Gravel Board Calculator — Boards, Clips & Materials

A gravel board is a horizontal board that sits between the ground and the bottom of your fence panels. It protects the panels from ground moisture and rot, and makes panel replacement easier since you can lift panels out without disturbing the posts. While not mandatory, gravel boards significantly extend fence panel life and are strongly recommended for any panel fence installation. Use our Fence Panel Calculator for a complete materials list including panels, posts and postcrete. Gravel boards are equally important under close board (featheredge) fencing — our close board fencing calculator works out how many fence slats per metre you need along with posts and arris rails.

Concrete gravel boards are the most popular choice in the UK. They are rot-proof, maintenance-free, and typically last 25+ years. They cost more upfront (around £6-10 each) but never need replacing. Timber gravel boards are cheaper (around £3-6 each) but will eventually rot even with pressure treatment, typically lasting 5-10 years before needing replacement.

It depends on the post profile. With slotted concrete posts (the most common system), the gravel board simply slides down into the post groove and is captive — no clips or cleats are needed. With mortice (feather-edge) concrete posts, the board is secured with galvanised 2-pin gravel board cleats, one at each end. To fix a concrete gravel board to a timber post you need a galvanised U-bracket at each end. A timber gravel board on timber posts is simply screwed or nailed direct to the inside face. So a standard slotted-post fence needs zero clips, while mortice posts and concrete-board-on-timber-post setups typically need two fixings per board.

Gravel boards should match the width of your fence panels. Standard UK gravel boards are 1.83m (6ft) long to match 6ft panels, or 1.52m (5ft) for 5ft panels. The standard height is 150mm (6 inches), though 300mm (12 inch) boards are available for sloping ground. Concrete gravel boards are typically 50mm thick.

Yes, gravel boards are particularly useful on sloping ground. On gentle slopes, standard 150mm boards can accommodate minor level changes. For steeper slopes, use taller 300mm gravel boards or stack two standard boards. The fence panels then sit level on top while the gravel boards handle the ground variation beneath.