Probably the majority of residential buildings below 4 storeys and many buildings of high-rise construction (greater than 4 storey) feature external and/or internal walls of clay brick masonry.
They fall into 2 main categories that are either full brick cavity construction or brick veneer.
Cavity construction consists of 2 skins of brickwork tied together with metal ties, brick veneer consists of timber or metal framed construction faced with a skin of brickwork, which is tied to the frame with metal ties.
In both cases the inner skin of brickwork or timber carries the vertical load, the outer skin is primarily for weather resistance and décoration. It is important to note, however, that the outer skin is an integral structural component controlling lateral stability and the ability of the inner skin to carry the vertical load.
There appears to be an upsurge of claims relating to the structural capacity of brick faced construction or to the unsatisfactory appearance of the walls forming the structure. In addition that that one would have to consider frequent complaints about cracking to internal masonry and cracking affects on aesthetics.
Assessments are frequently put forward by building experts in matters before relevant Forums where structural assessment and aesthetic appeal are conflated to a subjective opinion based upon nothing more than the expert’s personal preference or incorrect referencing to allowable damage criteria set out in Appendix C of AS 2870-2011 “Residential slabs and footings” (AS 2870).
Notwithstanding that any decision made can only be as good as the evidence produced, knowledge of the evaluative process should assist the decision maker particularly when contemplating a work orders or damages.
When looking at masonry performance, the assessment criteria should consider a range of approaches that may be adopted to determine whether or not masonry construction meets the:
- Aesthetic performance requirements;
- Structural performance requirements;
- Deemed-to-Satisfy Solutions; and
- Fit for Purpose requirements.
In the context of the Building Code of Australia (BCA):
- Deemed-to-Satisfy Solution is an “off the shelf” design recipes which meet its Performance Criteria and is intended for use as a means of achieving mandatory compliance.
An assessment and approval criteria, integrated in the Environmental Planning and Assessment Act 1979, the Building Professional Act 2005 and in the new the Design and Building Practitioners Act 2020, adopts Deemed-to-Satisfy Solutions as a default building solution, intended to meet BCA Performance Requirements.
- Performance Solution is a design solution that does not meet the requirements of a Deemed-to-Satisfy Solution, however is appropriately assessed pursuant to required Verification Methods detailed in the BCA.
- Fit for Purpose is best defined as a Performance Solution developed in accordance with BCA Clause A2.2 of Volume One or Clause 1.2.2 of Volume Two and documented pursuant to the relevant ABCB protocol.
In reality, when assessing the need for rectification or damages the “real issue” in dispute must be addressed.
Apart from BCA Volume Two, three Australian Standards define masonry units and their use in structures:
- AS 3700 Masonry Structures, provides the basic rules for the design and construction of masonry structures;
- AS 4773, Parts 1 and 2 Masonry in small buildings, details specific requirements for Class 1 buildings with a maximum height of 8.5m; and
- AS 4455 Masonry Units, Pavers and Flags has three parts – Masonry Units, provides for manufacturing and testing of masonry units.
It should, however, be noted that AS4455 is not a primary reference under Schedule 4 of BCA Volume One or Two. This Australian standard is referenced by AS3700 and AS4773 as a materials supply standard, hence, this standard is considered to be a guide or a reference standard complementing the primary reference documents.
For this reason, the requirements and limitations of AS4455 do not take precedence over the Deemed-to-Satisfy Solutions provided by AS3700 and AS4773.Most importantly, damage criteria set out in Appendix C of AS 2870 should not be used when assessing damage to masonry elements. AS 2870 assessment criteria is intended to for masonry damage from foundation movement of Class 1 building constructed on the specific type of footings and not for general assessment of acceptable masonry performance or aesthetics.