Put up a fence post in concrete

Dig a hole, add drainage, set the post in quick-setting concrete, then keep it plumb while it cures.

FP-01Plan the job and check the rulesDecide how many posts you need and space them no more than 2.4m apart for timber fencing, or check your fence panel width. If you're replacing a boundary fence, it's good practice to tell your neighbour, even though there's no legal duty to unless it's a shared party structure. Fences over 1m high next to a road, or over 2m high elsewhere, usually need planning permission.

RULES

KNOW THE RULES

Under the Town and Country Planning (General Permitted Development) Order, fences over 1m near a highway or over 2m elsewhere generally need planning permission. Check with your local council before you dig if you're near this height.

FP-02Locate underground services before you digCables and pipes can run anywhere in a garden, not just in obvious lines. Use a cable and pipe locator if you have one, and check with your water and electricity suppliers for plans if you're digging somewhere new. Hand-dig the first 300mm with a spade rather than a mechanical auger, and treat anything you find as live or pressurised until you've proven otherwise. Know where your stopcock is (usually under the kitchen sink) so you can shut the water off fast if you nick a pipe.

1 each · Cable and pipe locator (hire, per day)

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FP-03Gather your tools and materialsYou'll need a post hole borer or a long-handled spade, a spirit level, a lump hammer, scrap timber for bracing, and enough postmix concrete for each hole. Buy timber posts already pressure-treated for ground contact, and check they're long enough to sit at least 600mm below ground.

1 each · Pressure-treated timber post 100x100x2400mm

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1 each · Post hole borer or spade

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4 each · Scrap timber battens (for bracing)

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FP-04Mark the position and dig the holeMark each post position with a stake or spray paint. Dig a hole about 300mm across and 600mm deep for a standard 1.8m fence post — roughly a third of the post's above-ground height should be buried. Keep the sides as straight as you can.

FP-05Add a drainage layerTip about 100mm of hardcore or rubble into the bottom of the hole and tamp it down. This stops the post base sitting in trapped water, which rots timber over time.

1 each · Hardcore/rubble, 25kg bag

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FP-06Stand the post and check it's plumbLower the post into the hole and hold it upright. Check it's vertical on two adjacent faces with your spirit level, then brace it with two scrap timber battens screwed to the post and pegged into the ground at right angles to each other. Get this right now — it's much harder to fix once the concrete goes off.

6 each · Wood screws 40mm

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FP-07Mix and pour the postmix concretePour dry postmix straight into the hole around the post, following the pack instructions for depth (usually two 20kg bags per post). Add the stated amount of water and let it soak in — most postmix doesn't need mixing by hand. Tamp gently with a stick to knock out air pockets, then shape the top so it slopes away from the post to shed rainwater.

2 each · Quick-setting postmix concrete, 20kg bag

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FP-08Recheck plumb while the concrete setsFast-setting postmix can start going firm within 10-15 minutes, so recheck the post with your spirit level straight after pouring and nudge it square if needed. Don't touch it again once it starts to stiffen.

FP-09Leave it to cure and remove the bracesLeave the braces in place for at least 24 hours, longer in cold weather — curing slows a lot below 5°C. Once the concrete feels solid and doesn't move when you push the post, remove the battens.

FP-10Tidy upScrape off any excess concrete from around the base while it's still workable, and backfill any gaps with soil. Bag up leftover rubble and packaging, and clean your tools before the postmix hardens on them.

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