With concrete firms in Wanaka and Queenstown on standby, Cromwell crews started pouring the concrete at 6pm on Wednesday, and continued the work throughout the night.
Mitre 10's Cromwell owners, Toby and Glenda Templeton, said they hoped their multimillion-dollar hardware complex would be completed and opened by Easter next year.
Its concrete floor comprised 800 tonnes of gravel, 124 tonnes of cement, 40,000 litres of water, and was mixed and poured using a total of 10 concrete trucks from firms in Oamaru, Cromwell, Wanaka, and Queenstown.
About 40 people were involved in the exercise, which took place overnight while temperatures were cool enough for the concrete to be levelled and smoothed before it dried.
Mr Templeton said the building should be up by the end of January and it would take at least six weeks to fit and stock its interior.
