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.
Determine the extent of the rotted wood, which will look shriveled and feel soft to the touch. If the damage is extensive and on a structural beam, you will have to replace the entire beam. On a decorative piece, you can just repair the damage no matter how extensive.
Cut out the soft, rotted wood with a sharp knife. Scrape away at the wood, which should come out easily, until you hit the hard, healthy wood.
Brush a wood hardener onto the remaining wood surface. This product will seep into the wood and prevent further rot.
Prepare a wood filler by kneading it until it is a consistent texture. Directions on the packaging will help you with this preparation process. Push it into the void left from the rotted wood as soon as you can. Allow the filler to cure for as long as the packaging suggests.
Place the finishing touches on the filler. It can be treated just as the wood around it. Sand it to smooth it out and blend it into the surrounding surface. Paint and carve it however you wish to match the surrounding wood.