Rotorua Museum – A complex process
Monday, 13 August 2018
Roof tiles have been a hot topic amongst the team working alongside Heritage New Zealand on the upcoming restoration of Rotorua Museum.
The need to maintain the heritage integrity of the building means every aspect of the work to be undertaken must be carefully considered.
It is coming up to two years since the museum, housed within the iconic Bath House building, had to be closed to the public following a seismic assessment that identified the building as earthquake prone. That was the start of a long and complex process to bring this beloved Heritage 1 classified building back to life.
While from the outside there may have appeared to be little happening, there was a lot going on in the background. Extensive structural and geotechnical assessments were needed, complex work which required particular expertise and a lot of care given the building’s heritage status.
Once the extent of the work that would be required to restore the building was known, Council was able to start making decisions on the way forward.
Work planned will see the building will be earthquake strengthened, the impacted heritage features reinstated and visitor experience optimised.
The architectural concept design which is being finalised has seen a collaborative approach to all decisions with input from engineers, architects, heritage architects, geological experts and museum staff.
The next phase will be developed design and in anticipation, the process of early contractor engagement and recruitment of a project manager has begun. Construction is due to begin in 2019 with proposed completion in 2021.
Each design decision for the building has been carefully assessed and researched to ensure it meets all requirements including maintaining the heritage look and feel, ensuring structural competency and architectural aesthetics while considering ongoing costs and maintenance.
The Bath House roof tiles are just one example of the complexity of this process and the considerations involved.
The current clay tiles weigh just over 164 tonnes and make up a large part of the weight sitting on the compromised building frame. Clay tiles are glazed however high levels of hydrogen sulphide corrodes the glaze and makes the tiles more porous. The tiles then absorb water easily making them weigh up to twice as much after heavy rain. These environmental factors also make the tiles brittle.
The team is researching lightweight alternatives such as composite and aluminium tile.
Robin Byron, a Conservation Architect from Heritage New Zealand, says from a heritage perspective the ideal is to replace like-for-like but because of the weight of the clay tiles, and the degradation experienced, in this situation alternatives are being considered.
“The weight is a significant factor because a lighter tile means that the needed structural strengthening work can be achieved with less intrusion into the building affecting the important heritage features and fabric. Retaining the integrity of the roofing material itself is important for ensuring weather proofing of the building, safety (from falling tiles), and the minimising of ongoing maintenance and repairs.”
Ms Byron says it’s critical the selected alternate tiles have the same colour, profile and appearance as the existing clay tiles. “The Rotorua Museum roof is such a visible and iconic feature of this supremely significant heritage place.”
There would be cost benefits to having a lightweight roof as it would reduce structural steel requirements and reduce the impact of damage to the heritage fabric of the building. A composite or aluminium tile could also have a longer lifespan, compared to the current clay tiles that have not performed as well as anticipated.
While efforts to resolve the roofing issue continue, work towards finalised architectural concept designs is also ongoing and will be presented to Council in the near future. The next phase, developed design, can then be undertaken.