Fire crews extinguished the blaze which ripped through the detached house in Dunmow Road, Takeley, after being called at 2.43am on Sunday.
Essex Fire Service said they managed to save horses at a nearby stable, reportedly with the help of neighbours, who described waking to a “sea of orange”.
It will carry out an investigation into how the fire started and then spread to the building, which has been left uninhabitable due to the damage.
Station manager Terry Maher said: “The owners were alerted to the fire by their dogs barking in the early hours of this morning.
“The fire started in an outbuilding at the rear of the property and quickly spread to the roof of the house.
“Crews worked incredibly hard, particularly due to the limited water supply, and did a fantastic job in saving the property and horses who were in a nearby stable.”
The road remained closed while work at the scene continued, with a diversion in place.
A neighbour told BBC News they woke to find the couple, who live in the house, in the garden with their two Chihuahuas.
Another spoke of helping crews lead three horses from nearby stables.
They said: “It was absolutely terrifying – the stables had filled with smoke, the horses were terrified and we had to lead them through blowing smoke and blowing embers.
“They were really good in the circumstances, but they were obviously traumatised by what was going on as there were blue lights everywhere, there was the fire and it was dark.
“You’re on autopilot then afterwards the shock hits you, but you can’t leave a horse to die of smoke inhalation.”