More than 50 firefighters have been tackling a blaze at the Grade II listed house in Hurst.
Fire broke out at about 6.45am in one part of the Tudor building, with 10 crews from Berkshire called to the scene.
A family of four including two young children were evacuated safely, along with a maid.
Three ambulances were called to the scene as a precaution. A fire investigation officer is on scene to determine the cause of the blaze, which is not thought to be suspicious.