Trim, mitre or raw edge: what should finish a tiled corner?

Metal or PVC trim, fitted before the tile against the exposed edge, giving a consistent factory-finished line and protecting the tile edge from chipping.

A mitred joint, where two tiles are cut at 45 degrees and meet at the corner, giving a continuous run of tile with no visible trim at all. This is the higher-end finish for external corners on rectified porcelain in particular.

A raw or 'pencil' finished tile edge, using a tile with a factory-glazed or bullnose edge designed to be left exposed. This works well with tiles specifically manufactured for it and poorly with anything else.

Leaving a standard cut tile edge exposed with no trim, mitre or finished edge is the fourth option, and it is the one we would generally advise against on any visible corner, because the unglazed edge chips and marks over time.

Mitred corners suit large-format rectified porcelain particularly well, where the tile edge is dead straight and the joint reads almost seamlessly once grouted. On a shower niche or an external corner in a feature area, this gives the cleanest possible finish.

Mitring takes real skill and a well-set-up wet saw; a slightly out-of-square cut leaves a visible gap or a proud edge that is far more noticeable than a trim would have been. It also takes considerably longer than fitting a trim strip, which is reflected in labour cost.

We would generally avoid mitring on thinner ceramic wall tile, where the body of the tile can be more prone to small chips along a fine mitred edge, and on tiles with a pronounced bevel, where the mitre geometry does not work cleanly.

Aluminium is the default we specify unless there is a specific design reason to move away from it: it is corrosion-resistant, comes in a wide range of finishes and is straightforward to cut cleanly on site.

Brass trim has become popular alongside the trend for brass taps and shower fittings, and genuinely does age attractively rather than just tarnishing, but it costs several times more per metre than aluminium and needs mitred internal corners of its own to look right.

An external corner takes knocks from mop handles, hoover attachments and general daily traffic that an internal corner never sees, which is why chipped tile edges cluster there.

Without a trim, mitre or finished edge, the raw cut edge of a ceramic tile is unglazed body material, which is more porous and considerably weaker than the glazed face. It is the first place moisture gets in and the first place a chip appears.

On floor-to-wall external corners in a wet area, a trim also gives a defined, consistent line for the silicone movement joint that should sit there instead of grout, which helps the corner cope with the slight ongoing movement every floor and wall has.

Trim should sit flush with the tile face, not proud of it or sunk below it, and should run in a genuinely straight line rather than wandering with the wall behind it.

Mitred corners should show a fine, consistent grout line all the way down, not a visible gap at the top that closes up towards the floor, which usually indicates the cut was not checked against a level line before fixing.

Trim should be cut to length with a mitre at any internal corner return, not simply butted together, and end caps should be used wherever a trim run terminates in open space rather than into another surface.