Concrete around a fence post does not rot, but the wood inside it does. After years in damp soil, your post softens at the ground line and gives way, while the concrete collar around its base stays where it was poured. When your old fence comes down, you still have those collars in your ground at every post position, on the same line you need for your new posts.
That leaves your replacement with two paths. New posts go in beside old concrete, or the old footings come out first so each new post starts in open ground. The day your fence goes up, you may not see which path your crew took. You will see it later, in your posts, your rails and your gate.
What Anchors an Old Post After the Wood Has Rotted?
A post set in concrete is held by the block around its base. The block bears against the soil on every side, and its weight and rough outer surface keep it from turning when wind pushes on the fence above. The post itself is only the handle on that block.
Wood fails first, and it fails at a predictable place. The few inches just above and below grade stay damp longer than the rest of the post, and they get air as well as water, which is the combination decay fungi need. Over the years, that band softens until the post breaks there or pulls loose, and the fence starts to lean or drops a section.
The concrete does not follow it. A footing poured around the post keeps its shape, its weight, and its grip on the soil long after the wood has gone soft, often with a length of the old post still locked inside. When the fence comes down, you are left with a buried block at every post position, each one exactly where the old line put it. Taking the fence down removes none of them.
Size varies as much as position. A footing takes whatever shape its hole had, so a block from a hole that caved in during the pour can be lumpy and wide, and one poured into a flared hole can be broader at the bottom than at the top.
Where the Old Footing Sits on the New Line
A replacement usually follows the run of the fence it replaces. The corners stay where they were, the gate stays in the same opening, and the posts between them fall at close to the same spacing, because rail lengths and panel widths were built around that spacing the first time. That puts each new post position on top of, or right against, an old footing.
Shift one post sideways to clear the old concrete, and two bays change at once: one gets longer and the other shorter. Rails cut to a standard length stop landing on the post centers, and pickets no longer break evenly at the ends of a bay. Shift several posts, and the line starts to wander, which you notice most when you sight down a straight run from one end.
Gate openings feel it first. The hinge post and the latch post are placed to a gate width, and a latch post nudged a few inches to dodge a footing leaves either a gap the latch cannot reach or a gate that binds. Corner posts take loads from two directions, and a corner that moves off its point pulls both runs with it. Each of those shifts traces back to one lump of concrete that nobody removed.
You may also find that the old footings do not sit quite where the old posts appeared to be. A post that leaned for years dragged the top of its collar with it, and a block poured off-center in its hole can reach toward the new line below the surface, well past what you see at grade.
What Anchors a New Post Crowded Against Old Concrete?
When a new hole is dug beside an old footing, one side of that hole is old concrete rather than soil. The new concrete poured into it does not fuse with the old block. It hardens against it with a seam between the two, so the side of the new footing that should be bearing on firm ground is bearing on a separate mass held only by the soil around it.
That matters because of how a post carries load. Wind on a solid fence and the swing of a gate push the top of the post; the post levers against its footing, and the footing pushes back against the soil on the far side. With a loose block on one side, the push goes into something that can rock or rotate. The two masses start moving as a pair, and a post that was plumb when you first saw it leans a little further after each hard push.
The new footing is also thinner where it meets the old one. A hole squeezed against existing concrete cannot be dug to its full width on that side, so the concrete wraps the new post unevenly, with a heavy wall on one side and a narrow one on the other. The thin side is the first to crack, and you rarely see it, because it happens below grade.
A second shortcut drops the new post into the old hole itself, with the old concrete broken at the top or partly left in place. The post then stands on a shelf of old concrete, shallower than the hole it replaced, in a footing that is a mix of old pieces and new pour.
Crowding reduces the new post's depth as well as its strength. A post squeezed in around old concrete often cannot be set to its full depth, and a fence built that way ends up anchored no better than the old one, still sitting on the same kind of posts-and-footings trouble that made you replace your fence in the first place.
Why the Dig-Out Belongs to the Replacement
Most fences that come due for replacement are failing from the ground up. Once a wood fence reaches that point, patching a panel rarely fixes it, because the trouble is in the posts and footings underneath. A replacement that leaves those footings in place carries part of the failure forward into your new fence.
So a complete replacement is one job: pulling the old fence, digging out the old footings, hauling everything away and building the new fence on clean ground. Dig-out is the step a cut-rate replacement skips to save on digging, and it is the step you can see least once the new fence is standing. When you compare estimates, it is fair to ask plainly whether every old footing comes out, and to have the reply written on the estimate you keep.
The work itself belongs to the crew. Old footings are heavy, awkward, and often larger than they appear from the surface, and breaking one loose requires equipment and a plan for where the pieces go. It is also digging, which brings a second hazard to this job, one that can kill outright.
Striking a buried gas, electric or cable line while digging out an old footing can kill, and lines may run only inches down, so leave every footing for the fence crew, who digs only after lines are marked.
An old fence carries no record of what was buried near it later. Cable, gas and electric lines can be added long after a fence goes in, and a line routed along a fence years afterward can pass close to an old footing without anyone in the house remembering it is there.
What a Clean Hole Gives the New Footing
With the old block out, the new post goes back on its original point, and the bay on each side keeps the spacing the rails were cut for. The hole around it is soil on every side, so the new concrete bears on firm ground all the way around rather than on a seam.
The footing also comes out whole. Concrete poured into an open hole fills it evenly, so the post sits centered in a full wall of concrete with no thin side waiting to crack. Gate posts stand plumb and stay there, and that keeps a latch lined up with its strike for years.
Spacing holds for the same reason. Because every post lands on its original point, rails cut to the old bay length fit the new bays, and a gate hangs in the opening it was measured for instead of one that drifted a few inches while the posts dodged old concrete. You notice this most at the ends of a run, where a crowded line tends to finish with one short, oddly cut bay.
Water behaves better around it too. Water reaching a footing in open soil soaks away in every direction, while a seam between old and new concrete can hold water against the post at grade, in the same band where your last post rotted.
A fence built on its own footings also starts its service life from zero. Nothing below grade is older than the posts you see above it.
Where the New Post Line Starts
Every new fence starts from the ground under its posts. On a replacement, that ground is either open soil at each old post position or a set of buried blocks the last fence left behind, and the choice between them is made before a single new post goes in. If you walk the run with your estimator, walk it one post position at a time and ask what comes out of each hole. You want to hear the old concrete, every time, so your new line starts where the first one did: in firm, open ground, with nothing older than the fence itself beneath it.
Frequently Asked Questions
Does the old concrete leave with the rest of the fence?
It should. On a full replacement, the broken-out footings are hauled away with the posts, rails, and pickets. If you see a bid that lists pulling the old fence but mentions nothing about the concrete, ask where your footings end up before you sign.
Do chain link and aluminum posts leave footings too?
Usually, yes. Chain link line posts and aluminum posts are commonly set in concrete too, and a steel post rusted through at grade leaves its collar behind just as a rotted wood post does. If you are switching materials, your new spacing may differ, so some old footings land mid-bay while others still sit right where your new posts go.
Can a new post go back in the exact spot once the footing is out?
Keeping each post on its original point is the reason to take the footing out. The hole is usually wider than the original, since the block comes out with soil around it. Your crew fills and firms that space while setting the post, so you get a footing sized for your post.
Will you see where the footings came out?
For a while. Each old post position leaves a patch of turned soil, wider than a post hole, and your grass takes time to fill in. If you have beds planted tight to the fence, expect disturbance there, since your crew needs room at every post to work the old block loose.
What should the estimate spell out about old footings?
Whether every old footing comes out, or only the ones in the way. Some replacements remove the blocks at gates and corners and leave the line-post footings in place. If your estimate lists footing removal, ask whether it covers every post position so you know where your new fence will stand.
What else can come up with an old post besides a solid collar?
A few things, and each changes the dig. Some collars come up hollow because the post rotted out inside, leaving a concrete cup that held water against the wood for years. Some posts were never set in concrete, only in tamped soil or gravel, and they lift out with no block. And your yard may hold two footings at one position, where an earlier repair set a post beside old concrete. Your crew finds out which at the first pull, and you may hear about it then.
Replacing an old fence with the footings dug out — every new post goes into open ground on the old layout, and buried lines are marked before the crew digs a single post hole. Crusberg Fence serves Yorktown and the Virginia Peninsula. Call (757) 508-0538.
