Cutting Holes in Tiles & Paving

Cut-outs are for square and irregular shapes: a notch in the corner of a tile, or a cut-out around a toilet, a shower channel, an access panel or a square electrical box. They are usually made with an angle grinder fitted with a diamond blade. For straight notches, a tile cutter and grinder are often combined.

Drilled holes are round holes made with a diamond core bit, sometimes called a diamond hole saw. The edge is cleaner and the hole perfectly round. They suit pipes, tap connections, round socket boxes and wastes. For larger diameters, usually above about 15 cm, the core bit is often combined with a grinder or a cutting attachment.

The material makes a big difference too:

• Ceramic wall tiles have a softer, porous body, so they are easier to work and need less powerful diamond tools
• Porcelain tiles are very hard and absorb almost no water, so they can only be worked with diamond tools and water cooling, otherwise the tool overheats and the tile can crack
• Natural stone and marble are brittle, so they are drilled slowly and smoothly

Most mistakes happen during measuring, not drilling. The tiler therefore measures the position of the hole from the last laid row and allows for the width of the joint. The point is marked on the tile with a pencil or marker. For round holes, a paper template or the cover plate that will hide the hole often helps.

The tile is placed on a flat, slightly soft base such as a rubber mat or cardboard and secured so it cannot slide. When drilling with a core bit, the bit is first held at an angle of roughly 45° to cut a small groove so it does not skate across the glaze. It is then slowly brought upright. The drill runs at low speed, with gentle pressure, hammer action switched off and water to cool both the bit and the tile and to keep dust down.

For cut-outs with a grinder, shallow cuts are made along the outline first and then gradually deepened. Inside corners are finished carefully so the tile does not snap at its weakest point. Small holes for screws and wall plugs are made with a thin diamond tile drill bit. A piece of masking tape over the mark stops the bit slipping at the start. Finally, the edges are smoothed with a diamond file, a sanding sponge or fine abrasive paper.

Two holes that look the same at first glance can take very different amounts of time. The effort depends mainly on:

• Hardness and thickness of the material, because thick porcelain takes much longer to drill than thin ceramic tile and wears the tools more
• Size and shape of the hole, since a small round hole is quick, while a large or irregular cut-out needs more cuts and more finishing
• Position of the hole, because a hole close to the edge or in the corner of a tile raises the risk of cracking
• Large-format tiles, which are awkward to handle, and every broken tile is a bigger loss
• Holes in tiles already fixed to the wall, where the tile cannot be clamped, water runs down the wall and the routes of pipes and cables must be known
• Number of identical holes, because with a series the tools are set up once and the work flows more smoothly

• Wrong tools. A masonry bit or hammer action chips the glaze and tends to shatter porcelain rather than drill through it. Tiles need a diamond drill bit or core bit.
• Drilling dry. Without water the bit overheats and blunts quickly, and the tile can crack from the heat. If cooling is not possible, work in short bursts and let the tool cool down.
• Too much pressure. Pushing hard to speed things up often snaps the tile just before the cut is finished. Let the tool work at its own pace.
• Poor measuring. A hole in the wrong place will not be covered by the cover plate and the tile is wasted. The old rule applies: measure twice, cut once.
• Wrong diameter. The hole should be a little larger than the pipe to leave room for flexible sealant, but smaller than the cover plate or cap.
• Drilling blind into the wall. When adding holes to finished tiling, you need to know where pipes and cables run, otherwise you risk drilling into them.

You can manage one or two holes in ordinary ceramic wall tiles yourself, for example for a pipe or a bracket. Leave porcelain, large formats and cut-outs for drains and channels to a tiler. Sockets and switches fitted into cut-outs must be connected only by a qualified electrician. When drilling into tiles already on the wall, switch off the relevant circuit at the consumer unit and make sure you know where the pipes and cables run.

1. Measure the diameter of the pipe or fitting and choose a diamond core bit slightly larger.
2. Measure the centre of the hole, including the joint, and mark it on the tile.
3. Lay the tile on a flat rubber mat or cardboard and secure it so it cannot move.
4. Switch off the hammer action on the drill and set a low speed.
5. Start with the bit at an angle to cut a groove, then slowly bring it upright.
6. Drill with gentle pressure and keep the spot wet, for example with a spray bottle.
7. Ease off the pressure just before breaking through so the back edge does not chip.
8. Smooth the edge with a diamond file or fine abrasive paper and clean the tile.
9. Dry-fit the tile in place before fixing it.

Wear safety glasses and gloves throughout. When cutting with a grinder, wear a dust mask as well, because tile dust contains fine silica.

When you take over the tiling, look at these points:

• Holes are in the right place and outlets line up with the tap or box
• Edges are smooth, without cracks or chipped glaze
• The gap around pipes is even and the cover plate or cap hides it completely
• Around penetrations in wet areas the waterproofing is intact and the joint is filled with flexible sanitary sealant
• No hairline cracks run from the hole towards the edge of the tile
• At a floor drain or shower channel the tiles meet it without a step and fall towards the outlet
• The area is clean of dust and cutting slurry