The NZ Transport Agency will begin strengthening the timber deck on the 102-year-old bridge on Tuesday.
The installation of scaffolding under the bridge on Tuesday means it will be closed for the entire day.
Once the scaffolding is erected, the strengthening work will take place overnight to minimise disruption to motorists. Detours will be in place between 8pm to 6am, Monday to Thursday.
The bridge will be opened on the hour every hour for drivers who are happy to wait to cross.
Detours via Camp Hill Rd will be in place and motorists will be re-directed with electronic message boards. NZTA senior network manager John Jarvis said it would take up to a month to complete the upgrades.
The work involved installing additional timber beams underneath the deck and replacing up to 650 bolts. About $135,000 will be spent strengthening the bridge.
New safety barriers will also be installed on the approaches to the bridge, costing a further $90,000.
