The most likely place for a fence post to become damaged is at, or just below, ground level. At this point, the wood is almost permanently damp, causing it to rot. Once a post is rotten, it can give no support and the section of fence butting up to it tends to lean out of alignment.
Fixing fences
To repair the post you must cut off the affected part and attach a supporting spur. This involves temporarily supporting the fence and then digging a hole around the post about 60cm square and 30cm deep.
Saw off the rotten part of the post once it is completely exposed and bolt on the concrete spur - 15cm or 20cm coach bolts are suitable. The straight face of the spur should be against the post. When it is in position, use a spirit level to check it is upright.
Hardcore should then be packed around the bottom of the spur and the hole filled with a coarse concrete mix, finished at ground level with a slope to drain rainwater off.
An alternative method
Another method for a fence post, which is not exposed to strong winds, is the use of a metal spike. After the rotten part of the post has been cut off, the ground must be tightly packed back into place.
The metal spike is then driven hard into the ground, while gently holding the fence out of the way.
Then the post should be hammered into the spike's square cup and bolted in place.
