Getting the Post Length Right First Time
One of the most common questions we hear from customers is: "What length concrete post do I need for a 6ft fence?" It's a great question — and the answer depends on two things: how deep the post must be buried, and whether you're using a gravel board.
Getting this wrong means a fence that's either too short or unstable. This guide gives you the practical numbers so you can order with confidence.
The Two Things That Determine Post Length
1. Burial Depth
A concrete post still needs to go into the ground. The standard rule of thumb used across the UK fencing trade is to bury roughly one-third of the total post length — so for a post carrying a 6ft (1.83 m) fence panel, you typically need around [CONFIRM: 600 mm burial depth is a widely cited guideline — verify this suits your ground conditions and panel weight] of post below ground.
Please note: burial depth can vary depending on soil type, exposed location, wind loading, and local ground conditions. We recommend confirming the appropriate depth for your site before ordering.
2. Gravel Board Height
A gravel board sits between the base of the fence panel and the ground. It protects timber panels from rot and makes replacement simple. The two most common heights are 6 inch (150 mm) and 12 inch (305 mm).
Calculating Your Post Length
The total post length you need is roughly:
Fence panel height + Gravel board height + Burial depth
6ft Panel + 6-inch (150 mm) Gravel Board
- Panel height: 1,830 mm (6ft)
- Gravel board: 150 mm
- Burial depth: [PLACEHOLDER — confirm with your supplier or structural guidance, typically around 600 mm for standard residential conditions]
- Suggested post length: [PLACEHOLDER — typically around 2,400 mm / 8ft — confirm before ordering]
6ft Panel + 12-inch (305 mm) Gravel Board
- Panel height: 1,830 mm (6ft)
- Gravel board: 305 mm
- Burial depth: [PLACEHOLDER — confirm with your supplier or structural guidance, typically around 600 mm for standard residential conditions]
- Suggested post length: [PLACEHOLDER — typically around 2,750 mm / 9ft — confirm before ordering]
These figures are a practical starting point based on widely used UK trade guidelines. Always verify the correct post length for your specific site, soil conditions, and fence design before purchasing.
Exposed Post Height
It's worth checking your exposed post height too. Once installed, you want the post to finish level with — or just above — the top of the fence panel. Too much post showing above the panel looks untidy; too little and the panel isn't fully supported in the slot.
With a slotted concrete post, the panel and gravel board slot directly into the grooves, so the exposed length (above ground) should equal the panel height plus the gravel board height:
- 6ft panel + 6-inch gravel board = approx. 1,980 mm exposed
- 6ft panel + 12-inch gravel board = approx. 2,135 mm exposed
Our Concrete Posts and Gravel Boards
We stock a range of sizes to cover both configurations above. Our Concrete Slotted Posts are available in multiple lengths and are manufactured to accept standard UK fence panels and gravel boards in their moulded slots — no fixings required.
Pair them with our Concrete Gravel Boards for a low-maintenance base layer that resists ground moisture, won't rot, and won't need replacing when you eventually swap a fence panel.
Practical Tips Before You Order
- Check your ground: Soft, sandy, or waterlogged soil may require a greater burial depth than the standard guideline.
- Count your bays, not your panels: You need one more post than the number of panels (e.g. 3 panels = 4 posts).
- Allow for corner and end posts: These sometimes require a different profile — check with us if you're unsure.
- Planning considerations: Fences over a certain height, or those bordering a public highway, may require planning permission. Always confirm local planning requirements before installation.
- Mix and post: Concrete posts still need to be set in a concrete mix (postcrete or similar). Ensure the hole diameter is adequate for a secure set.
Still Not Sure? Get in Touch
If you're measuring an awkward run, working with an existing wall, or just want to double-check before you order, we're happy to help. Use the contact details on our website and tell us your panel height, gravel board choice, and the number of bays — we'll point you to the right products.
Disclaimer: The figures in this guide are based on widely referenced UK trade practice and are provided as a general starting point only. Roman Fencing Ltd does not provide structural engineering advice. Always confirm burial depths, post sizing, and any planning requirements with a qualified professional or your local authority where required.