Tongue and groove siding is a popular building material that protects the underlying structure from weather damage. Tongue and groove siding is an interlocking type of siding. Minor repairs to tongue and groove siding can be made by patching the defects with wood filler. More severe damage requires that the damaged board or section of board be cut out and removed, and then replaced with a new, intact piece of siding. The process of repairing tongue and groove siding is the same whether the siding is covering a house, shed or garage door.
Use a putty knife to apply exterior wood filler to minor cracks, holes or gouges in tongue and groove siding. Work the filler into holes, and smear some excess product over the top and edges of the defect being repaired.
Follow the manufacturer's instructions regarding dry time. Smaller repairs, like nail holes, require a few hours to dry, while wider, deeper-filled defects can require 24 hours or more to dry completely.
Sand the dried repair with 120-grit sandpaper. Work the filler smooth with the sandpaper and bring it flush to the surface of the surrounding siding.
Use a wood chisel and mallet to separate the damaged section of siding from the intact portion. Strike the chisel with your mallet to cut across the width of the board.
Use a circular saw to cut the damaged section of board in half lengthwise. Adjust the saw blade's depth so it matches the thickness of the siding material. Because tongue and groove siding locks together, you need to cut the board in half and then remove each half of the board individually.
Pry the bisected board away from the house to expose the nail shafts. Place the pry bar inside the cut you made with the circular saw.
Pull the nails with a slater's ripper, or cut them with a hacksaw blade saw. A slater's ripper is a specialised tool that you can slide underneath the siding to grab and pull the nails free. A hacksaw blade saw is a narrow-toothed saw blade mounted on a handle. Use the hacksaw blade saw to cut the exposed nail shafts.
Pull the freed sections of board from the garage door.
Use a circular saw to cut a replacement piece of tongue and groove siding to the proper length.
Cut the lower groove off of the bottom edge of the replacement board with a table saw. This will allow the board to fit into place between the siding boards above and below.
Fasten the board into place with corrosion-resistance nails. Follow the existing nail pattern to maintain a consistent finish.
If you are planning to stain the garage door, use a wood filler that matches the tone of the wood and can accept stain.