Fence installation cost

Two rules govern how deep a fence post goes, and almost everything written about fencing mentions only the first.

The one-third rule is about leverage. A fence is a long lever with the wind pushing on it, and burying a third of the post gives it enough purchase in the soil to resist being pushed over. That is where “a six-foot fence needs an eight-foot post” comes from.

The frost line is about something else entirely. Water in the soil freezes and expands, and it lifts whatever is founded above it. Not evenly — one post rises more than its neighbour, and the fence between them goes out of true. The next winter it happens again. Within a few years a perfectly built fence is visibly leaning and nothing about the carpentry was wrong.

So the depth is the greater of the two, plus clearance so that the bottom of the hole sits properly beneath the freeze. In the south the one-third rule wins and posts are short. In the north frost wins by a wide margin, and it changes the post you have to buy as well as the hole you have to dig.

Posts go six to eight feet apart for wood and vinyl, and up to ten for chain link. Closer is stronger and costs more posts; wider sags, especially in wood, where an unsupported rail will bow within a couple of seasons.

The problem nobody warns about is what happens at the end of a run. Divide 47 feet by 8 and you get five full panels and a seven-foot remainder — fine. Divide 42 by 8 and you get five panels and a two-foot stub, which looks exactly like what it is: a mistake.

The fix is not to add a panel. It is to spread the spacing evenly across the whole run: six bays of seven feet instead of five of eight and one of two. Posts a few inches closer together are invisible, and one short panel is the first thing anyone notices.

A post hole takes more concrete than people expect, because it is a cylinder and volume grows with the square of the diameter. A ten-inch hole three feet deep is about 1.6 cubic feet before you subtract the post — close to three 60 lb bags, or about a bag and a half of the 80 lb size.

Multiply that by twenty posts and the concrete alone is a pallet. It is also why frost depth moves the budget twice: deeper holes are more digging and considerably more concrete.

The argument between them is real and neither side is silly. What is not negotiable is the depth: gravel set below the frost line outperforms concrete set above it, every time.

One detail worth doing either way — crown the top of the concrete so it sheds water away from the post rather than forming a collar that holds it. That single trowel movement adds years to a wooden post.

Three quarters of everything people search about fencing is price, so here is the shape of it — and the shape is that labour dominates.

Chain link is what the search volume in this category is really about, and it is the cheapest way to enclose a large area by a wide margin. Wood privacy is the default back yard and the one that needs maintaining. Vinyl costs half as much again up front and then asks for nothing. Aluminium is what pool codes and front boundaries get, and it outlasts the house.

The comparison almost everybody is actually making. Up front vinyl is dearer; divided by the years it lasts, it is not — and that is before the staining, which is the cost nobody puts in the sum because almost nobody keeps it up.

The honest case for wood is not economics, and pretending otherwise is how people end up disappointed. It is that wood can be any colour, can be repaired a board at a time, and does not read as plastic from three feet away.

And if the job is enclosing ground rather than screening it, neither is the answer — chain link is less than half of either and outlives treated wood.

Every per-foot price you will be quoted is for fence, not for gates, and the difference is not small. A gate is a lever hanging off a single post, swinging several times a day for twenty years.

That means heavier posts — a six-by-six where the fence uses four-by-fours — set deeper than the run, often with a diagonal brace or a tension cable in the leaf itself. It means hinges and a latch chosen to carry the weight rather than to match the price. And it means time spent hanging and adjusting so it still closes when the ground moves next spring.

Fences are the most disputed structure in residential building, and almost all of it comes from four questions that are cheap to answer beforehand and expensive afterwards.

Where is the line? From a survey — not from the old fence, the kerb, or where the grass changes. Fences built on assumption are the most common boundary dispute there is, and the remedy is to move them. If the pins cannot be found, a surveyor costs a fraction of relocating finished work.

What is buried there? Call the national dig line before any post hole. It is free, it is legally required in most places, and gas, power and fibre all run through yards at depths that a post hole reaches easily.

What do the rules allow? Height limits differ between front and back yards, setbacks are not always zero, and some jurisdictions specify which side the finished face must show. A homeowners’ association can add materials and colours on top of all that.

Have you told the neighbour? Not a legal requirement in most places, and the single best investment in the project. A fence on a shared line affects two houses, and the conversation is free before the posts go in and costly afterwards.

Post depth takes the greater of the one-third rule and the frost line plus 6 inches of clearance, and the panel says which of the two is driving it — because that is the interesting part. Frost depths are compiled design figures by state, given at the deeper end where a state spans a range, and the requirement that anything load-bearing be founded below the frost line comes from the model residential code. Prices split material from labour, since fencing is the trade where the split matters most. Everything is on the sources page, dated.

One assumption worth stating: runs do not share posts with each other. Where two runs meet you tell the calculator it is a corner, and it counts one post there rather than two — which is why the corner and end fields matter more than they look.

Nothing you type is sent anywhere — the whole calculation runs in your browser.

Line, corner and end posts are not interchangeable, and frost heave is the word for what happens when the depth is wrong.