Quick Answer

Corner work needs a concrete grinder with a squared-edge dust shroud or a dedicated edging grinder that reaches within about 5 to 10 mm of the wall. A standard round shroud leaves a crescent of unground concrete against every wall, so you either swap to a flat-side shroud or finish edges by hand. Keep the vacuum at full rated suction, about 250 to 300 CFM at the tool, and protect walls with tape and poly sheeting so escaping dust does not bury the finished trim. Budget about 20 to 30 percent of a small room on the perimeter alone.

Why Corners Fight Standard Shrouds

A round grinding shroud is built to contain dust around a rotating cup wheel, but its curved skirt cannot sit flush against a straight wall. The gap between the skirt and the wall leaks dust and leaves an unground crescent that handheld polishers must later chase. On a room with 20 m of wall, that crescent is a slow, dusty job unless the machine is set up for edges from the start, and the longer you leave it, the harder it is to blend back into the open floor.

Shroud shapes for edge work

Flat-side or square shrouds replace the curved skirt with one straight edge designed to ride against the wall. Some are removable, so you run the round shroud in the open bay and swap to the flat side for the perimeter. Other machines come as dedicated edging grinders with a small wheel offset past the body, which reaches true corners that walk-behind shrouds cannot enter, and they are the right tool for rooms ringed by built-in cabinets.

Tooling that follows the wall

Use a cup wheel with a continuous diamond rim or a segmented row that leaves no large gaps at the edge. PCD shoes for coating removal can jump and chatter when half the wheel rides the wall, so keep those for open floor work and finish edges with a conventional diamond cup. A rim that leaves a skip every few centimeters will telegraph straight through to the final floor finish and cost you a callback.

The Wall-Follow Technique

Lower the shroud until the straight edge contacts the wall, then walk the machine along the seam at the same pace you use on open floor. Do not press the wheel sideways into the wall; let the straight edge track. Overlap the open-floor passes by about 50 mm so the two scratch patterns blend, and go around columns and boxouts with the corner of the shroud rather than tilting the machine. Tilting buries one edge of the wheel and leaves a gouge you will repair by hand at the end of the day.

• Tape 50 mm of painter tape along the base of walls so the skirt does not scuff paint as it tracks along the seam.
• Run the vacuum hose straight back from the machine, not across the path, so it never pulls the shroud off the wall mid-pass.
• Check the skirt weekly; a worn skirt loses suction and dumps dust exactly where you can see it on the finished base.

Controlling Negative Pressure and Leakage

Dust containment only works if the shroud is the lowest-pressure point in the system. A shop vac rated under 200 CFM will not keep up with a 480 mm grinder and will push fine dust out through every seam. Use an industrial dust extractor with enough CFM for the machine, empty it before it half-fills, and keep filters clean so suction does not fade mid-edge. Seal obvious leaks with foam gaskets where the shroud meets the deck, and listen for the telltale whistle that marks a leaking skirt seal. When the extractor bags fill, the pressure drops across the whole system, so change bags before the gauge says empty rather than after the suction has already softened. On multi-room jobs, run a short edge pass in the first room, inspect the wall base, and tune the shroud position before committing to the whole perimeter.

Protecting Walls and Finished Work

Even a well-sealed shroud leaks a fine dust haze at corners. Mask the lower wall with poly sheeting held by low-tack tape, and lay floor protection over any finished area the crew walks through. At break time, wipe the wall base with a damp cloth before the dust dries into a film that later coats cannot cover. Plan to vacuum the whole perimeter at the end of each grit stage so dust from a coarse pass never gets ground into a fine one, and remember that silica dust settles on ledges and shelves as well as floors.

FAQ

Can I grind right up to the wall without a flat shroud?

You can grind close but never flush; the crescent left by a round shroud still needs a handheld edge grinder to finish to the wall line.

How much suction do I really need?

Match the extractor CFM to the grinder rating, and never run a dry grinder without extraction; the silica dust risk is not worth the speed gain.

What about inside true corners?

Inside corners where two walls meet are unreachable for any shroud, so plan on a handheld angle grinder with a dust shroud attachment for the last 100 mm along both walls.