The three Grade II-listed thatched houses at Silvergate caught fire late on Saturday afternoon.
Norfolk Fire and Rescue Service incident commander Simon Mason said crews may remain at the scene for a second night.
A National Trust spokeswoman thanked firefighters who "worked tirelessly".
Residents from two houses have gone to stay with family and friends, while the third family has been re-homed in a holiday cottage, the National Trust said.
"We do not know the cause or full extent of the fire yet but, most importantly, there have been no reports of any injuries and all of the tenants were able to get out of the cottages," said the trust's spokeswoman.
"We are enormously grateful to the crews who reached the cottages quickly, worked tirelessly to tackle the fire and have maintained a constant presence."
About 70 firefighters attended the blaze as it ripped through the roofs of the cottages.
"We expect to be on the scene for the remainder for the day and maybe over the night," said Mr Mason.
An investigation into the cause of the fire has been launched.
Three families lost their homes when fire engulfed a row of National Trust cottages on the Blickling estate in Norfolk.