> Rafter tails that present with extensive rot often can be patched with two-part wood epoxy, but sometimes the damage is too extensive. A time-honored technique to safely restore them— without taking the roof off—is called a Dutchman repair. If the rafter ends are structural, temporarily brace the roofline with 4x10 or 4x12 lumber. Remove any paint around the damaged area. Then chisel or saw away the decayed wood. Use the same type of wood for the repair, and make sure it’s seasoned to avoid shrinkage.
Cut out a piece of wood—the Dutchman— that’s slightly larger than the area of damage. Lay the Dutchman over the damaged area and scribe an outline into the original wood surface below. Next, follow the scribed line with a chisel or small handsaw to form an opening in the existing wood for the new lumber. Apply a fungicide to the old wood and allow it to dry. Then glue the Dutchman in place with a waterproof adhesive, such as an epoxy formulated for wood. Trim or sand the surface of the patch until it’s flush to the surrounding surfaces. Prime and paint all exposed wood.
Damaged rafter ends are spliced with new wood, then planed or sanded smooth before finishing.