Retaining walls and garden structures in Queensland
Queensland’s Building Regulation 2021 has a provision for retaining walls that turns on three conditions together: no surcharge loading over the wall’s zone of influence, a total height of wall and retained fill or cut of no more than 1m, and a distance of at least 1.5m from a building or another retaining wall. The same regulation sets conditions for cut and fill, fences and small structures, quoted below in its own words.
General information, not legal or building advice. The regulation itself, listed at the foot of this page, is the text to check before relying on any figure here.
Retaining walls
The retaining wall conditions
The provision is headed “Work for particular retaining walls”. Its three conditions are joined by “and”, so all three hold at once:
“(1) Building work for a retaining wall, other than work for a retaining wall that forms part of the fencing for a regulated pool, if”
- “(a) there is no surcharge loading over the zone of influence for the wall; and”
- “(b) the total height of the wall and of the fill or cut retained by the wall is no more than 1m; and”
- “(c) the wall is no closer than 1.5m to a building or another retaining wall.”
The provision defines four terms; two of them, in its words:
- Total height
- “total height of the wall means the height of the wall measured from the finished ground level.”
- Zone of influence
- “zone of influence, for the retaining wall, means the volume of soil stratum behind the wall that affects the wall’s structural integrity.”
So the 1m is not the height of the wall alone: it counts the fill or cut the wall holds back, and the wall is measured from the finished ground. The provision also defines surcharge loading and finished ground level; read those definitions in the regulation, linked at the foot of this page, before relying on the first condition.
Where a wall meets all three conditions, or misses one, the regulation itself says what follows; this page quotes only the conditions. Read the full provision in the regulation, linked at the foot of this page.
Cut and fill
Cutting into the slope, or filling it
Levelling a sloping block can mean digging out one part and filling another. The regulation has a separate provision for “Building work that is filling or excavation for a building or structure if”, and two of its conditions are:
- “(a) the proposed cut or fill is no deeper than 1m above or below the natural ground surface; and”
- “(c) any fill embankment is no steeper than 4.0 horizontal to 1.0 vertical; and”
A selection: the provision has conditions (b) and (d) as well, on cut and compacted fill embankments by soil type, in the regulation linked at the foot of this page.
Fences
Garden fences up to 2m
“(1) Building work for a fence, if the fence is”
- “(a) no higher than 2m above the fence’s natural ground surface; and”
- “(b) not for a regulated pool.”
Height here is measured from natural ground, while the retaining wall’s is measured from finished ground. A fence on top of a retaining wall is worth checking against both provisions.
Small structures
Sheds and other small structures
The regulation also has a provision headed “Other work for class 10 buildings or structures”. It covers building work for a class 10 building or structure that meets the size requirements in its subsection (2), and it leaves some work out. The work subsection (1) leaves out, in full (subsection (3) sets one more limit, in the regulation):
“(1) Building work for a class 10 building or structure that meets the requirements of subsection (2), other than building work”
- “(a) within Wind Region C (tropical cyclone area) mentioned in AS 1170.2-2011 ‘Structural design actions Wind actions’; or”
- “(b) for a rainwater tank for a new building; or”
- “(c) for a deck that is roofed or higher than 1m above the deck’s natural ground surface; or”
- “(d) for a regulated pool or its fence; or”
- “(e) for a solar hot water system or photovoltaic solar panel.”
Two of the three size requirements in subsection (2) are a plan area of no more than 10m² and no side longer than 5m. The third sets limits on what the structure has above its natural ground surface, including a height of no more than 2.4m; read it whole in the regulation before relying on it.
Pool fencing
Where each provision leaves the pool out
Each of these provisions sets pool work aside in its own words: the retaining wall provision excludes “a retaining wall that forms part of the fencing for a regulated pool”, the fence provision covers a fence “not for a regulated pool”, and the class 10 provision leaves out work “for a regulated pool or its fence”. The pool barrier has rules of its own, set out in the guide to pool safety barriers in Queensland.
Who builds it
The QBCC’s structural landscaping licence class names “retaining walls of a height that do not require an engineering certification under a local law” in its scope, alongside fences, decking and pergolas, and prefabricated sheds with a floor area of not more than 10m². The guide to when landscaping needs a QBCC licence sets out the $3,300 threshold and the rest of the class.