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Concrete posts vs timber posts on the Broadstairs coastal belt

There is a legitimate debate about concrete vs timber fence posts for inland plots. On the Broadstairs coastal belt there is not: concrete wins because timber posts fail too fast in salt air. Here is the straight-up comparison, and where each still makes sense in the town.

What each post is

A timber fence post is tanalised softwood (usually redwood pine), 100mm x 100mm cross-section, pointed at the base, set in a postcrete footing. A concrete slot post is a cast concrete post, same 100mm x 100mm cross-section, with mortice slots down two faces that accept fence panels or arris rails. Concrete is heavier, harder to handle, and does not rot.

Working life on the Broadstairs coastal belt

Timber posts within half a mile of the sea front last 8 to 12 years before rot fails them at ground level. Concrete posts on the same belt last 30+ years: the failure mode is spalling or cracking from freeze-thaw, not rot, and that is a decades-long process. On any run within sight of Viking Bay, Stone Bay, Kingsgate or North Foreland, concrete posts pay for themselves twice over.

Wind loading

The Kingsgate and North Foreland clifftops catch serious wind. A 6ft closeboard fence acts as a sail: the wind loading on a 15m run in a gale is measured in kilonewtons. Timber posts fatigue under repeated loading and the concrete footing eventually loosens. Concrete posts are stiff enough that the wind loading is transferred to the concrete footing without fatiguing the post itself. On any exposed clifftop run we do not offer timber posts as an option.

Inland Broadstairs

The story is different at Reading Street, St Peter's or Westwood. Sheltered from the coastal wind, less salt in the air, timber posts get 15 to 20 years of working life. The cost saving on timber posts (about £30 per post vs concrete) can be legitimate if the customer is looking at a 10 to 15 year horizon rather than a lifetime. We are happy to fit timber posts inland if that is what the customer wants.

Cost comparison over 25 years

Take a 15m run, five posts. Timber posts at £30 each = £150, replaced twice over 25 years (three total sets) = £450 in posts, plus three sets of labour to reset the run = probably £1200 total cost of ownership. Concrete posts at £60 each = £300 in posts, set once over 25 years = £600 total including one set of labour. Concrete comes out roughly half the cost over a proper working horizon.

Aesthetic considerations

Some customers do not like the look of concrete posts. That is a legitimate objection: a slot post has a visible edge line between the post and the panel that does not exist with a timber post. On cottage-style picket fencing at St Peter's, and on any front-garden fence where the post is visible from the highway, timber is often the right answer for the look. For rear-garden closeboard or panel where the post is not really visible, concrete wins on economics.

The retrofit answer

You do not have to replace the whole fence to move to concrete posts. If the existing panels or closeboard timber is still sound, we can strip out the failing timber posts, set concrete posts on the same line, drop the existing panels back in, and add gravel boards at the bottom. Retrofit costs 30 to 40% less than a full new fence and buys you the concrete-post working life.