                 Fill containing clay will cause many problems.
building. If there is reactive clay in the soil it may       It is preferable to import sandy fill.
swell on wetting and shrink on drying, causing
                                                          e. Will fill require retaining? Soil filling can be
foundation movement to an extent that may cause
                                                             compacted to a slope not steeper than 1:2 without
cracking of the walls.
                                                             the need for a retaining wall.
The appropriate soil classification for a particular
                                                          Note that for sloping sites it may be necessary
site may be obtained from the following sources:
                                                          to retain fill under the slab by using deep edge
a. Advice from a Geotechnical Engineer.                   beams.
b. Local Council or other local authority for their       Step Three: Select the Footing Type
   information on the locality.                           It is recommended that all walls constructed using
c. A local Builder or Engineer familiar with the          CSR Hebel blocks are classified as full masonry.
   site classification.                                   However, unlike clay brick walls, the integrity of
                                                          a Hebel wall is more critical because of the ‘flush
                                                          type’ finish of the coatings used. This requires a
                                                          stiff footing system when used as either a masonry
                                                          or veneer or a single skin. Unless articulated, all
                                                          walls built in CSR Hebel should be classified as
                                                          full masonry for the purposed of footing selection.

6              CSR Hebel Block Design & Construction

    The wall classification may be changed to               A slip join/bond breaker (DPC) must be installed
    articulated full masonry where movement joints          between the first course and the footing or slab on
    have been used in the external walls at no more than    all internal and external walls to allow for
    6m spacing and internal walls are articulated in        differential movement between the blocks and the
    accordance with the code. AS3700-1998 Masonry           support structure. Refer to Detail F1 to F4 on pages
    Code recommends all internal openings to be full        6.75-6.78.
                                                            Walls supporting suspended concrete floors require
    Example 1                                               a suitable slip joint at the interface such as, two
    For a single skin non-articulated CSR Hebel             layers of greased, galvanised iron. Refer to Detail
    building on class M soil, using a stiffened raft on a   FL3 on page 7.12.
    level site:                                             6.3 Lateral Stability of Hebel Walls
    Depth of edge and internal beams:           800mm
                                                            Free standing Hebel walls which have no returns
    Max. spacing of internal beams:                 4m      or anchorage to a base should not be used in any
    Reinforcing in beam:                         3-Y16      circumstances.
    Slab fabric:                                  RF92      All temporarily free standing walls shall be braced
    Example 2                                               during construction, in accordance with relevant
                                                            standards or project engineer’s instruction.
    For a single skin articulated CSR Hebel building
    on a class M soil, using a stiffened raft on a level    Hebel walls with returns should be checked for
    site:                                                   lateral stability. As a rough guide, if a return on a
                                                            wall is less than 400mm then that end of the wall
    Depth of edge and internal beams:           500mm
                                                            is without adequate lateral support and requires
    Max. spacing of internal beams:                 4m
                                                            fixing to a support or bracing.
    Reinforcing in beam:                       3-12TM
                                                            In some buildings where window openings go all
    Slab fabric:                                  RF82
                                                            the way to ceiling height the intermediate wall may
    It is recommended that a practicing Structural          be free standing. These blades should be carefully
    Engineer is consulted concerning the application        checked and braced during construction. Likewise,
    of AS 2870 to any particular building construction      monolithic Hebel columns can be used, but should
    or site.                                                be designed in accordance with AS 3700-1998.

    6.2 Use of Damp-proof Course and                        Intermediate Hebel columns in double garages
        Slip Joints                                         should be a minimum of 400mm x 300mm to
                                                            provide adequate seating for lintel beams. It is also
    A damp-proof course (DPC) membrane is
                                                            recommended that they be constructed using
    recommended for use with CSR Hebel walls. They
                                                            100mm thick blocks and filled with 200mm x
    are used mainly to prevent damp rising in masonry.
                                                            100mm concrete to the footing and roof system.
    However, they will also serve to minimise damage
    caused by movements due to thermal expansion,
    shrinkage, creep and foundation movements.

                                                                                    CSR HEBEL TECHNICAL MANUAL
                                                                                             VERSION 1 – JUNE 2001
                                  CSR Hebel Block Design & Construction
6.4 Movement Control Joints                         The project architect and engineer should be
                                                    involved in the locating of control joints. The
To minimise cracking in walls caused by thermal
                                                    recommended maximum distance a control joint
expansion, contraction, foundation movement,
                                                    should be located from a corner or return is shown
drying shrinkage etc. joints should be located in
                                                    in Figure 6.1.
accordance with the joint spacings shown in Table
6.1.                                                For further guidelines and comprehensive discussion
                                                    on articulation refer to Cement & Concrete
Table 6.1: Maximum Joint Spacings
in Block Walls                                      Association of Australia, Technical Note 61 (Dated
                                                    Oct. 1991.).
 Wall/Footing Design         Joint Spacing
                                                    Unless otherwise designed by a structural engineer,
 Articulated or
                             6m            max      control joints require shear connectors placed across
                                                    the joints to maintain stability of the walls. Maximum
Notes                                               vertical spacing of connectors is 600mm. Refer to
1. Joint width approximately 10mm minimum.          Detail W2 on page 6.79.
   Refer for Detail W1 on page 6.77.                Attention should be given to ensuring that these
2. Joints should be included in all walls, both     joints are kept free of all debris and mortar. In no
   internal and external.                           circumstances should a movement control joint be
                                                    rendered across.

Figure 6.1: Locations for Control Joints


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