The phrase “robot vacuum” implies a thorough job. In practice, the most common complaint about robot vacuums after a few months of ownership is the dust strip along the baseboards that the robot never seems to reach. A round robot leaves a 2 to 4 cm strip of uncleaned floor against every wall, and that strip accumulates dust until a manual edge clean is performed. This guide walks through why edge cleaning is hard for round robots, which designs address it, and which models actually reach the wall.
The geometry problem
A circular robot vacuum with a 35 cm diameter rolls along a wall with one point of contact at any moment. The main brush bar is mounted inside the circle, typically 15 to 20 cm from the front edge and 8 to 12 cm from the side edge. The bristle or rubber roller cannot reach material outside its own width.
The result: a strip 2 to 4 cm wide along every wall is outside the brush bar’s path. Dust accumulating in that strip is the dust the robot leaves behind.
This is the most basic limitation of round robot vacuum design and it cannot be solved by suction or by software alone. Either the brush has to extend outside the body, the body itself has to be non-round, or a side brush has to flick debris into the brush path.
D-shape designs: the older solution
Neato (now defunct) and Roomba’s s9 line used a D-shape. The flat front side of the robot pressed against the wall along a 20 to 25 cm line. The brush bar sat directly behind this flat edge, putting the brush in contact with the wall-edge band.
In tests, the s9 left a dust strip of 0.5 to 1 cm against walls, compared to 2 to 4 cm for round Roombas. The improvement was meaningful.
The cost of the D-shape is a larger footprint (the flat front cannot fit through narrower gaps), more complex navigation (the robot must align itself to enter rooms front-first), and slightly higher manufacturing cost.
iRobot discontinued the s9 line in 2024. Neato shut down in 2023. As of 2026, no major brand sells a current D-shape robot. Used and clearance s9 units still appear on Amazon at $400 to $600.
For a buyer who prioritizes edge cleaning above all else, a used s9 remains the best option. For buyers who want a current model with warranty, the s9 is not available.
Side brushes: the standard solution
Every round robot uses one or two side brushes that extend outside the robot body. Three or five bristle arms (or a flexible silicone arm) sweep at 100 to 200 RPM and flick debris from the edge band toward the main brush path.
Side brushes work for loose debris (crumbs, hair, larger particles). They do not work well for fine dust pressed into the floor-wall junction. The flick motion lifts loose material; it does not scrub.
A typical side brush reduces the missed edge band from 4 cm to 2 cm in tests. Useful, but not solving the problem.
Worn or partly-bent side brushes reduce edge cleaning meaningfully. Replacing side brushes every 3 to 6 months recovers most of the edge performance.
Extending side brushes: the 2024 to 2026 innovation
The Roborock S8 MaxV Ultra introduced an extending side brush in 2024. The brush is mounted on a small arm that extends 8 to 10 cm beyond the robot body when LiDAR detects a wall within 5 cm. The extended brush sweeps a wider arc and reaches further into the edge band.
Dreame followed with a similar mechanism on the X40 Ultra. Roborock’s 2025 Saros 10R refined the design further with a faster extension speed and a stronger spring return.
In tests on the S8 MaxV Ultra, the extending side brush reduces the missed edge band from 2 cm to less than 1 cm in most rooms. The improvement is the most significant edge-cleaning advance since the D-shape.
The cost is added mechanical complexity (more parts to wear), slightly higher manufacturing cost, and a premium of $300 to $500 over the same robot without the extending mechanism. For users who care about edge cleaning, the premium is worth it.
Extending mop pads
A few flagship 2025 to 2026 models also include an extending mop pad: a rotating circular pad on a small arm that swings out toward the baseboard when the robot detects a wall. The Roborock Saros 10R and Dreame X40 Ultra both ship this feature.
Effective reach: 8 to 10 cm beyond the robot body, similar to the extending side brush. The pad mops the wall-edge band the way the extending side brush sweeps it.
The last 1 to 2 cm directly against the baseboard still goes untouched because the pad cannot physically extend that far without contacting the wall and dragging dirty water against it.
For mop edge performance, the extending pad is the best solution currently available. Without it, manual edge mopping is required every 4 to 8 weeks.
Software: edge mode
Most current robots offer an edge-cleaning mode in the app. The robot follows the perimeter of each room deliberately at the start or end of the clean. Suction is set to maximum, side brushes run faster, and the robot moves slower along the walls.
The improvement is measurable: 15 to 25 percent better edge pickup compared to a standard mode that crosses the room first.
Edge mode is most useful on robots without extending hardware. For users with older flagship robots (Roborock S7 MaxV Ultra, Roomba Combo j7+), scheduling an edge run once a week is the best way to improve edge cleaning without hardware changes.
Corners: the deeper problem
Corners (90-degree wall junctions) are the worst spot for any round robot. The brush bar cannot reach inside the corner; the side brush flicks debris partway out but does not get into the corner itself; even D-shape robots leave a small triangular gap.
The honest assessment: every robot leaves a 3 to 5 cm triangle in every corner uncleaned. Extending side brushes reduce the triangle but do not eliminate it. Manual corner cleaning (with a small handheld vacuum or a vacuum attachment) is required every 2 to 6 weeks depending on dust load.
For a buyer who wants completely clean corners, no robot solves the problem. The robot reduces frequency of corner cleaning but does not eliminate it.
Models ranked for edge cleaning in 2026
- Roborock Saros 10R ($1,800): extending side brush, extending mop pad, fast LiDAR wall detection. Best edge cleaner currently sold.
- Roborock S8 MaxV Ultra ($1,600): extending side brush, fixed mop. Strong second place.
- Dreame X40 Ultra ($1,500): extending side brush and extending mop. Roughly tied with S8 MaxV Ultra.
- Roborock S8 Pro Ultra ($1,300): five-arm side brush, no extension. Good but not class-leading.
- Roomba Combo 10 Max ($1,400): five-arm side brush, no extension. Similar to S8 Pro Ultra.
- Mid-tier round robots (Roborock Q Revo, Roomba j7+): standard side brushes, no extension. Adequate but leave visible edge strips.
For broader robot vacuum methodology, see our /methodology page.
The honest framing: edge cleaning is a hardware problem that is finally being addressed in 2024 to 2026. For buyers who care about clean baseboards, the extending side brush models are the first robots that actually solve the problem at the wall. For everyone else, a manual edge pass once every 4 to 8 weeks remains part of robot vacuum ownership.
Frequently asked questions
Which robot vacuums clean edges best in 2026?+
The Roborock S8 MaxV Ultra and Saros 10R lead on edge cleaning thanks to extending side brushes and extending mop pads that physically reach out toward the baseboard. The Neato D-series ended in 2023 but a D-shape design still has the largest contact patch against the wall. The Roomba s9 (discontinued but still on shelves) was the last D-shape Roomba. For currently available models, the Roborock S8 MaxV Ultra is the best edge cleaner, followed by the Dreame X40 Ultra.
Why do round robots miss the edges?+
Geometry. A circular robot rolls along the wall with only one point of contact at any moment. The brushes are inside the circle, not at its edge, so debris in the 2 to 4 cm closest to the baseboard never enters the brush path unless the side brush flicks it inward. The flick-inward mechanic works for loose debris but not for fine dust pressed into the floor-wall junction. D-shape robots have a flat side that contacts the wall along a 20 to 25 cm line, which lets the brush bar reach material the circular design misses.
Do extending side brushes really help?+
Yes, measurably. Tests on the Roborock S8 MaxV Ultra and Saros 10R show 30 to 50 percent better dust pickup in the wall-edge band compared to a fixed side brush on the same robot platform. The extending mechanism deploys when LiDAR detects a wall within 5 cm, reaches out 8 to 10 cm beyond the robot body, and sweeps a wider arc. The mechanism adds cost and adds a wear point but the cleaning improvement is real.
Can I improve edge cleaning on a robot I already own?+
Partially. Replacing worn side brushes (every 3 to 6 months) restores edge sweep effectiveness. Setting the robot's app to run an edge-cleaning mode (most apps offer this) makes the robot follow walls deliberately rather than crossing the room first. Adjusting the suction to maximum on edge passes helps. None of these matches the hardware advantage of an extending side brush, but they recover a noticeable percentage of edge cleaning the worn brush was losing.
Does a robot mop reach edges better than a robot vacuum?+
Mop pads reach edges slightly worse than vacuums on most designs. The pad sits inside the robot's footprint, typically 2 to 3 cm from the perimeter, so the floor immediately against the baseboard stays dry. Some 2025 to 2026 models (Roborock S8 MaxV Ultra, Dreame X40 Ultra) include an extending mop pad that physically slides out toward the baseboard when the robot detects a wall. This is the most effective mop edge solution available, but still leaves the last 1 to 2 cm against the baseboard untouched.
