How to Repair Rotted or Damaged 4X4 Wood Posts

Written by michelle raphael
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The biggest problem with wooden outdoor structures is that they will eventually need some repair to fix damaged or rotted areas. Even weatherproofed cedar or redwood will show the trials of harsh winters followed by drastically hot summers. Fences and other outdoor structures are expensive to replace even if you built them yourself. Individual fence boards can be replaced easily, and the 4x4 posts that support the structure can be repaired if you do it as soon as the trouble spots become evident.

Skill level:

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Things you need

  • Marker
  • Saw
  • Yardstick
  • 1-by-4 cedar board
  • 2-by-4 cedar board
  • Plane
  • Wood glue
  • Drill
  • Screws
  • Cap for the post
  • Mender plate
  • Sledgehammer

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  1. 1

    Mark the areas on the posts that need to be repaired all the way around the post. Make sure that you draw the line evenly because if you do not, the cut will be crooked. Use a yardstick to ascertain the straightness.

  2. 2

    Cut off the rotted portions of the 4x4 posts with a saw.

  3. 3

    Mark and cut out a notched piece of the remaining post so that it matches the thickness of the 1-by-4 cedar, and glue the piece in the notch. Stand a 2-by-4 inch piece of cedar alongside the other piece. Cut the 2-by-4 piece so that it fits nicely on top of the post next to the 1-by-4. With that 2-by-4 in place, cut a second notch next to it on the side opposite the first notch, and put another section of 2-by-4 in it. Glue the pieces in place, then screw them together. The screws on the second 2-by-4 will have to be countersunk because that side will stick out a little must be planed down to match the rest of the post. The length of the boards you use depends on how high you need to make the repaired post.

  4. 4

    Allow the glue to dry for a day and put the cap on. Weatherproof the new wood and the cap. When the weatherproofing is dry, stain it or paint it to match the rest of the post.

  5. 5

    Look to see if any of the areas below the ground may need tending. If so, get metal stakes called mender plates that can be driven in with a sledgehammer. Hammer them down right next to the damaged area at least 4 feet. They come in pairs, so do one on either side of the post even if both sides are not damaged.

Tips and warnings

  • Checking your fences and other wooden structures seasonally will keep you on top of any problems before they get out of hand.

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