Kumara Volunteer Fire Brigade deputy fire chief Les Neame said the two men were lucky to get out with their lives.
After waking to a house full of smoke they only escaped by crawling along the floor in acrid darkness.
One of the men was able to get to his daughter's house and use her phone to alert the Fire Service about 3am, which delayed the alarm being raised by half an hour.
The scene of the blaze was about 2km east of Dillmanstown and a couple of kilometres down a 4WD-only bush track — which could not be accessed by the fire appliance.
A light 4WD equipped with a pump was instead sent from Greymouth, but Mr Neame said there was "absolutely nothing we could do".
The dwelling, a basic bach measuring about 10 square metres, was not fitted with smoke alarms.
"They were very, very lucky to get out — they were minutes away from not being in this world.
"All they had were shoes and the clothes they were wearing."
The men lost their phones in the fire and, having to go elsewhere to call services, added to the delay in help.
The fire is believed to have started by a potbelly stove. It is now being investigated.
Greymouth fire crews were turned back when it became apparent there was nothing to be done.
"There was nothing to put out — it was just a smouldering mess," Mr Neame said.
- Meg Fulford