The sealed car park opposite the historic 1914 rest house will also be upgraded.
The project is an initiative of the Summit Road Society, a charitable organisation set up in 1948.
The lookout will be named after John Jameson, the grandson of Harry Ell who founded the society. He died in 2018, aged 97.
The car park was closed this week so contractors can prepare the site and begin work on Monday.
It will remain closed for the construction period, which is expected to take up to four months, depending on the weather.
Pedestrian access to the tracks will be maintained and alternative parking is available at other parking bays and car parks along the Summit Rd.
The lookout will feature stone walls and native plantings, a pou whenua area, educational panels and a plaque commemorating the work of society founder John Jameson.
Funding of $150,000 has come from Christchurch City Council’s capital endowment fund, with the remainder of the costs raised by the society, which is managing the project.
Banks Peninsula Community Board chairwoman Tori Peden said the new lookout will capture spectacular views of the harbour.
"For a number of years now the society has been working to create a lookout and heritage education area here," Peden said.
"We’re pleased to have been able to work in partnership with them to help bring this special project to fruition.
"I’m looking forward to seeing the finished result in a few months’ time and ask the community to bear with us while the work is carried out and car park is closed.
"The end result will be worth it."
Work was due to start in February but was delayed due to the Covid-19 outbreak.
