high levels of humility

[paul161201]

I recently moved into a Victorian house which has high levels of humidity The humidity levels are higher at the back of the house usually about 80%. I never dry cloths within the house and use extractor fans in the kitchen i bathroom.
The bottom of walls in the kitchen and hallway become damp but when i use a dehumidifier the walls dry out. here are a few pictures of damp patches within my house the damp patch on the wall is about a meter from the ground

 

[John D v2.0]

I'd the humidity is higher inside than out, check under the floor boards for sources of moisture.

 

[paul161201]

The humidity is usually higher inside the house then outside
The downstairs floor has been filled so no floorboards. if their was a leak under the floor upstairs would it be be noticeable with a damp patch on the ceiling?

 

[^woody^]

How you use the heating and ventilation is the direct cause of high humidity levels.

 

[paul161201]

At the moment i am using a dehumidifier in the kitchen which brings humidity down to 50% within 2 hours of turning off the dehumidifier its back up to 80% humidity.
I notice the kitchen floor tiles are a semi gloss type which make them look wet. Are they the breathable tiles that are laid on damp floors?
is it worth digging a french drain along the kitchen wall? photo of outside of kitchen wall below their is only about 2 inch in height between the kitchen floor and the ground outside