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Picture a new boundary fence on a clay plot outside Chelmsford: one winter of wet weather and the posts have already started to lean. If you’re a homeowner, small contractor or land agent in Essex, this guide helps you choose post depths and details that survive our soils and winds. In our experience the three biggest factors are soil type, exposure and fence height — and getting these wrong costs time and money.
Essex ranges from shrink–swell clay that grips then heaves, to free-draining gravel and exposed coastal plots with higher wind loading. For practical material choices and local tips see: https://essexconcreteandfencing.com/choosing-fence-materials-in-essex/ and our company blog at https://essexconcreteandfencing.com/blog/. At Essex Concrete and Fencing we focus on foundations that withstand local conditions, not quick fixes.
A straightforward rule we use on site is to embed one-third of the finished fence height and aim below about 450 mm to avoid shallow frost. Practical embeds for typical panels: for 1.2 m (4 ft) fences bury 450–600 mm in gravel and 500–600 mm in clay (use 600 mm where exposed). For 1.8 m (6 ft) fences plan 600–750 mm in gravel and 700–900 mm in clay; on exposed or coastal sites choose the deeper end.
Match post length to panel plus gravelboard. For example a 1.8 m panel with a 150 mm gravelboard needs roughly a 2.7 m post set around 750 mm deep. Check local height limits before you start: https://essexconcreteandfencing.com/2m-fence-height-regulations-in-the-uk/.
We dig 250–300 mm diameter holes for standard 100–125 mm posts and 300–350 mm for corners and gates. In clay, taper the hole and bell the base to resist frost lift and seasonal movement — a plain smooth cylinder won’t perform. Leave a 50–75 mm concrete collar above ground and dome it to shed water away from timber.
Set centres to actual panel widths (often 1.83 m / 6 ft). Dry-fit with concrete gravelboards (see product details at https://essexconcreteandfencing.com/product-category/concrete-gravelboards/) and confirm panel fit before you pour.
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Drainage is decisive. Add 100–150 mm of 20 mm shingle at the base of each hole. On clay, form a gravel “chimney” to the surface so water can escape rather than sit against timber. In gravelly ground compact backfill well to avoid lateral movement.
Where ground stays saturated, consider concrete slotted posts or post sleeves to keep timber clear and reduce rot: https://essexconcreteandfencing.com/product-category/concrete-slotted-posts/.
From site work we expect a 20 kg post-mix bag to yield roughly 13–14 litres. Typical hole volumes: 250 mm x 600 mm ≈ 30 L (2–3 bags); 250 x 750 ≈ 37 L (about 3 bags); 300 x 750 ≈ 53 L (about 4 bags); 300 x 900 ≈ 64 L (about 5 bags). For product options see https://essexconcreteandfencing.com/product-category/miscellaneous-products/post-mix/.
Add the correct water to the hole, pour in dry mix, tamp and check plumb both ways. Expect an initial set in 10–20 minutes; allow 24–48 hours before fitting panels and 48–72 hours before hanging gates, longer in cold or wet conditions.
Concrete posts give low maintenance and resist rot. Timber posts are easier to cut on site but demand good preservative treatment and drainage. Keep panels off the soil with gravelboards and maintain the domed concrete collar.
For windy plots pick stronger panels (closeboard with solid rails) and robust posts — we see light panels fail sooner than correctly specified timber or concrete systems. Compare lifetime cost, not just the initial price.
Corners and ends take higher loads. Use larger section posts and increase hole diameter to 300–350 mm and depth to 750–900 mm in clay. Bell the base and brace posts while the concrete cures.
Gate posts should be heavier (125×125 mm or 150×150 mm) and set deeper — often around 900 mm. Fit quality hinges and allow full cure before hanging to maintain alignment.
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Plan the line, confirm panel and gravelboard widths, scan for services and agree boundaries. Run a string line and mark centres before you dig.
Many fit panels immediately or underestimate soil movement. A common issue we see is using shallow, narrow holes — depth without sufficient width still allows posts to wobble under wind or impact.
If you’re installing a decorative, lightweight partition within a sheltered patio, heavy embeds and concrete collars may be unnecessary. For listed properties or sites with unusual groundworks consult a specialist engineer or local authority first.
Check planning and height rules before starting; some sites need consent. See https://essexconcreteandfencing.com/2m-fence-height-regulations-in-the-uk/ for guidance. Confirm boundaries with neighbours and locate underground services before you dig — a scanner or plans will save delays and liability.
Avoid shallow holes on taller fences and never skip the shingle base in clay. Don’t over-water Post Mix and keep timber clear of soil with gravelboards. Finally, don’t hang gates until the post concrete has gained sufficient strength.
For long life pair concrete slotted posts with concrete gravelboards and sturdy closeboard bays — this combination copes with Essex winds and wet winters. If you prefer timber, use treated posts, metal shoes where needed and good drainage.
Rub a sample between your fingers — clay will feel smooth and sticky and can be rolled into a ribbon; gravelly soil feels gritty and drains fast. Dig a 300 mm test hole and observe how quickly water leaves it.
In our experience concrete posts are more durable on exposed coastal plots because they resist rot and high winds; timber can work if properly treated and kept well drained.
Buy 10–15% extra post mix and shingle to allow for oversize or deeper holes and soft patches. It’s cheaper than a return trip to the merchant.
If your boundary is disputed, the ground has made-up layers, or you plan tall or long runs on exposed land, get a professional survey or contractor. Complex sites benefit from experience and proper guarantees.
