Attachment 4 - Site Investigation and Slab Report

                                         Return wall                             Return wall required                   300
                                         required for                            for lateral restraint                  max.
                                         lateral restraint




                                      Articulation joint
                                      with sliding ties                   Articulation joint             Articulation joint
                              INCORRECT 7                         CORRECT 3                                                   CORRECT 3

                  Figure 17 Location of articulation joints to maintain stability


                  7.1.1 Minimum Width                                          Sealants should be applied towards the end of
                  The minimum width of articulation joints should              the construction after any initial movement has
                  take into consideration the height of the wall and           occurred.
                  the expected movement, especially if the joint is to             For clay bricks which tend to grow, sealants
                  serve the dual function of articulation and expansion        must allow for long-term, permanent compression;
                  or contraction. Table 2 gives suitable joint spacings        for concrete or calcium silicate bricks and blocks
                  for both 10- and 15-mm-wide joints for walls up to           which tend to shrink, the sealants must allow for
                  8.5 m high.                                                  long-term tension.
                      The joint widths in Table 2 will also                        The geometry of the sealant is important to
                  accommodate some expansion or contraction of                 ensure that the material is able to comply with the
                  the masonry wall panels. Designers and builders              stated performance. If the depth of the sealant is
                  should, however, consider whether there is potential         too great it will act more like a rigid ‘block’ than a
                  for greater movement than can be accommodated                thin elastic member and will not be able to extend/
                  by a 10- or 15-mm joint width, eg in mine                    contract properly. Generally, the depth of sealant
                  subsidence areas. Where the control joint functions          should not be more than the joint width for joints up
                  both as an articulation joint and an expansion               to 12 mm in width, and no more than half the joint
                  joint, either the overall width of the joint should          width for wider joints. The joint filler or a backer
                  be increased to 0.7 times the sum of the required            rod, are typically used to provide the correct joint
                  widths for each separate function, or the joint              geometry. The manufacturer’s recommendations
                  spacing should be reduced for the 10- or 15-mm-              should be followed for each specific material.
                  wide joints.                                                 Note that sealants may need to be replaced every
                                                                               10 to 15 years (depending on type and exposure
                  7.1.2 Joint Sealants                                         condition) as part of building maintenance.
                  Sealant materials typically include silicones and                Where articulation joints occur at the ends of
                  polyurethanes. For painted finishes, either a                lintels (ie at the sides of window/door openings)
                  specialist silicone sealant that can be painted, or          and movement of the lintel along the bed joint
                  more commonly, a polyurethane sealant should be              is expected, this joint may also be sealed as the
                  used. Polysulphide materials (able to be painted)            movement will typically cause cracking and loss of
                  are also available but as they are two-component             the mortar from the joint Figure 22.
                  products, they are not commonly used. Sealants                   If the wall of a Class 1 building (house) is located
                  should have a minimum extensibility of 50%                   closer than 900 mm to a property boundary (other
                  (ie ±25%) and be suitable for the clay or concrete           than a boundary adjoining a road or other public
                  masonry walling material used. Some sealants may             space), the BCA requires a fire resistance level
                  require priming of the joint to promote bonding to           (FRL) of not less than 60/60/60. However, the BCA
                  the substrate. Sealants are gunned into the joint            states that small openings in the masonry such
                  and are available in a variety of colours, either to         as sub‑floor vents, weepholes and control joints
                  match the masonry or mortar colour to assist in              (including articulation joints) do not need to be fire
                  reducing the visual impact of the joint. It is also          rated. For fire separating walls of attached Class 1
                  possible to dust the surface of freshly applied              buildings and other building types, the use of a
                  sealant with crushed mortar, thereby giving it a             fire‑rated sealant in articulation joints should be
                  texture and colour that closely matches the mortar           provided. For such buildings, the sealant may also
                  joints in the surrounding brickwork. Note that               need to provide acoustic performance.
                  sealants and/or filler materials should be recessed
                  back from the outside face to prevent the sealant
                  being squeezed out of the joint if the maximum
                  expected compression of the joint occurs Figure 21.


Page 12 Articulated Walling