I have an old house (about 150 years old) which has an issue with rising damp. Plastic sheets were placed under the floors, so they aren't affected, but the walls (up to a max of 4 foot) are damp because ultimately they sit on the earth, I suppose, and must soak up the water. I've treated some of the symptoms with anti-damp paint, but I have no idea how to deal with the cause.
Around the exterior of the property is concrete. On one side it is higher than the others (making one side of the property semi-basement). However, there is no obvious means for water to actually enter the property. It is possible that water seeps down from the garden. I also do not know if the drains/sewers have any cracks etc.
Does anyone know how any approaches for dealing with this problem, or at least mitigating its effects?