9 Step Limestone Garden Path Edging with Marshalls Setts Over a 12-Metre Run

Costs Before the Trench Opens

Marshalls setts in the granite and limestone ranges usually sit between £1.50 and £3.50 each, with size and finish pushing the price up or down. A 12-metre edge laid on the short face puts the stone bill in the £120 to £200 range. Add a bulk bag of sharp sand, two or three bags of cement, and a length of timber for the string line, and the materials total stays comfortably below £300, assuming the wheelbarrow is already in the shed.

A standard sett is about 100mm across the face. If the pieces touch, 12 metres takes 120 setts. With a 10mm joint, the cleaner choice for an intentional path edge, the count comes down to roughly 110. Turn the setts so the 100mm depth runs along the line and the number halves again. That choice has to be made before digging, because the orientation changes the buried depth and the width of the trench.

Trench Depth, Fall, and Compaction

Cut the trench 150mm deep and about 200mm wide along the marked line. That gives enough room for a 75mm concrete bed, the buried part of the sett, and a small layer of bedding mortar above the concrete. Go shallower and frost heave can start lifting the run by the second February.

Set a string line between two pegs and check the fall with a spirit level. A garden path wants a slight gradient away from the house, close to 1 in 80, so water sheds off the surface and does not sit against the limestone. Across 12 metres, that gradient drops the far end about 150mm below the start. On the ground, the fall reads as a slow, steady slope across the length.

Compact the base of the trench before any concrete goes in. A hand tamper is ideal over this distance, though the flat end of a fence post will do the same job if it is used methodically. Loose spoil below the concrete is the common cause of uneven sinking, and it often shows months later as one sett sitting proud of the next.

Bedding the Setts and Building the Haunch

Mix the concrete bed at about 6 parts ballast to 1 part cement. It should be wet enough to hold a shape, with no soupiness. Shovel a 75mm layer into the trench and screed it roughly level with a trowel. The bedding mortar above it takes up small variations, so the concrete does not need a millimetre-perfect surface.

Lay the first sett at the high end on a 25mm dab of 4:1 sharp sand and cement mortar. Tap it down with a rubber mallet until the top face just reaches the string line. Check it across the width with a torpedo level.

Butter the trailing edge with a thin smear of mortar and place the next sett against it. Keep the chosen joint gap consistent; a 10mm timber spacer makes that easier over a long run. Every fifth or sixth sett, step back far enough to sight down the line and correct drift while the mortar is still workable.

After about a metre is in place, pack concrete behind the setts to form the haunch. This buried wedge is what keeps the edge from tipping outward under the load of the path build or the knock from a wheelbarrow. Shape it so it slopes down and away from the visible face, leaving space for soil or gravel to cover it later.

Leave the work untouched for 48 hours before pointing the joints or backfilling. Foot traffic too early presses movement into the green mortar, and those marks show as small twists and height changes along the run.

A concrete bed alone leaves the setts exposed to sideways pressure from the path. Without the haunch behind them, the line can look firm at first and still bow by the following spring as the edge takes repeated load from the adjoining build-up.

Limestone needs careful pointing because it is more porous than granite. A wet, sloppy mortar can stain the face and leave a grey bloom that brushing will not fully remove. Use a drier mix, press it into the joints with a pointing iron, and brush away loose crumbs once the mortar has firmed up but before it cures hard.

Cutting at Corners and Steps

A straight 12-metre run rarely needs a cut sett. Corners and step junctions are different: an angle grinder with a diamond blade cuts limestone cleanly in under a minute per cut.

Use eye protection, cut dry, work outdoors, and keep the dust away from open windows.

Planting Beside the Limestone Edge

The stone line is only part of the finished view. If the edge runs past box or yew, the planting has to be clipped tight enough that it does not flop over the setts and blur the crisp edge you have just built.

Niwaki sell Okatsune shears, the orange-handled Japanese shears often used for topiary. They hold an edge through a season of shaping in a way that supermarket shears do not. The 200mm blade pattern suits hand-clipping a low hedge beside a path because it trims cleanly without crushing the stems.

Box and yew planted within 150mm of a freshly haunched edge will push roots against the concrete over a few years. On a ground-level 12-metre path edge that is usually harmless, because the haunch is robust. If the same stone were retaining a raised bed, a root barrier would be the safer detail. For a simple path, plant 200mm back from the setts and clip the growth forward, letting the topiary soften the view while the roots stay off the concrete.

A clipped hedge also sheds fine debris, and limestone can hold organic staining. A 200mm strip of gravel or bare soil between the hedge base and the stone gives somewhere to rake clippings clear before they rot against the porous face.

Clay, Drainage, and the Deeper Build

Clay subsoil changes the build. Limestone setts on a concrete bed over shrinkable clay can move seasonally even with a good haunch, because the clay swells in winter and shrinks in a dry summer. Across 12 metres, visible humping and dishing can appear within a couple of years.

The fix is a deeper sub-base. Dig to 250mm instead of 150mm, lay 100mm of compacted MOT Type 1 hardcore, then place the concrete bed above it. The hardcore layer absorbs some clay movement and spreads the load, so the rigid concrete bed is separated from the worst of the ground movement. It means more digging and another bulk bag of aggregate, but on clay it is the difference between a path that holds its line and one that turns into a maintenance job.

Drainage makes the clay problem worse if it is ignored. Standing water in the trench swells the clay further and can interfere with the concrete curing. Where the ground stays wet, a 60mm land drain laid in pea shingle along the back of the trench, falling to a soakaway, takes water away from the bed. The stone is then being built on ground that behaves closer to a stable base.

Sandy or free-draining soil needs less structure. The 150mm trench and 75mm bed are normally enough, and the hardcore layer can often be left out. Before starting the main dig, a spade, a test hole, and a bucket of water will show how quickly the ground drains.

Rocking Setts After Frost

After the first hard frost, walk the length of the edge and look at the joints. Tight, even 10mm gaps that have stayed aligned show the bed and haunch are doing their job. Joints opened on one side, or setts that rock under a boot, point to a thin haunch or movement in the sub-base.

A run that looks identical from above can be carrying two different stories below the surface: compacted sandy ground under one edge, shrinkable clay and trapped water under another. The awkward part is how little of that difference is visible once the limestone faces have been pointed and brushed clean.