Mr Findlay, of Dunedin, was one of 42 people involved in a Red Cross Emergency Response Team training camp for new recruits at the Otago Youth Adventure Trust-owned lodge.
Just after 6am on Saturday, he heard "a rumble and a bang" against the back wall of the room in which he was staying with his wife, Rhonda, and daughters Eliza (12) and Sarah (10).
The volunteer shone a head torch outside and saw a wall of clay at the door.
Mr Findlay immediately roused his family and got them out before knocking on doors of other rooms and yelling for people to get out of the building.
"That's what we train for, but it took a while for some people to realise this was for real."
The campers had "a lucky escape", he said. "I was nervous, but in hindsight I should have been more nervous than I was at the time."
The buildings had moved only after the group, which included children and a baby, had evacuated in various states of dress - some were in pyjamas and underwear and many were without any kind of footwear - to a nearby garage.
They were soon met by camp warden Jenny Scott, who had been woken by fire alarms. The group were driven in vehicles back to her nearby house, where they stayed for several hours and had breakfast before being driven back to Dunedin. Some were taken back to the city by the Otago Daily Times.
Lynette Will, who had felt uneasy about the heavy overnight rain and, struggling to sleep, got up about 4am, said things had gone "very smoothly".
"We were very lucky Nathan spotted it," she said.
Most of the campers had initially thought it was a training exercise, she said.
Anya Matravers (17), Jacob Moller (19), Jill Hetherington (25), Daniel Benn (18) and Amy Moffitt (18), who were all part of the training group, agreed.
However, creaking and cracking noises soon convinced them they were in a real emergency situation.
All five were "definitely" planning to continue their Red Cross training despite the dramas of the camp.
However, Mr Findlay did have at least one concern. He was wondering how he would unlock the door to his Dunedin home, given the house keys were in his Safari, under the partially demolished camp building.
The Red Cross team returned to the lodge yesterday afternoon to remove as many of their personal items from the rooms as could be done safely.