Choosing a concrete post starts with one important question: does “6ft fence” mean a 6ft-high panel, or a finished fence that measures 6ft including the gravel board? Those two projects need different calculations.
This guide explains the sizing arithmetic. The burial depths below are illustrative placeholders for Roman Fencing to approve, not installation specifications or guarantees of suitability.
We recommend posts be to be atleast 2ft “600mm” in the ground to insure a long lasting fence. Especially at 6-7ft total fence height.
The simple sizing calculation
Post length = required post height above finished ground level + approved burial depth.
For an arrangement where the gravel board sits entirely above ground and the post finishes level with the panel top, the exposed height is the panel height plus the gravel board height. Any post projection above the panel must also be added. Confirm the actual panel and board dimensions, slot length and intended ground levels before ordering.
A 6ft panel with a 6-inch gravel board
A nominal 6ft panel on a fully exposed 6-inch board gives a nominal finished height of 6ft 6in. An 8ft post would leave only 1ft 6in below ground if its top were flush with the panel. Do not assume that burial depth is suitable.
A 9ft post would leave 2ft 6in below ground at that same exposed height. It is therefore a length to discuss with your installer, rather than an automatic answer.
A 6ft panel with a 12-inch gravel board
A nominal 6ft panel on a fully exposed 12-inch board gives a nominal finished height of 7ft. A 9ft post would leave 2ft below ground with the post top level with the panel. An 8ft post would leave only 1ft below ground and must not be selected simply because the panel is 6ft high.
If 6ft means the total finished fence height
To keep the total nominal height at 6ft, a fully exposed 6-inch gravel board leaves 5ft 6in for the panel above it. A fully exposed 12-inch board leaves 5ft for the panel. Check available panel sizes and actual dimensions rather than assuming a panel can be shortened.
With exactly 6ft of post above ground, an 8ft post leaves 2ft below ground. This illustrates the calculation only; the burial depth still needs approval for the site and installation.
Check the site before choosing the post
Measure from the intended finished ground level. Slopes, stepped panels and differing ground levels on each side can change the exposed post requirement. If part of a gravel board sits below ground, calculate its exposed height separately; do not treat it as a retaining structure without suitable professional advice.
Ask your installer to confirm ground conditions, wind exposure, the installation method, footing dimensions, burial depth and any underground services before digging. Check local planning requirements for your proposed finished height and location before starting work. This guide does not establish planning permission or structural suitability.
Choose your posts and gravel boards
Browse our Concrete Slotted Posts, including 8ft and 9ft options, and our Concrete Gravel Boards in nominal 6-inch (150mm) and 12-inch (300mm) heights.
Nominal imperial and metric labels are not exact conversions. Confirm actual component measurements and compatibility before placing your order. When asking us about sizing, include your panel height, gravel board height, intended finished height and any slope or changes in ground level.