People across Kent have been asked to contribute £1 to the appeal to save Canterbury's crumbling cathedral.
Scaffolding is already up in the building with a survey under way
Fundraisers at the 900-year-old cathedral, which is suffering from age and pollution, said £1m raised on Friday "would make a real difference".
"Unless the campaign raises £50m over the next five years, the people of Kent could face a future without their Cathedral," spokesman David Innes said.
Scaffolding is already up at the World Heritage Site as repairs take place.
A £50m fundraising drive began in October for the building in Kent and individual donations alone raised more than £300,000 in the first month.
Previous renovation projects were paid for by fundraising appeals about every 30 years.
When the campaign was launched, it was revealed that the roof had serious structural problems resulting from repairs after World War II, when supporting beams were encased in concrete.
The building's south side also had a "serious hidden defect" resulting from war damage - a fireball from a bomb dropped in 1942 created a vacuum which pulled out the outer limestone skin of the cathedral and sand and cement used to fill the void were now causing damage.
The materials were the only ones available at the time.
Half the 1m visitors to the cathedral every year pay entrance fees, but they just cover the annual running costs of the building.
Trusts and charities have expressed an interest in getting involved with the fundraising, the cathedral said.