The concrete spur is the industry way of securing a fencing system. It offers decades of use without the need for unnecessary and expensive complete replacement. Being future proof is another benefit to concrete spurs - If you ever wanted to replace a timber post for whatever reason, it can be cut at ground level, removed and new timber post bolted on to the plumb & level concrete spur.
The post can be installed either along side, or in front of your post to suit.
With little disruption, around 1 hour per post, your fence will be plumb, true and level and more solid than the original post.
All fence posts, treated or not will eventually rot at ground level or below. Leaving the rest of the post structurally sound and therefore not requiring the expense of a new post, or indeed complete fence.