Strathclyde Fire and Rescue Service teams wearing breathing apparatus fought the blaze inside the building, while crews tackled the fire from the outside using large main water jets.
No one was hurt but the cruise director, John Heald, said later that "the smoke was so intense and so thick that, even with breathing apparatus on, the teams could not get close to the source" of the fire.
Six firefighters wearing breathing apparatus tackled the detached garage blaze, which spread to houses on either side of the building, the fire service said.