Concrete Fence Posts: Specification Guide
Concrete posts remove the single most common failure point in a timber fence — rot at ground level — at the cost of a harder, less forgiving repair if the post itself is ever damaged.
Most fence failures we're called out to start at the post, not the panel, and specifically at the band where a timber post meets the soil. Concrete posts solve that failure mode outright, which is why we recommend them as the default upgrade on almost every quote — but they're not free of trade-offs, and this page sets those out honestly.
Checklist before you buy
- Confirm slotted vs morticed to match your fence type
- Check post size against fence height and exposure
- Confirm base depth in the written quote, not just 'concreted'
- Ask about gate post upgrades if the run includes a gate
- Discuss cladding/gravel board options if the concrete finish matters to you
Sizes and slot systems
Concrete posts come slotted (a groove down each face to drop gravel boards and panels straight in) or morticed for rail-and-board construction like closeboard. Slotted posts are the standard pairing for panel fencing; morticed posts suit closeboard and T&G builds.
Standard sizes are 100×100mm for domestic runs and 125×125mm or larger for taller fences, gate posts, or exposed boundaries carrying more wind load.
| Post type | Best for | Note |
|---|---|---|
| Slotted | Panel fencing, gravel boards | Panels drop straight in, fast to build |
| Morticed | Closeboard, T&G | Rails fixed into mortices, needs careful setting out |
| Corner/end | Run terminations | Different slot configuration to mid-run posts |
Base depth and setting
Concrete posts are set into a concrete base of their own — typically 600–750mm deep for a 1.8m fence, deeper again for gate posts or corner posts carrying extra load. Post spacing follows the same 1.8–2.7m centres as the panel or board type above it.
Honest pros and cons
Pros: no rot, no warping, decades of structural life, and a genuinely lower total cost of ownership than replacing timber posts every 10–15 years. Cons: a concrete post cracked by impact (a reversing car, a fallen branch) is harder and messier to replace than a timber post, and the finish is more industrial unless clad or painted.
- No rot at ground level — the single biggest cause of fence failure eliminated
- Structural life measured in decades, not years
- Harder to repair if impact-cracked, and removal disturbs more ground
- Visually more utilitarian unless timber-clad or gravel-boarded to hide the post face
Frequently asked
Are concrete posts worth the extra cost over timber?
In most gardens, yes — the extra up-front cost is usually recovered by not replacing rotted timber posts every 10–15 years, and panels can be swapped without disturbing the posts.
Can concrete posts be used with any fence panel?
Slotted concrete posts suit panel fencing directly; closeboard and T&G need morticed posts instead, which take rails rather than a panel edge.
What happens if a concrete post is damaged?
It usually needs breaking out and resetting, which disturbs more ground and neighbouring panels than a timber post swap — a genuine trade-off against their durability.
How deep should a concrete fence post be set?
600–750mm for a standard 1.8m garden fence, deeper for gate posts, corner posts or exposed elevated sites.
Do concrete posts look worse than timber?
They read as more utilitarian bare-faced, but gravel boards or timber cladding on the visible face largely hide this while keeping the structural benefit.