How to sand inside corners on drywall or plasterboard without a ladder

Inside corners (internal corners, if you're in Australia) are the slowest part of sanding a house. Every corner is two faces meeting at an angle you can't get a flat block into, so most of us end up on a ladder with a folded sheet of paper or a corner sponge, working a metre at a time, then climbing down, moving the ladder, and climbing up again. On a full house that is a lot of ladder.

This is how to do it from the floor, and what you need.

The problem with the usual ways

Hand sanding with folded paper gives you good control but no reach. You sand the bottom half from the floor, then do the top half off a ladder or a trestle. Pressure is uneven, so you get flat spots where you pressed hard and ridges where you didn't.

Corner sanding sponges are quicker to hold but they round the corner off, and they clog.

Pole sanders with a flat head can't get into the apex of the corner at all. You end up sanding the two faces separately and leaving the join line for a hand sand anyway.

Powered drywall sanders are fast on walls and ceilings but they are the wrong shape for an internal corner, and the heavy ones are hard work overhead.

Sanding a corner from the ground

A pole-mounted corner sander changes the job. The head is shaped to the corner, so it sands both faces at the same time, and the pole gives you the reach to run floor to ceiling without a ladder. Here is the method with the Morph Sander.

1. Mount it on a handle. On a budget? The Ball Adaptor is a fitting that lets you run the Morph Sander on any standard paint pole. Otherwise it mounts on a standard corner finishing handle, the ball-joint handle you run a flusher, glazer or angle head on, such as the Can-Am Corner Finisher Handle or the Columbia Angle Head Handle.
2. Fit the pad. Fold a 150 grit Elite corner pad over the head so the crease sits in the apex. The rubber Hyperflex tip behind it does the conforming, so you don't need to force it.
3. Start at the top. Put the head into the corner at the ceiling and let the swivel settle it onto both faces. Use the pole's length, not your arms, to hold it there.
4. Run it down in one pass. Light, even pressure. The head does the work on both faces at once; pushing harder only loads the tip. One pass down, one pass back up, and move to the next corner.
5. Check with a light. Hold a torch along the corner. If you can see a line at the apex, it was a thick set, not a sanding problem; a second pass fixes it.

The ladder stays on the truck. The reviews on the Morph Sander page put it in tradesmen's own words; one calls it the tool that "makes sanding inside corners a breeze".

What you need

• Morph Sander Corner Sander XL. The corner head. One Hyperflex tip is included.
• A handle or a pole. Any standard paint pole plus the Ball Adaptor, or a standard corner finishing handle such as the Can-Am Corner Finisher Handle or the Columbia Angle Head Handle.
• Elite corner sanding pads, 150 grit. Five to a pack. The 150 grit paper is thicker, so it takes longer to split.
• Optional: the Morph Master for the joins and the flats, so the whole room is done off the pole.

The Morph System bundle puts the corner sander, the pole sander and a pack of pads together for less than the three bought separately.

Where this came from

The Morph Sander was built by James Weihoenig, a Brisbane plasterer (Australia's word for a drywall taper and finisher), because he was sick of ladders. It is patent pending and has sold more than 5,000 units to tapers, finishers and plasterers in Australia, the United States and Canada. CSR Building Supplies in Canada wrote about why drywall finishers there are switching to it. If you want to see it in use, the videos on the Morph Sander page show a corner start to finish.