Spacing is where most boundary-wire installs quietly go wrong. Peg the wire too close to a wall and the mower bounces off it or refuses to approach. Peg it too far and you leave a shaggy border you end up trimming by hand every week, which rather defeats the point. The right distance is not a single magic number. It changes depending on whether the mower can safely overhang an edge, whether there is a drop or water on the other side, and how the wire is meant to loop around an island bed. Let me walk you through the clearances that actually work in a real yard.

Why Spacing Matters More Than It Looks

The boundary wire tells the mower where the lawn ends, but the mower does not stop with a wheel exactly on the wire. It reads the signal, drives a little past, then turns. Most models overshoot the wire by a few inches before pivoting. That overshoot is the whole reason spacing exists. Set the gap so the mower can cross the wire without hitting anything hard, dropping off a ledge, or landing in a flower bed. Manufacturers publish specific figures in the manual, and those numbers vary by model, so always check yours. The ranges below are typical starting points, not a substitute for your own instructions.

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Clearance From Walls, Fences, and Hard Edges

Against a solid vertical obstacle like a wall, fence, or the side of the house, the common guidance is to keep the wire roughly 12 to 14 inches, about 30 to 35 centimeters, away from the object. That gap gives the mower room to run parallel without scraping its shell. The trade-off is a strip of grass along the wall the mower cannot reach, so you finish that edge with a strimmer now and then. If the passage between two walls is very narrow, you tighten the spacing and let the mower run a single track down the middle instead of looping both sides.

Neat lawn edge meeting a flush patio where a robot mower can overhang

Flush Edges the Mower Can Overhang

Not every edge needs a wide buffer. Where the lawn meets a path or patio that sits level with the grass, the mower can safely hang its cutting deck slightly over the edge. In that case you run the wire much closer, often only 3 to 5 inches, roughly 8 to 12 centimeters, from the border. The blade sits inboard from the shell, so a little overhang trims right to the paving without the blade ever leaving the deck. This is the trick that gives robot-mown lawns their clean edge against a driveway, and it saves a lot of hand trimming.

Water Gets Extra Room: Never trust the minimum spacing near a pond or pool. The mower drives a few inches past the wire before it turns, and a wet edge offers no grip. Add extra clearance around any water feature and confirm the exact figure in your model manual before you commit a single peg.

Ponds, Drop-Offs, and Danger Zones

Water and ledges get the widest berth of anything in the yard. For a pond, pool, steep drop, or a wall you could tumble over, push the wire well back, often 16 inches or more, around 40 centimeters or greater, and confirm the figure in your manual. The mower's overshoot plus a wet or slippery edge is a recipe for a machine in the water. When in doubt, add a few extra inches here. A slightly wider uncut margin near a pond is a fine price for never fishing your mower out of it.

Typical Boundary Wire Clearances at a Glance

  • Solid wall or fence: about 12-14 inches (30-35 cm)
  • Flush path or patio the mower can overhang: 3-5 inches (8-12 cm)
  • Pond, pool, or steep drop: 16 inches or more (40 cm plus)
  • Flower bed or soft border: 12-14 inches, looped as an island
  • Tree ring or birdbath: island loop with the same bed buffer
  • Narrow passage between two walls: tighten and run a single track
  • Two parallel wire runs to an island: within about 1 cm of each other
  • Sharp corners: replace right angles with a gentle curve
  • Gravel or rough surface: extra buffer to keep the mower on grass
  • Slippery or sloped edges: add a few inches beyond the standard gap

You will find more on this in How to Connect a Robot Mower to WiFi and the App.

Islands, Beds, and Flower Borders

For an obstacle sitting inside the lawn, like a tree ring, a bed, or a birdbath, you loop the wire around it as an island. Run the wire out to the island, around it, and back along the same path with the two runs close together, often within a centimeter or so, per your manual. Keep the same 12 to 14 inch buffer around the bed itself so the mower does not chew the mulch or clip the plants. Solid, raised bed edges can sometimes skip the loop, since the mower simply bumps and turns, but soft borders almost always need one.

Grass edge beside a garden pond showing a wide safety buffer for wire

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Corners, Curves, and Adjusting After the First Run

Wire hates sharp corners. On tight inside turns, ease the wire into a gentle curve rather than a right angle, so the mower can follow it without cutting the corner and clipping whatever sits there. After you peg everything, do not bury it yet. Run the mower a full cycle and watch the trouble spots. If it kisses a wall or misses a strip, nudge the wire an inch or two and test again. Only once every edge behaves do you commit the pegs or bury the wire. That single test lap saves hours of rework.

Where this leaves you

Boundary wire spacing rewards a little patience up front. Wide buffers guard walls, water, and drop-offs, while a tight gap along a flush path buys you that crisp edge against the driveway. The exact inches shift by model, so treat the numbers here as a solid starting point and let your manual set the final figures. Peg loosely, run one full lap, and watch the mower do the honest testing for you. Adjust the two or three spots that misbehave, then commit. Get the spacing right once and the lawn edges itself for years with almost no help from you.

It helps to read this alongside Burying vs Pegging Robot Mower Boundary Wire.