How to Replace a Fence Post – DIY Guide
To replace a fence post, excavate around the old post, remove it along with any old concrete, set the new post in a freshly dug hole at least 600mm deep, pack with postcrete or concrete, allow it to set, then refix the fence panels.
- Spade
- Post hole digger or auger
- Spirit level
- Lump hammer
- Crowbar or post puller
- Tape measure
- Temporary props or stakes
- Mixing bucket
- Pressure-treated timber fence post (100mm x 100mm)
- Post mix concrete or ready-mixed postcrete
- Gravel or hardcore (for base drainage)
- Post cap or end grain sealer
- Fence panel clips or brackets
- Galvanised screws or nails
- Timber preservative
- Fence panel (if damaged)
Step-by-Step Guide
Assess the Post and Remove the Fence Panels
Before digging anything, detach the fence panels on either side of the failed post. Support the panels against the ground or prop them against adjacent posts so they are not under stress while you work. Check neighbouring posts at the same time — if one post has rotted, others may be close behind. This is also a good moment to check whether the panels themselves are worth reusing or need replacing. You can find more on general fencing repairs in our Garden Guide.
Excavate Around the Old Post
Dig around the base of the old post to expose the footing. Use a spade to cut into the soil in a circle roughly 300mm out from the post, then work down to a depth of at least 500mm. If the original post was set in concrete, use a crowbar to break the concrete away from the sides of the post. A post puller or a length of timber used as a lever can help work the post free without excessive digging. Take your time here — forcing a post out while the concrete is still gripping it can disturb surrounding ground and destabilise adjacent posts. If you have a leaning fence post nearby, address it at the same time.
Prepare the New Hole
The hole for the new post should be at least 600mm deep for a standard 1.8m fence, and 750–900mm deep for anything taller. A post hole digger or a hired petrol auger makes short work of clay or compacted soil. Pour a 50mm layer of gravel or hardcore into the base of the hole before the post goes in — this allows water to drain away from the end grain rather than pooling, which is the primary cause of premature rot. The hole diameter should be roughly three times the post width.
Set and Brace the New Post
Lower the new pressure-treated post into the hole and use temporary timber props to hold it perfectly upright. Check for plumb on two adjacent faces using a spirit level before fixing the props. Double-check the height against the posts on either side — fence posts in a run must all be at the same height if you want panels to sit level. Getting this right before pouring concrete is critical; once the post mix sets you cannot adjust it. Apply a coat of timber preservative or end grain sealer to the cut base of the post before it goes into the ground. For more on building a garden fence from scratch, our full guide covers post spacing and heights in detail.
Pour and Cure the Concrete
Follow the post mix instructions — most fast-setting mixes require you to pour the dry mix directly into the hole around the post, then add water. Tamp the mix down with a stick to eliminate air pockets and ensure it reaches all sides of the post. Slope the top of the concrete slightly away from the post to shed rainwater. Leave the props in place for the full curing time specified on the packaging — typically a minimum of four hours before light load, and 24 hours before reattaching fence panels. Do not be tempted to rush this step.
Refix the Fence Panels and Finish
Once the concrete has fully cured, reattach the fence panels using galvanised brackets, clips, or screws. Galvanised fixings are essential outdoors — standard steel screws will rust and stain the timber within a single season. Fit a post cap to the top of the new post to prevent rainwater sitting on the end grain. If you are treating and preserving the fence at the same time, now is the ideal moment to apply preservative to all exposed timber surfaces while the panels are still accessible from both sides.
Frequently Asked Questions
How deep should a fence post be set in the ground?
As a general rule, one third of the total post length should be below ground. For a 1.8m fence using 2.4m posts, that means burying at least 600mm. Taller fences need deeper footings — aim for 750–900mm for a 2.1m fence.
Can I replace a fence post without removing the fence panels?
It is possible on a gravel board system where panels sit in channels, but in most cases you will need to detach the panels to work safely around the post and ensure the new post is set perfectly plumb before the concrete cures.
Do I need to check with my neighbour before replacing a fence post?
If the fence is on a shared boundary, or if your title deeds indicate the fence belongs to your neighbour, you should discuss the work with them first. The ownership of boundary features should be indicated on your property’s title deeds, available via the Land Registry at gov.uk.
What size post do I need for a standard 1.8m fence panel?
For standard 1.8m fence panels, use 100mm x 100mm posts in a total length of 2.4m — this gives you 600mm below ground and 1.8m above. For heavier close-board fencing or exposed coastal sites, go up to 125mm x 125mm for extra rigidity.
How long does post mix concrete take to set?
Most fast-setting post mix products achieve working strength within four hours and full cure within 24 hours, though this can extend in cold or wet weather. Always check the manufacturer’s guidance on the bag and avoid loading the post before it has fully cured. If you are planning a larger project, our guide on how to fix a garden fence panel covers complementary repairs you can carry out at the same time.
When setting a post in post mix, hold a timber offcut against the side of the post and strike it with a lump hammer a few times after pouring — the vibration consolidates the mix around the post far better than tamping with a stick and eliminates voids that would otherwise weaken the footing.
Sources
- HSE — Safe use of hand tools and equipment — hse.gov.uk
- RHS — Garden boundaries: fences, walls and hedges — rhs.org.uk
- GOV.UK — Land Registry: property boundaries and ownership — gov.uk
This guide is for general information only. Always work safely and follow manufacturer instructions. DIYnut accepts no liability for injury or damage arising from DIY work.
