Two rail, three rail or four rail: it sounds like a style choice, but it is really a question about what you are keeping in, what you are keeping out, and how much ground movement your boundary has to cope with. Get it wrong and you either pay for timber you did not need or spend the next two winters patching gaps. Here is how we work it out on jobs around Winchester and the surrounding villages.
The rail count follows the job, not the other way round. A boundary marker across an open paddock behaves very differently to a fence separating a pony from a lane, and the timber bill reflects that.
As a rough guide for what we install locally:
A standard three rail horse fence runs about 1.2m to 1.3m above ground, with the top rail near the post top, the bottom rail roughly 300mm to 400mm off the ground, and the middle rail splitting the difference. That bottom gap matters: too low and it rots out early and traps grass; too high and a foal rolls under it.
Four rail fencing at the same overall height means tighter gaps, typically 250mm to 300mm between rails, with the lowest rail around 200mm to 250mm from the ground. If you want a four rail fence, do not just add a rail to a three rail layout, reset the whole spacing or you end up with an awkward wide gap somewhere.
Post spacing is usually 1.8m centres, which suits standard 3.6m rails spanning two bays and staggering the joints. On heavier clay or sloping ground we sometimes tighten to 1.6m.
Once spacing is fixed, the maths is straightforward. Divide your run length by the post spacing to get the number of bays, add one for the final post, then multiply bays by rail count. A 60m three rail fence at 1.8m centres is roughly 34 bays, 35 posts, and about 100 rail lengths of 1.8m, or around 50 full 3.6m rails.
Order 5 to 10 percent over. You will lose lengths to cuts at corners, gateways and anywhere the ground dips. Corners and gate posts also want to be heavier stock, typically 150mm or 175mm round rather than the 100mm to 125mm line posts.
Winchester ground varies a lot over short distances. Free draining chalk on the downs holds a post well but is hard work to drive; the heavier clay pockets nearer the valley move with the seasons, and that movement shows up first at the bottom rail. On clay we usually raise that lowest rail slightly and take more care over post depth, typically a third of the post in the ground.
Timber grade matters more than rail count for how long the fence lasts. Look for UC4 pressure treated softwood for anything in ground contact. Cheap rails split at the nail and sag inside a few seasons, and replacing sagging rails costs more in labour than buying decent ones did in the first place.
If your boundary sits within a conservation area, borders a listed property, or forms part of a covenant on a newer estate, check before you build. Height and style restrictions do exist locally and they are far cheaper to check than to undo.
Supplied and installed, post and rail in this area tends to land somewhere in the region of £35 to £60 per metre, though that genuinely depends on rail count, timber spec, access for machinery, ground conditions and how much clearance work is needed first. A four rail fence is not simply a third dearer than a three rail: the extra fixings, the extra handling and the tighter tolerances all add up.
The honest advice is that most people do not need four rails. Unless you have small or young stock, three rails with netting where needed will serve you better and leave budget for better timber and deeper posts, which is where longevity actually comes from.
You can, but the spacing will rarely look right because the original rails were set for three. If you think you may need it, either build four rail now or plan to add stock netting instead, which is far less disruptive.
As a rule, around a third of the post length in the ground, so a 2.4m post for a 1.2m fence sits roughly 800mm deep. On soft or recently disturbed ground we go deeper, and gate and corner posts always go deeper still.
Usually not for line posts. Driven or well rammed posts in firm ground hold better long term than concreted ones, which can trap water. Gate posts and straining posts are the exception and are worth concreting properly.
Tell us about your fencing or gate job and we’ll get straight back to you with a clear, no-obligation quote.