Attachment 4 - Site Investigation and Slab Report

                      Likewise, the principles apply in mine subsidence    movement. Measures intended to provide more
                  areas (particularly in areas where long-wall mining      consistent foundation conditions include:
                  methods are used) as the ground movements are            ■ Draining surface water away from the building to
                  similar to those encountered on reactive clay soils.        prevent ponding adjacent to footings.
                  However, items such as the required joint width and      ■ Providing ‘apron’ paths around perimeter walls
                  spacing will need to be calculated to confirm that          to better control and provide more consistent
                  the details contained herein are appropriate for the        moisture levels within the soil adjacent to the
                  expected ground movement.                                   footings.
                      While articulation joints normally apply to          ■ Avoiding large trees or thick shrubbery nearby
                  masonry walls, framed walls (referred to as clad            that locally draw moisture from the soil and
                  frame in AS 28701) which are more flexible than             cause uneven and often large soil movements.
                  masonry walls may also benefit from articulation.        ■ Providing flexible drainage connections to
                  The location and spacing of articulation joints for         prevent water leakage near footings.
                  clad frame walls are similar to those recommended
                  for masonry walls.                                          These and other practical measures are
                      While every individual situation where an            outlined in Foundation Maintenance and Footing
                  articulation joint is required can not be covered        Performance: A Homeowner’s Guide3.
                  because of the variety of wall and window/door
                  opening combinations, this document provides             3        FOUNDATION AND BUILDING MOVEMENT
                  guidelines for the location and detailing of             The foundation is the ground that supports the
                  articulation joints.                                     building and the footing is the construction
                                                                           (concrete slab, strip, pad or piers) which transfers
                  2         INTRODUCTION                                   the load from the building to the foundation.
                  Masonry walls – whether built of bricks or blocks,            Footings may be designed to either restrict
                  made of fired clay, concrete or sand/lime – are          or accommodate movements that occur in the
                  rigid and brittle. They can thus tolerate only minor     foundation soil. For small buildings constructed on
                  footing movement without cracking and/or causing         soils that shrink or swell (reactive sites) it is usually
                  windows and doors to become jammed.                      uneconomical to attempt to design a rigid footing
                       Unpainted masonry walls incorporating cement/       system to avoid transmission of any significant
                  lime mortar are the most tolerant of movement,           movement to the superstructure. It is better to
                  and any cracking in the mortar joints tends to be        design the footing system to allow a limited amount
                  inconspicuous. In rendered and/or painted walls,         of movement, and a superstructure that can tolerate
                  cracking may be visually unacceptable, even though       that movement.
                  structural performance is unimpaired.                         Generally, the more reactive the soil is the more
                      The solution is to provide footings that are rigid   rigid the footings need to be in order to ensure the
                  enough or to articulate the walls; the latter will       acceptable performance of the structure above.
                  usually be the more economical solution as more          If brittle elements such as masonry walls which
                  flexible footings can be used. Articulation involves     are susceptible to cracking due to movement are
                  dividing the walls into panels separated by vertical     articulated, the risk of cracking will be minimised,
                  joints that allow movement and thus reduce the risk      and less-rigid footings than those needed for
                  of cracking.                                             non‑articulated buildings will be adequate.
                       Footing movement is typically caused by                  Deemed-to-comply or standard footing systems
                  swelling and shrinking of the foundation material.       for soils of varying reactivity are detailed in AS 2870.
                  Thus the risk of movement depends on the extent          Apart from full masonry on Class H sites, for which
                  to which the foundation soil reacts to changes           articulation is mandatory, options are given for
                  in moisture content. AS 2870 classifies sites in         either articulated or non-articulated masonry
                  accordance with the soil’s reactivity in a range from    construction for various site classes. On stable sites
                  Class A (stable) to Class E (extremely reactive). The    (Class A) and slightly reactive sites (Class S) no
                  Building Code of Australia (BCA)2 requires that          concession in footing size is allowed for articulated
                  houses on all sites other than Class A and Class S       masonry veneer walling. On Class S sites there is a
                  (slightly reactive) incorporate articulated walls.       concession for articulated full masonry. Note that
                       It is important to note that articulation of the    the acceptable construction provisions of the BCA
                  walls of a building does not replace the need to         require articulation on all site classes other than
                  adopt other measures which are essential when            Class A and S.
                  building on reactive-soil sites to further reduce the
                  risk of cracking to masonry walls from foundation


Page 2 Articulated Walling