Concrete posts and gravel boards in Margate, done to the coastal spec.

What's included

• Concrete slotted posts, 2.4m or 2.7m depending on final fence height
• Concrete gravel boards to close the base of the fence
• Post concrete mixed 4:2:1 ballast:sand:cement on site (not dry-thrown post-mix on load-bearing runs)
• Existing timber panels or boards retained and dropped back into the concrete channels
• Old timber posts extracted, holes back-filled

Timing

Retrofitting concrete posts and gravel boards to an existing 20-metre panel run: 2-3 working days including a next-day cure for the concrete before the run is loaded. The panels themselves take a couple of hours once the posts are set.

Margate-specific notes

Why concrete not timber posts on the CT9 coast. Timber posts fail at ground level - the point where the collar of soil holds year-round damp. On Thanet chalk-clay that damp does not drain, and even UC4-treated softwood posts get 8-12 years before rot at the base takes them out. Concrete posts do not rot. On a properly-set concrete post with a concrete gravel board keeping the timber off the ground, the timber above lasts twice as long because it is dry.

Retrofit vs new build. Retrofitting concrete posts to an existing panel run is a good economy at the half-life of the fence - when the posts are starting to rot but the panels have another 5-8 years in them. On a fence where the panels themselves are due, the smart move is a full closeboard or panel rebuild rather than saving the panels.

Chalk substrate depth. Palm Bay and clifftop Cliftonville substrates can hit chalk at 400mm. The post still needs 600-800mm of purchase for a 6ft-fence load, which means either drilling into the chalk (rare, mostly a hard pack over the top holds) or accepting a shorter effective post depth with a wider concrete collar.

Pricing

Concrete post and gravel board retrofit on an existing 6ft panel run: £45-65 per metre depending on ground conditions and how many posts. Concrete post and gravel board sub-structure as part of a full closeboard build is included in the closeboard per-metre pricing above.