I recently moved into a basement flat that was converted about 2 years ago, the building itself is over 100 years old, and some of the walls in the flat are the orginal walls.  Recently I flooded my kitchen, over the last 2 months, brown marks have appeared on the wall in the kitchen and the walll between the kitchen and the hall...  I have been told to leave it to dry out which I am doing, however at the bottom of the hall wall that is damaged, I removed an old phone cable, and where the nails holding the cable go into the wall, the holes have appeared black, and the area around it about a cm, has become rather flakey....  Is there anything I can do to fix this or is the best thing to leave the wall to dry out completely.  Any advice would be appreciated.