If your house measures 14 meters from front to back then you will need 2 if your house measures 8 meters from front to back then you need one.
Basically you need one at every 6 meter interval. If you will be placing weight over a load bearing wall then you will also have to be certain that it is adequately supported all the way down to the foundation.
This means if there is a through lounge on the ground floor you will have to make sure the beam in that area is also suitable.
Best thing to do would be to get advice from a structural engineer on this matter.
