There were no injuries reported.
Fire crews left the scene about 6.30pm and a fire investigator and police were due to return to the address today.
Braemore Lodge managing director Luke Harding said the facility had provided community and residential services to Lakes District Health Board for the past 24 years.
"The facility that was damaged yesterday was a 24/7 staffed service. The fire has significantly damaged a large portion of our Lodge at 4 Te Manga Pl.
"We plan on continuing to provide support and services to our tangata whaiora, their whānau and the wider community despite this setback.
"We are very thankful for the quick actions of staff on site who followed safety procedures keeping everybody safe, and further to the fire service for their very rapid response in containing the fire," Harding said.
"We have received a large outpouring of support from the community and
are extremely grateful for this."