How to Fix a Rotten Garden Fence Post
Last updated: 30 September 2026
Dig out the old post, install a new post in concrete, and refix the fence panels.
Overview
A rotten fence post is a common problem that can cause the whole fence to fail. This guide covers replacing a rotten post.
Step-by-Step Fix
Before beginning any repair, ensure you have isolated power or water supplies. Clear your workspace, gather standard hand tools, and wear appropriate personal protective equipment (PPE).
- First check the extent of the rot. Push the post to see if it moves. If the post is rotted at the base but sound above you may be able to use a post repair spike rather than replacing the whole post.
- If the post is rotted through and must be replaced remove the fence panels around the post. Use a pry bar to carefully detach the panels from the post. Set the panels aside where they will not be damaged.
- Dig around the base of the old post to expose the concrete footing. Use a spade or post hole digger. Break up the concrete with a sledgehammer or crowbar. Remove the old post and concrete from the hole.
- Dig the hole deeper and wider if needed to accommodate the new post. The hole should be at least sixty centimetres deep and thirty centimetres wide. This provides a solid foundation for the new post.
- Cut the new post to the correct height. Use pressure treated timber to prevent rot. Apply wood preservative to the bottom of the post and any cut ends for extra protection.
- Place the new post in the hole and check that it is vertical using a spirit level. Brace the post with timber or stakes to hold it upright. Mix postcrete or concrete according to the instructions.
- Pour the concrete into the hole around the post. Use a stick to tamp it down and remove air pockets. Mound the concrete slightly above ground level so water drains away from the post. Allow it to cure for at least twenty four hours.
- Once the concrete is set reattach the fence panels to the new post. Use galvanised brackets or screws. Check that the panels are level and secure.
- Apply wood preservative to the new post above ground level. This provides additional protection against rot. Allow it to dry before exposing to rain.
- To prevent future rot check fence posts annually. Look for soft spots or movement. Apply preservative every two to three years. Ensure the post is not in direct contact with wet soil.
Common Symptoms & Diagnostic Resolutions
Review the common error codes and operating symptoms below to quickly identify the root cause of the fault before ordering replacement parts.
| Symptom / Code | Likely Root Cause | Recommended Resolution |
|---|---|---|
| Post moves when pushed | Post rotted at the base | Replace the post or use a post repair spike if the rot is limited to the base. |
| Post is soft to the touch | Wood rot has spread through the post | The post must be replaced. Do not attempt to repair a rotted post. |
| Fence panels sagging | Posts no longer supporting the panels | Replace the damaged post and reattach the panels securely. |
| Post breaks at ground level | Advanced rot from ground contact | Replace the post. Use pressure treated timber and set it in concrete. |
Frequently Asked Questions
How do I know if a fence post is rotten?
Push the post to see if it moves. Look for soft spots or crumbling wood at the base. If the post moves or feels soft it is rotted and needs replacing.
Can I repair a rotten fence post without replacing it?
If the rot is only at the base you can use a post repair spike. This involves cutting off the rotted section and driving a metal spike into the ground to hold the post. For extensive rot the post must be replaced.
How deep should a fence post be set?
A fence post should be set at least sixty centimetres deep or one third of the post length. This provides stability and prevents the post from being blown over by wind.
How do I prevent fence posts from rotting?
Use pressure treated timber. Apply wood preservative to the post especially at the base. Set the post in concrete so it does not sit in wet soil. Ensure water drains away from the post.