How to Repair Wood Siding

House wood siding


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There is nothing like real wood siding to beautify a home. With its elegant profile and low thermal conductivity, wood siding is a value-boosting addition to most homes. Like any organic building product, wood is subject to decomposition.

As long as the exterior paint is stable, wood clapboard siding can last for decades. But even a hairline crack in the paint can introduce water, and water leads to rot and mold. Though wood siding is very strong, a sufficient physical impact can split and crack it. Repairing wood siding is integral to owning a home with wood siding.

The most important step of any wood siding repair is the final process of weatherproofing the repair area with paint (or another type of sealant) and caulk. This essential for protecting not just the wood siding but also the building materials and structural elements behind the siding.

Tools and Materials

  • Utility knife and several replacement blades
  • Pry bar
  • Hammer
  • Electric miter saw
  • Speed Square
  • Carpenter's pencil
  • Multi-tool fitted with a wood blade
  • Safety glasses
  • Dust mask
  • Tape measure
  • Replacement wood or fiber-cement clapboard siding board
  • Stainless steel siding nails (1 3/4-inch long)
  • Exterior-grade caulking
  • Primer and exterior paint

Overview: Repairing a Single Wood Siding Board

Your damaged wood clapboard siding board will be firmly rooted in place. All wood clapboard siding is coated in paint, often multiple layers that have been applied over decades. Compounding that, caulking may have been injected into seams at any of the four edges.

Nails pierce both of top and bottom adjacent boards, plus the damaged board itself. These connections make your job trickier because you need to remove the damaged board without disturbing surrounding boards. After the damaged board has been removed, you will cut a new board to size and slip it into place.

Mark the Repair Area

In rare instances, you may want to remove the entire length of the siding board. But this is usually unnecessary since it is possible to excise just the damaged portion of a siding board while leaving the other portions of that same board intact.

Choose a section that extends about a foot past the damaged area. Place the Speed Square against the bottom of the damaged siding board and draw a vertical line with the carpenter's pencil. Do this on both sides of the damaged area.

Cut Away the Paint and Caulking

With your utility knife, slice away the paint and caulking that connects the damaged board to its neighbors. Push the knife all the way through to ensure that the connection is fully broken. You may need to make multiple cuts. Change blades frequently. Extend the cuts a few inches past your vertical pencil marks.

Make the Vertical Cuts

An electric multi-tool is the best tool for making this type of plunge cut. Since multi-tools are so versatile in home improvement work, it may be worth it to you to purchase one. Fit the wood blade onto the multi-tool. With your safety glasses and dust mask on, turn on the multi-tool and cut on the vertical lines. Be careful with your cuts, stopping as soon as you have completed cutting through the board.

Remove the Nails

Force the pry bar into the gaps between the damaged board and adjacent good boards. Gently rock the pry bar back and forth. This will cause the nail heads to protrude slightly enough so that you can pull them out with the claw section of your hammer. Remove the damaged section of siding.

Cut the New Siding

Use your damaged section of siding as a template for marking the dimensions on the new siding board. Cut the new section of siding to size on the electric miter saw.

Nail the Replacement Siding Board in Place

Slide the replacement siding board upward, underneath its top neighbor. Make sure that the board is flat against the side of the house. Nail the replacement siding board into place initially by driving nails through the existing holes in the top board.

Because these will not hold in the long-term, drive additional nails in other locations on the top board. Stay along the bottom half-inch edge of that top board so that you can be sure of piercing the replacement siding board.

Next, nail along the bottom of the replacement board. Be sure to remain on that bottom half-inch to make sure that the nails pierce through to the adjacent bottom board.

Caulk and Paint the Siding

Caulk all horizontal seams between the boards. For the vertical seams, inject caulk, then force the caulk farther into the seams by rubbing with your finger.

After the caulk has fully cured, prime the board and coat with an exterior paint of your choice. Since this is a new board, a minimum of two coats of paint is highly recommended.