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A wall, a building, or in between?

On two separate occasions, the Ministry of Building, Innovation and Employment (MBIE) has judged that retaining walls are buildings – which provides an important lesson to landscapers around the country

In the first instance, a determination found that a 2m high wall made of ponga logs, built to replace a section of an existing wall, did not comply with Building Code clauses B1 Structure and B2 Durability, despite protests from the owner that the Building Act did not apply to the ponga log wall.

The battle over the retaining wall first started in 2021, when a neighbour raised concerns to Taupō District Council about the wall Peter Paalvast was building. After an inspection in January 2022, Paalvast was told he’d need a building consent to continue his works to replace sections of an existing ponga log wall with new ponga logs.

Palvaast disagreed, stating that he was planting the ponga logs rather than building a wall from them – despite photographic evidence that side stalks, fronds and roots were removed from the logs and that they’d all been sawn to a uniform length.

Additionally, it was unclear whether the logs had been embedded into the ground at any depth. Furthermore, Pavaast undertook excavation work on the ground next to the ponga wall.

“The excavation appears to have been in two steps; there is a narrow trench immediately alongside where the logs have been installed, which rises to an embankment. The excavation is not uniform, and the narrow trench does not appear to continue the full length of the new wall. The embankment rises to approximately 1.1m above the ground-level of the neighbours’ property,” wrote MBIE’s Manager Advisory, Building Resolution Andrew Eames in the determination published about the case.

Despite being issued five notices to fix between January and September 2022, work continued on the installation of the ponga logs. In October 2022, Taupō District Council asked a firm of consultant engineers for guidance on whether the material was suitable. The engineers said there were “no guidance documents” for ponga retaining walls and concluded ponga would fail requirements of B1 and B2.

“They should be used for landscape garden fencing only,” said the firm.

Interpretation rejected

Following advice from the consultant engineers, the Council asked Palvaast to reduce the depth of ground being retained, which he rejected on the basis that his wall was “a planting activity”.

“The owner stated their view that the Building Act ‘clearly does not apply to our activity’. The owner stated the purpose of the Act is to ensure that people who use buildings can do so safely, without endangering their health, and there was no evidence that people using the wall could not do so safely or without endangering their health. The owner also disputed whether ‘punga (sic) plantings’ could be considered a retaining wall, building, building work or sitework,” said Eames.

This reasoning was rejected as “there is no requirement for people to have actually suffered injury or loss of amenity, or for other property to have actually suffered physical damage” under clause B1, continued Eames.

The Council then issued Palvaast with a “path to compliance” and highlighted how Act sections 7, 8,14B, 14E and 19 applied to the wall and how that required him to comply with B1 and B2 of the Code – which was rejected by Palvaast. 

At this stage, the Council involved MBIE by applying for a determination from the ministry. MBIE concluded it wasn’t satisfied that the wall is compliant as, among other things:

Compliance of a retaining wall can’t be achieved via use of B1/VM4, as those documents don’t include ponga logs as engineering material.

Ponga logs can’t be employed as an alternative solution because there are no test methods or calculation pathways, which can verify ponga logs as structural retaining wall members.

The wall hasn’t been in place long enough to satisfy compliance through ‘in-service history’.

CPEng structural engineers opined that ponga walls are not structural members.

Palvaast countered by claiming the Council and MBIE had misinterpreted the Act and said ponga material was not building material and claimed it was “similar to hydroseeding”.

The determination

As ‘retaining wall’ is not defined by the Act or Code, MBIE considered the dictionary definition of ‘serving to retain or hold by physical force or resistance’.

MBIE also rejected Palvaast’s insistence that the ponga wall was similar to hydroseeding.

“I do not consider that securing 2m long ponga logs to timber rails with wire to protect a vertical earth face is comparable to hydroseeding the sloping face of an embankment, which is inherently stable,” wrote Eames.

Eames also said that he considered the “earth behind the ponga wall would not be inherently stable and would require lateral restraint from the ponga wall”.

He added that the homeowner’s intention is to “reinstate the earth behind the wall”. As a consequence, the ponga wall performs the function of a retaining wall. 

Palvaast’s case was not helped by the fact that he refused to provide MBIE with any plans or additional information about the wall, which led Eames to come to a conclusion based on site visits and photos.

After assessing the evidence, Eames concluded that the structure is a building, despite Palvaast’s insistence that it was not, and that it did not comply with clause B1 and B2.

The wall, which is now officially deemed as a retaining wall, is now subject to further notices to fix from Taupō District Council.

Is a retaining wall a building?

While it might be surprising, retaining walls are often classed as buildings, and was also the case in another determination recently brought by the owners of the property in response to Thames-Coromandel District Council stating that a timber barrier on top of?  a retaining wall did not comply with clause F4 Safety from falling. 

The owner believed that the retaining wall and barrier did not meet the requirements of a building, and therefore the barrier did not need to comply with F4 Safety from falling.

In deciding the matter, MBIE Principle Advisor Determinations Peta Hird considered whether the retaining wall is considered a building under the Act and, assuming it was, whether it complied with clause F4.

Hird found that the retaining was classified as a building, as it is a “permanent and immovable” structure, which meets the definition of a building as written in Section 8(1)(a) of the Building Act 2004. Hird added that “the Building Code clause A1 Classified Uses supports this interpretation”.

Actions to be taken

Responding to questions from NZ Landscaper, a Taupō District Council spokesperson said Palvaast could be issued with a fine “not exceeding $200,000” and, in the case of a continuing offence, a further fine “not exceeding $20,000 for every day or part of a day during which the offence had continued” if he did not respond to the latest notice to fix. The Council could also bring an infringement fee of $1,000 against him, added the spokesperson.

“Enforcement options available to a territorial authority under the Building Act include prosecution, issuing infringement notices or carrying out the necessary work and recovering the costs,” continued the spokesperson. “Additionally, a territorial authority may issue a dangerous building notice where a building posesa risk to public safety. This would require a building owner to take immediate action to remedy the situation.”

The spokesperson concluded by stating that these consequences serve as a deterrent to individuals who are tempted to ignore notices to fix and continue noncompliant construction work.

At the time of publication, the retaining wall no longer in question has not been fixed, and no fines have yet been issued. 

The property owners in Thames-Coromandel had yet to address the situation, said Building Unit Manager Corinne Hamlin.

“In line with the determination finding, the property owner now has the opportunity to remediate the barrier to comply with the Building Code. As a territorial authority, we are committed to maintaining a safe built environment for our community. We encourage the owner to comply voluntarily and will assist them to understand the requirements of the Building Code.  

“In cases where voluntary compliance is not achieved, Council may enforce compliance where necessary.” 


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