Fencing a Garden That Falls Away

The panels came off the wagon square and the garden did not

Twenty-six metres of boundary falling a shade over two metres from the corner of the house to the bottom gate, and the fence coming down was stepped. Three bays up from the bottom there is a wedge of daylight under the panel wide enough at the low end to put a boot through, and the client's terrier found it in March. What the quote has to settle, before a single post is priced, is whether the replacement steps like the old one or rakes with the ground. They are not two finishes of the same fence. They buy different post lengths, different bay widths, different quantities of everything below the bottom rail, and they fail in different places.

Everything on the wagon is square. Lap panels arrive as rectangles inside a framed border. Concrete posts are cast with their slots parallel. Even a bundle of featherboard comes cut to one length. The ground is the only unmanufactured part of the job, and fencing a fall is entirely the business of reconciling the two. There are exactly two ways to do it and no third: hold the infill level and drop it in steps, or let the infill follow the ground and rake it.

The consequence most estimates miss is that only one of those produces a hole. A raked fence keeps its bottom edge parallel to the ground the whole way, so there is nothing underneath to close and the wedge never exists. A stepped fence leaves a triangle under every bay, its height at the low corner equal to the step, and the gravel board is the only component allowed to fill it. That one fact drives most of what follows — the bay width, the post lengths, how many gravel boards come off the truck, and whether the ground gets dug at all. What the fall does not change is the argument about wind, soil and frost that sizes the hole in the first place; that is worked through in Setting a Fence That Stays Up and is no different on a bank. What is different is where you measure from, which is a much smaller point and costs considerably more money.

The infill decides this, and the estimator does not

Step or rake feels like a taste question and is mostly a materials question. Walk down the list of things you might actually hang and most of them can only do one of the two, so the decision is usually made the moment the client picks a fence out of a brochure — and it is worth making that explicit to them at the point they pick, not when the posts are already in.

A framed panel steps because the frame is the structure. Lap and overlap panels are thin slats stapled into a light border, and the border is what stops the whole thing folding into a parallelogram; recut it on a rake and nothing is holding the slats but the staples. Slotted concrete posts are the same argument in another material — the slot is cast square, cannot be recut, and the panel that drops into it has to be a rectangle. Rigid welded mesh has no give in it at all. Any of these on a fall is a stepped fence whether or not anybody chose one.

Closeboard on arris rails is the flexible one, because every board is fixed individually and the rails can sit at whatever angle the ground offers. That gives three options rather than two: rake it, step it, or the variant nobody mentions in the brochure — level top with a raked bottom, where the boards get progressively longer down the run. That last one is the answer when the fence has to line through with a wall coping, a garage eaves line or an existing run at the same height, and it is the most expensive of the three because no two boards are the same length.

Then there is what it looks like from the kitchen window. A stepped fence reads as a series of horizontals and sits well against a house, a terrace and formal planting. A raked fence reads as one continuous ribbon and suits an open or rural boundary. Neither is wrong, but mixing them is: if you are replacing one length of a boundary that continues past the plot, match what is already standing. A raked bay between two stepped neighbours is the single detail that looks like a mistake from every angle in the garden.

The wedge under the panel, and what is allowed to fill it

Put a level panel over falling ground and what is left underneath is a right-angled triangle the full width of the bay, open at both faces, with its height at the low corner exactly equal to the step. On a 1 in 8 with 1.83 metre bays that corner is 229 millimetres clear of the soil. It is not a gap in the sense of a shrinkage crack; it is a hole in the fence, and it is in every bay of the run rather than in one bad one.

The gravel board is the adjustment layer, and its height is the largest step you are able to accommodate. Which means the bay width comes out of the board rather than the other way round: the widest bay you can close is the board height divided by the grade.

A 150 millimetre timber board on a 1 in 8 gives 1.2 metre bays, which is a lot of extra posts. A 300 millimetre concrete board gives 2.4 metres, more than a panel is wide, so the panel width wins and the board has capacity to spare. Anywhere past about 1 in 5 with a standard panel there is nothing on the rack that closes it, and you are into two boards, narrower bays, or ground work.

Ground work means taking the soil out under the high end of each bay so the panel bottom meets it, which turns a smooth fall into a run of short level terraces under the fence line. It works and it is a barrow of spoil per bay, but it has a consequence worth naming: the component that ends up sitting in soil is a component that was not specified to sit in soil. A lap panel's bottom rail is not a ground-contact item. BS EN 335 sets the use classes for that in Europe and the AWPA Use Category System does the same job in North America, and a gravel board is the part that carries the ground-contact specification. So dig down to a gravel board, never to the panel.

Leaving the wedge open costs more than it looks. Mowers catch it, foxes and dogs use it — the wire answer to that lives in the smallholding guide rather than here — and it is the first thing photographed when a boundary is disputed. It also grows. Water runs along the underside of a fence on a bank because that is the lowest continuous line available to it, and it takes the fines with it, so the 100 millimetre gap at handover is a 160 millimetre gap after three winters and nobody did anything to cause it.

The height you are allowed, measured from ground that is not level

In England the permitted development limit for a fence, gate, wall or other means of enclosure sits in the Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 2, Class A: two metres in general, one metre where it adjoins a highway used by vehicular traffic, and an application above that. The Order expresses the limit as a height above ground level. It does not say which ground level, and on a bank there are two of them. Authorities publish their own reading and the higher side is the common one, but it is a question for the planning department before the posts are ordered rather than a question for a forum afterwards.

A stepped fence sharpens that question in a way a raked one does not, because a stepped fence has a tallest point and it is not where anybody looks. At every intermediate post the panel on the uphill side sits a full step above the ground on the downhill side of that post, so the fence measures panel plus gravel board plus step at that spot. A 1.8 metre panel over a 150 millimetre board is 1.95 metres on the flat and comfortably inside the limit; put the same components on a 1 in 8 with 1.83 metre bays and the low corner of every bay is 2.18 metres above the ground beside it. Raked, the identical fence never exceeds 1.95 metres anywhere on the run.

That same arithmetic is the post schedule. Every post but the lowest wants to be one length up: timber can be bought long and cut once the panels are hung, and a slotted concrete post cannot be cut at all, so it goes up a standard size and the extra goes into the ground — which on a bank is no bad place for it.

Cut ends, ground contact and a finish that has to survive a bank

Raking multiplies field cuts. A stepped run is factory ends and one saw cut at the odd bay; a fully raked run is two cuts on every board on the job. Every one of them goes straight through the treated envelope into timber that was never treated, and the standards are explicit that the person making the cut owns the remedy: AWPA M4, Standard for the Care of Preservative-Treated Wood Products, and BS 8417, Preservation of wood — Code of practice, both put field cuts and borings into the same category. Do it on the bench with the boards flat and the ends up, before anything is fixed. Brushing preservative onto a cut end already sitting 40 millimetres above a gravel board is a job everybody claims to have done and nobody has done properly.

Which end matters depends on the method, and both answers are the same failure. On a raked board the low end is nearest the soil and is the last place water leaves, so that is the cut that decides how long the board lasts. On a stepped run it is the panel's bottom rail at the high end of each bay — the part that ends up buried when somebody digs the ground out to close the wedge. In each case a component with a use class printed on its label has been put somewhere the label did not cover, which is what the use class systems exist to stop.

The finish itself is mostly the coatings guide's territory: coverage rates, how much more a rough-sawn face drinks than a planed one, and whether both sides are being done are all settled there and there is no point restating them. What the fall adds is area that a length-times-height rectangle does not see. A stepped run shows a step of bare post face at every post, carries two gravel boards where the flat stretch carried one, and if it is raked has a run length that is the longer of your two figures rather than the shorter. Total the bays individually where it matters, or feed the plan length against the tallest section height and treat the answer as a floor rather than as the number.