Waterjet Cutting (Mitred Edge) - Tile Cut-out

Simple straight cuts do not need a waterjet, because the tiler can do them on site. A waterjet helps when the job depends on shape, accuracy or expensive material. Typical situations include:

• Round and oval holes for pipes, taps, shower rails or outlets that are hard to cut accurately with a core drill
• Cut-outs close to the edge of a tile, where hand cutting could easily crack the narrow strip of tile left beside the hole
• Large-format porcelain and thin porcelain panels that do not cope well with knocks and vibration
• Natural stone and expensive decorative tiles, where spoiling a piece is not an option
• Decorative shapes, inlays and patterns made from several materials

Why is it gentler on the tile? A waterjet cuts cold and does not press on the material the way a blade does. This puts less stress on the tile, so the edge chips less. The risk of damage is not zero, though, especially with very thin pieces or tiles that already have a small hidden crack.

Most workshops follow a similar process:

1. Measuring on site: the tiler or plumber measures exactly where each opening sits in relation to the tile edges and the grout joints.
2. Drawing: the measurements become a sketch or a data file that the machine follows. For complex shapes, a full-size template is sometimes supplied.
3. Clamping: the tile is laid on the machine bed, face up or face down as the workshop instructs, and fixed so it cannot move during cutting.
4. Cutting: the thin jet of water and abrasive cuts through the material along the programmed path. For a hole in the middle of a tile, the jet first pierces the material and then follows the outline.
5. Checking and cleaning: the tile is rinsed, the dimensions and edges are checked, and sharp edges are lightly smoothed if needed.

A waterjet normally cuts straight through, at a right angle to the surface. Angled cuts, such as a mitred edge for a neat external corner, are usually made with a different method, typically on a tile saw with a tilting diamond blade. Some workshops have machines with a tilting head, so ask in advance what they can actually do.

The amount of work per tile depends on several things:

• Thickness and hardness of the material, as thick porcelain or stone cuts more slowly than a thin wall tile
• Length and complexity of the outline, meaning how much cutting there is and how many curves and corners
• Number of openings in one tile and how close they are to the edge
• Tile size, because large formats are harder to carry and clamp
• Quality of the drawing, since an inaccurate or unclear sketch means extra work and a higher risk of mistakes
• Number of pieces in one order, because setting up the machine once for several identical cut-outs is more efficient

Also allow for getting the tiles to the workshop and back, and for the waiting time until your order is done. The tiler should build this into the schedule so a half-finished wall is not left waiting.

In practice, the cut itself rarely goes wrong. The problems usually come from the information behind it. These situations come up again and again:

• Measurements are taken from the wall instead of the tile edge, so the opening does not line up with the joints
• The width of the grout joint is forgotten, so the cut-out ends up a few millimetres out
• Pipes are not yet in their final position and the plumber moves them after the tile is cut
• Nobody marks which side is the face, and the cut-out comes back mirrored
• No spare tile is ordered, even though expensive material can be hard to replace

For cut-outs around electrical fittings such as sockets or switches, the back boxes and connections are a job for a qualified electrician. The tile is simply cut to suit their position.

You will not have a waterjet at home, but you can prepare accurate measurements yourself. It saves time and frustration when the piece comes back and has to fit to the millimetre.

1. Wait until the plumber has fixed the pipes and outlets in their final position.
2. Set out the tiles on the wall or floor and decide which tile the opening falls in.
3. Measure the centre of each opening from two edges of the tile, not from the wall, and allow for the grout joint.
4. Measure the diameter or outline of the opening and add a small clearance, as your tiler recommends, so the tile slides over easily.
5. Draw a simple dimensioned sketch or make a full-size paper template.
6. Mark the face side, the laying direction and a piece number in pencil on the back of each tile.
7. Include at least one spare tile from the same batch.
8. Compare the sketch with the actual situation on site once more before handing the tiles over.

When the tiles come back from the workshop, inspect them before any adhesive goes on. A problem is much easier to sort out at this stage than on a finished wall.

• Dimensions and position of the openings match the drawing
• Edges of the cut-out are clean, with no chips or cracks
• Face of the tile is not scratched or stained by abrasive
• Narrow strips near the edge show no hairline cracks
• The tile can be dry-fitted and lines up with both the pipes and the joints
• Once fitted, there is room around pipe penetrations for sealant or a cover rose
• Number of pieces and spares matches the order