Canberra are confident their first-ever home NRL preliminary final will sell-out in just 24 hours, after more than 20,000 tickets were sold in five hours on Monday.

With a club-record home crowd expected, the Raiders’ only regret is likely not being able to meet the demand for Friday night’s clash with South Sydney.

The Raiders initially hoped to set a ground attendance record but can’t quite eclipse the 28,753 fans who watched the Super Rugby final between the Brumbies and Crusaders in 2004 because the GIO Stadium capacity has been reduced since, even with temporary seating added.

The Green Machine are, however, expected to push past their record 26,476 in attendance for the NRL semi-final between the Raiders and Wests Tigers in 2010.

“I’m confident it will be a sell-out either today (Monday) or tomorrow morning,” Raiders boss Don Furner told AAP.

“With the standing room availability and some temporary seating, I think it’ll get to about 28,000 which is the maximum it can be.

“It can never get to what the ground record is back in 2004 because they reconfigured the stadium and took seats out.”

Furner said it was the biggest home game in the club’s history and he backed Canberra’s famous pre-game Viking clap to be their loudest on record.

“I’m sure it will be, it’s our biggest crowd ever and our most important home game in club history,” Furner said.

“We’ve sold 20,000 tickets since 10am and if we had 35,000 seats I think it would still sell-out.”

The Raiders are playing for a spot in their first grand final since 1994.