Auckland's Mangere Bridge is shut to all northbound traffic until tomorrow as a double-strength repair crew toils round the clock to fit two heavy joints to the structure.

Contractors to Transit NZ have brought in four work teams to fit the 10-tonne replacement expansion joints simultaneously, to hasten the bridge's reopening by 11am or noon tomorrow.

Both northbound lanes were closed around midnight last night to allow the first two teams of riggers, fitters and welders to begin work.

Their schedule has been accelerated compared with last month, when lane closures caused traffic jams to spiral through streets several kilometres south of the bridge, forcing a four-week adjournment as Transit overhauled traffic management and communication strategies.

Both southbound lanes will remain open throughout the project - which will continue for the next two weekends if weather permits - but Transit says even motorists heading in that direction such as to the airport should allow at least an hour's extra travelling time.

Instead of relying on just one detour, which last time became clogged well before a fatal truck accident made things even worse, Transit is offering two main detours from the airport.

These will be monitored by staff on motorcycles and varied if they become jammed, particularly during an airport traffic peak from mid-morning until about 2pm, when up to 3200 vehicles an hour normally head north across Mangere Bridge.

Transit northern operations manager Joseph Flanagan said patchy weather should not be too much of a problem, as work could continue in light showers, but MetService forecasters had warned of possible wind and rain ahead of Cyclone Wati from late tomorrow.

He was confident workers would be well off the bridge by then, although Auckland City Council contractors hope to complete their resealing of a heavily used kilometre of Hillsborough Rd tomorrow night after rain forced a delay from Thursday night.