Dry rot only occurs on wood containing moisture, despite its name. Fungi, enjoying the moist wood as a home, invade the timber causing it to rot. This can occur on any piece of wood, basically anywhere in the home. Fixing dry rot can seem like a daunting task, but even those unskilled in carpentry can handle most cases. Some initial investigating will reveal to you the extent of the problem and whether you can fix it yourself.
Figure out the source of moisture causing the dry rot and eliminate it. The usual culprits are clogged gutters, leaking pipes and roof problems. To close off the moisture source, you may have to call a professional plumber, roofer or carpenter if you do not possess skills in these areas. Allow the area to dry out completely.
Brush a wood hardener onto the remaining wood surface. This product will seep into the wood and prevent further rot.