Replace a rotten fence post

Dig out a rotten fence post safely, set a new one in concrete or a post support, and reattach your panels.

FP-01Check the fence and plan the jobLook at the whole fence line, not just the rotten post. If the post has snapped at ground level, check the panels either side are still sound enough to reattach. If this is a shared boundary fence, it is worth a quick word with your neighbour before you start, even though there is no legal requirement to ask permission for a like-for-like repair.

FP-02Gather your tools and materialsYou will need a spade, a post-hole borer or crowbar, a wheelbarrow, a spirit level, a pull saw or reciprocating saw, and something to brace the new post while it sets. Buy your replacement post, fixings and postcrete before you start digging, so you are not left with a hole and no way to fill it.

1 each · Pressure-treated timber post, 100x100x2400mm

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3 bag · Postcrete rapid-set concrete, 20kg bag

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1 pair · Disposable gloves

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FP-03Check for buried cables and pipes before you digGarden cables and water pipes can run in unexpected places, especially near a house, shed or outside tap. Use a cable and pipe detector to sweep the area, but do not rely on it completely near boundaries or old installations, as it can miss deep or unusual runs. Find your stopcock (usually under the kitchen sink) and check it turns before you dig, so you can shut off the water fast if you strike a pipe, and if you are digging near the house, turn off the relevant circuit at the consumer unit first if there is any doubt.

FP-04Remove the old postIf the post has rotted off at ground level, dig around the buried stump with a spade, breaking up any old concrete footing with a crowbar as you go. If a stump will not budge, cut it flush with a saw and dig out what remains rather than fighting it. Aim for a hole roughly 300mm across and 600mm deep for a standard fence post.

FP-05Clear and square up the holeRemove all loose soil, old concrete and rubble from the base of the hole so the new post sits on firm ground. Add 50mm of hardcore or rubble in the bottom for drainage, so the post is not standing in a puddle after rain. This single step is the main reason posts rot early, so do not skip it.

1 bucket · Hardcore or rubble

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FP-06Treat the new postEven pressure-treated timber benefits from an extra coat of end-grain preservative on any cut ends, since these are the weak point where rot starts. Paint the bottom 700mm of the post generously and let it dry before it goes in the ground. Do this before fitting, not after, as you cannot reach the buried section later.

1 tin · Wood preservative, end-grain treatment, 500ml

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FP-07Set the new postStand the post in the hole and pack in dry postcrete around it, following the instructions on the bag, then pour on water to trigger the set. As an alternative, especially if you want the post out of ground contact for good, use a bolt-down or drive-in metal post support fixed to a firm base or spiked into the ground, then bolt the timber post to it above soil level. A metal post support will not rot, but it needs solid, stone-free ground to drive into cleanly.

1 each · Metal post support/spike, 750mm (alternative to concrete)

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FP-08Plumb, brace and leave to cureCheck the post is upright on two faces with a spirit level, then screw a temporary timber brace from the post to a peg in the ground on each side to hold it still. Leave postcrete for at least an hour before removing braces, and avoid putting any load on the post for 24 hours to let it fully cure.

2 each · Scrap timber battens for bracing

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FP-09Reattach the fence panels or railsOnce the post is firm, refit the panel brackets or arris rail using galvanised screws or nails, checking the panel sits level before you fix it fully. If the old brackets are rusted or bent, replace them rather than reusing them, as a weak bracket will fail again quickly. Fit a gravel board along the bottom if you have one, to keep the panel itself out of contact with wet soil.

1 pair · Galvanised fence panel brackets, pair

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1 box · Galvanised screws, 50mm, box

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1 each · Gravel board, 1.83m (optional)

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FP-10Tidy up and finishBackfill any gaps around the base with soil and firm it down, sloping it slightly away from the post so water runs off. Sweep up offcuts and old timber, and bag the rotten wood and rubble for disposal, since treated timber should not be burnt. Give the whole post a final coat of fence stain once the postcrete has fully cured, usually after 24 to 48 hours.

1 tin · Fence stain or treatment

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1 each · Rubble/waste sack

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