The issue was identified as part of an annual maintenance programme implemented by Wellington City Council following major restoration work undertaken on The Cenotaph - also known as the Wellington Citizen's War Memorial - in 1997.
The Council's Projects Officer, Vikki Muxlow, says it has been 12 years since restoration and natural wear and tear has taken its toll.
"Through the maintenance programme it has been identified that the mortar between the marble blocks in the column is in need of repair to keep the structure waterproof and sound. Contractors Salamander Restoration will remove all of the existing jointing and replace it."
Weather depending, contractors will begin erecting scaffolding around the column tomorrow with work expected to take up to six weeks. There will be no services held at the Cenotaph during this time.
The Cenotaph was built in 1929 as a memorial to Wellingtonians who died in the first World War. It was rededicated in 1952 to commemorate those who died in the second World War.
A report at the time of the Cenotaph's construction said the sculpture represents "victorious youth mounted on the winged horse Pegasus and looking to heaven for strength and wisdom to make worthwhile the sacrifices represented by the shrine below".
The memorial is listed as a heritage asset within the Wellington City Council District Plan and is also registered with the New Zealand Historic Places Trust.