"The heat was phenomenal — it was scary s***," he said.
His house now has fire damage — the gutters have dropped off and the paint is blistered. Fire staff are to make sure there is no fire in the ceiling.
The old wooden building next door to him in Guyton St was once a dairy and has been totalled by the fire.
Mr Morgan and others were told to keep clear of its smoke, which was thick and brown.
It was occupied by an Asian man and his mother, neighbour Graham Rye said.
The occupants were taken to Whanganui Hospital with possible smoke inhalation, St John station manager Trudy Taylor said.
A female firefighter was also taken to hospital to be checked out.
Whanganui's four fire trucks went to the blaze, Senior Station Officer Craig Gardiner said. They were joined by Marton and Ratana trucks. Palmerston North and Bulls were standing by.
Breathing apparatus was needed, and Mr Gardiner expected crews to start rotating.
Fire and Emergency NZ staff would stay at the scene until they were sure all was safe. The cause would be investigated.