A Rotorua Lakes Council spokesman said the tiles showed the original partition layout of the bath area and dated back to when that section was built in 1908.
The tiles were in three areas of the museum.
“The current structural strengthening design for the museum utilises the cafe floor space where the tiles are and we are looking at options for managing this issue.
“Impacts on design and costs won’t be known until we have established what the options are, but we do not anticipate it to have a major impact on design and costs.”
The council, which is co-funding the project with several other contributors, announced in April it had secured the final funding needed and awarded the construction contract to Watts & Hughes – the company that managed the museum’s south wing extension, which was completed in 2011.
The council said in April the expected cost was $73.55m.
Construction began in June.
The museum used to attract about 100,000-120,000 visitors each year.
An Infrastructure and Environment Committee meeting agenda said works in 2025 would be focused on finishing all structural works to enable building fit-out to take place in 2026.
It is expected the museum will reopen in 2027.
Laura Smith is a Local Democracy Reporting journalist based at the Rotorua Daily Post. She previously reported general news for the Otago Daily Times and Southland Express, and has been a journalist since 2019.
- LDR is local body journalism co-funded by RNZ and NZ On Air.