Things You'll Need
Flat pry bar
3 inch wood screws
Ledger board and sill plates are installed onto a foundation as part of a floor system of a building. The sill plate, usually a treated 2 by 8 board, rests flat on top of the foundation, and the ledger board, usually a 2 by 10 board, rests upright on top of the sill plate in an upright position. Rotted ledger boards or sill plates must be replaced to prevent structure failure. The average do-it-yourselfer can replace a rotted sill plate or ledger board in 6 to 12 hours, depending on the size and scope of the project.
Expose the ledger board of your building by removing any siding covering the bottom of the wall where the wood meets the foundation. Pry wooden siding away with a flat pry bar, taking care not to damage the siding. Chip away brick or stucco using a hammer, exposing only the area that is rotted.
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Cut away the rotted ledger board using a reciprocating saw. Stop just inside of framing floor joist. For example, if the rot along the ledger board is 8 inches long, then remove a 16-inch section that extends to a solid framing floor joist. Be careful not to cut into the sill plate beneath the ledger board when removing the ledger board.
Cut two 24 by 2 by 10 inch pieces of wood and scab them onto the floor joist on each side of the removed ledger. Align the two scabs with the ends of the floor joists, attaching them with 3 inch screws.
Cut a ledger board to the length of the removed rotted section, placing the new section into the removed section, and attach the new ledger patch to the scabs using 3 inch screws.
Remove the rotted sill plate using a reciprocating saw. Do not remove the ledger board that rests on top of the sill plate unless the ledger is rotted as well.
Cut out a length of treated 2 by 8 lumber from a new board that corresponds to the length of the removed rotted section. Measure the opening with a tape measure, cutting the new section 1/8 inch shorter to allow for expansion.
Gently tap the new sill patch into the opening between the ledger and foundation. Attach the sill patch to the ledger board by angling 3 inch wood screws through the ledger and into the sill plate patch.