All Auckland train lines will be closed for maintenance over Labour Day weekend, AT says, while KiwiRail has apologised to the city's commuters.

The work will begin late Friday evening and won't finish until Monday, with buses replacing trains throughout the city's network.

KiwiRail chief operating officer David Gordon said the public holiday is the perfect opportunity to get out onto the tracks for work that takes time to complete due to the low rate of patronage.

Three days of uninterrupted work will be used to extend electrification to Pukekohe and continue building new stations to support housing growth around Drury.

Improvments to the southern line, including building a third main line in the busiest section in South Auckland to relieve congestion by separating commuter and freight trains will also be conducted. Work will be carried out 24/7 in some areas, KiwiRail said.

Gordan said these projects will help maximise the benefits of the future City Rail Link across Auckland and reduce carbon emissions in the city.

"Passengers will enjoy better access to the network as well as faster, more frequent services. The improved network will also provide more resilient, faster freight services and support more Kiwi businesses putting their goods on rail," Gordan said.

"It is challenging to get these transformative projects done on a live network with trains running day and night. We understand that halting trains will impact the city's train users and apologise for this."

During Labour weekend teams will be working at multiple locations including Waitematā (Britomart); Newmarket; Westfield and Wiri Junctions; between Papakura and Pukekohe and at Pukekohe Station.

City Rail Link works will continue at Maungawhau/Mt Eden; earthworks, tree-trimming and some non-native tree removal will also be done within the rail corridor from Quay Park (by the entrance to Ports of Auckland alongside Tamaki Drive).