Crews were called to the fire in an end-terrace basement in High Street, South Queensferry, at about 05:15.
Further back-up was requested, resulting in six fire engines and one command support unit being involved in the operation at its height.
No-one is thought to have been injured in the incident. A investigation into the cause is under way.
Fire crews used high pressure jets and breathing equipment to tackle the flames.
A Scottish Fire and Rescue Service spokeswoman said: "Two appliances from Crewe Toll were mobilised to the address.
"When crews arrived, a further two appliances were requested from South Queensferry and Dunfermline. Due to the severity of the fire, a further two appliances were requested from Dunfermline and Bathgate.
"This made a total of six appliances and one command support unit."
Some crews remained at the scene during Saturday morning, dampening down the area.
About 40 firefighters have been working to bring a severe house blaze under control.