50% Off Delivery On Orders Over £750
Kent - Tel 01322-787312
London - Tel 020-8698-4064
How Deep to Dig Post Holes | What Size Posts Do I Need for My Fence?
Get your post depth wrong, and the rest of your fence is fighting a losing battle. Here is everything you need to know before you dig.How Deep Should a Fence Post Hole Be?
The standard recommendation you will see from most suppliers is 600mm (roughly 2ft). That is a safe, sensible default for most domestic fences, and if you are unsure about your ground conditions or want to keep things simple, stick with it.
But applied as a blanket rule across every fence height, it is not the full picture. The more honest guide is the one-third rule: your post should be buried to at least one-third of its total length. For lower fences in decent, well-draining ground, that will bring you in under 600mm. For taller fences, exposed sites, or soft and clay-heavy ground, you should meet or exceed it.
Here is a practical breakdown by fence height:
| Panel Height | Practical Minimum (Good Ground) | Conservative / Exposed Site |
| 3ft (0.9m) | 450mm | 600mm |
| 4ft (1.2m) | 500mm | 600mm |
| 5ft (1.5m) | 550mm | 600mm |
| 6ft (1.8m) | 600mm | 750mm |
| 7ft (2.1m) | 750mm | 900mm |
Top Tip: If your site is exposed, on a slope, near the coast, or the ground is soft or clay-heavy, always go deeper than the minimum. Ground movement in clay soils can shift posts that would hold perfectly well in firmer ground.
Hole Width
The hole width should be roughly three times the width of the post, regardless of depth. For a standard 75mm (3-inch) post, that means around 225mm wide. The concrete around the post is doing the holding work, not the soil, so getting the width right matters just as much as the depth.
For anything above 2.1m, use heavy-duty posts and go at least 900mm deep. Wind loading increases significantly with height, and standard posts are not built for it.
Browse our full range of wooden fence posts, including 3x3, 4x4, and slotted options to find the right match for your panels.
What Size Posts Do I Need for My Fence?
The calculation is straightforward: post length = fence height above ground + gravel board height + burial depth.
For a standard 6ft (1.83m) panel with a 150mm gravel board, your fence sits at roughly 1.98m above ground. Add 600mm for burial, and you need a post of at least 2.4m. Most people make the mistake of buying posts the same height as their panels. That leaves nothing in the ground, and the fence will not last a winter.
Here is a quick reference for common fence heights using a standard 150mm gravel board:
| Panel Height | Height Above Ground (inc gravel board) | Recommended Post Length | Minimum Hole Depth |
| 3ft (0.9m) | 1.05m | 1.5m | 450mm |
| 4ft (1.2m) | 1.35m | 1.8m | 500mm |
| 5ft (1.5m) | 1.65m | 2.1m | 550mm |
| 6ft (1.8m) | 1.98m | 2.4m | 600mm |
| 7ft (2.1m) | 2.29m | 2.7m | 600mm+ |
Wooden Posts or Concrete Posts?
Both work. The choice depends on your setup and how long you want the fence to last without intervention.
Timber posts are easier to handle, easier to cut on site, and look great with a wooden panel fence. The catch is that the base of a timber post, sitting in damp soil surrounded by concrete, is exactly the environment that rots wood fastest. Treated posts help significantly, but even pressure-treated timber will eventually rot at the base. Expect 15 to 25 years with a quality-treated post set correctly.
Concrete posts last far longer and require virtually no maintenance. They are heavier and more awkward to work with, but if you want a fence that outlives the panels themselves, concrete is the smarter long-term choice. They also work well in very wet or clay-heavy ground where timber deteriorates fastest.
If your existing timber posts have rotted at the base but the timber above ground is still sound, you do not have to dig them out. Concrete repair spurs bolt to the undamaged section of the old post and gives you a new concrete foot to set in the ground. It is a much cheaper and quicker fix than a full replacement.
What to Set Posts in
Never just backfill with soil. Posts set in loose earth will lean within a season.
Post-mix concrete is the standard choice. Pour it dry into the hole around the post, add water, and it sets hard in a matter of hours. Always place a layer of at least 50mm of gravel or ballast at the base of the hole before you drop the post in. This allows water to drain away from the very bottom of the post rather than pooling there, which is where rot starts.
Angle the top of your concrete mix slightly away from the post once set, so rainwater sheds away rather than sitting against the wood.
We stock post mix and cement in fast-setting options that are ideal for DIY installation.
Before You Dig: Check for Underground Services
This is not optional. Before any digging, contact your utility provider or use a service like Dial Before You Dig to locate any underground cables, pipes, or gas lines. It takes ten minutes and could save you from a very expensive or dangerous mistake.
A post hole digger (sometimes called a rabbit hole digger) is worth every penny for this job. It creates a clean, narrow, deep hole that a spade simply cannot match, and the post will sit far more securely as a result. You will also need:
- Tape measure and level
- Hammer and stakes (for marking your fence line)
- Mixing bucket or wheelbarrow for post mix
- Hand trowel for finishing around the base
A Note on Fence Panels
Getting your posts right is half the job. The other half is choosing panels that are actually built to last. Cheap panels cup, warp, and blow out within a few years. Our closeboard fence panels are among the strongest available and are designed to hold up to UK weather without the warping you get from overlap or waney panels.
Summary
- Standard post hole depth: 600mm for most fences up to 6ft
- Rule of thumb: bury at least one-third of the total post length
- Post length = fence height above ground + burial depth + gravel board height
- Always set on a gravel base and use post mix concrete
- Check for underground services before digging
- Choose concrete posts for longevity, timber for ease
The standard depth is 600mm, though the one-third rule is a more reliable guide: bury at least one-third of the total post length. The hole width should be roughly three times the diameter of the post, so around 225mm for a standard 75mm (3-inch) post. For fence heights above 6ft, increase depth to at least 750mm.
There is no fixed formula because ground conditions vary, but the maths is simple: post length = fence height above ground + gravel board height + burial depth. A 6ft panel with a 150mm gravel board sits at roughly 1.98m above ground. Add 600mm burial depth, and you need a post of at least 2.4m. In soft or exposed ground, increase the burial depth and size the post accordingly.
You need a post of at least 2.4m. This gives you 600mm in the ground, space for the gravel board and panel, and enough post above the panel for the slot overhang. In soft or exposed ground, go to a 2.7m post and 750mm depth. Never use a post the same height as the fence panel; it will not have enough in the ground to stay stable.
Slotted concrete posts have grooves running down both sides. Fit the gravel board into the slots first, then lower the panel in from above. Always set all your posts and let the concrete fully cure before fitting panels. Trying to fit panels while posts are still green can knock them out of position. Leave a small gap at either side of the panel in the slot to allow for expansion.
Most fencing contractors will dig post holes as part of a full installation, but few offer it as a standalone service. Your best option is to hire a petrol-powered post hole borer from a local tool hire company, which makes it straightforward for a competent DIYer and is significantly cheaper than bringing in a contractor.
Tape measure and level
A post hole digger, sometimes called a rabbit hole digger or clamshell digger, is the best hand tool for the job. It drives straight down and pulls soil up cleanly, keeping the hole narrow and vertical. For harder ground or a large number of holes, a petrol-powered auger from a tool hire shop is the practical choice. A standard spade produces holes that are too wide, too shallow, and difficult to keep vertical.
Chat With Our Team - We’re real people who actually enjoy talking about fencing (yes, really). If you need recommendations, installation tips, or help with an order, then reach out, and we will help.
Delivery Options - We offer fast, reliable delivery straight to your door. We use our own fleet of trucks to ensure your product gets to you in perfect condition.
Visit us - Based in Northfleet, Kent and Catford in London, we’re ideally placed for deliveries across London, Kent, Essex and beyond.
Call Us
• Kent - 01322 787 312
• London - 0208 698 4064
Email us - Get in touch via our website contact form.
WhatsApp us - We are only a text message away.
-
A fence panel is only as good as what it's standing in. Get the post wrong and it doesn't matter how good the panels are. DuraPost galvanised steel fence posts are built for anyone who wants a fencing system that stands the test of time. Whether you’re a homeowner replacing a tired garden fence or a contractor running out a commercial boundary, DuraPost provides a modern aesthetic that lasts.
-
Get your post depth wrong, and the rest of your fence is fighting a losing battle. Here is everything you need to know before you dig.
Mixing bucket or wheelbarrow for post mix
