How to Drill Into Bathroom Tiles: Bit Selection, Technique, and When to Stop and Call Someone
Drilling into a tile looks like a ten-minute job. For a ceramic wall tile in a dry zone, sometimes it is. Put the same job in a porcelain shower enclosure with a waterproofing membrane behind the wall, and the variables multiply — bit type, drill speed, cooling method, fixing selection, and resealing after — and so does the cost of getting any one of them wrong.
The tile is the least of it. Tiles crack, which is expensive and annoying. Water getting behind a tiled wet area wall because a penetration wasn’t sealed properly is worse. A grab rail that works loose from a wall because the fixing didn’t engage the substrate properly is worse still. None of these failures announce themselves immediately. They accumulate quietly and surface later, when the repair bill has had time to grow.
This guide covers what actually matters when drilling into bathroom tiles — including the places where the job stops being something a careful homeowner should be doing themselves.
What’s Actually at Stake Before You Pick Up a Drill
There’s a version of this task that is genuinely simple. And there’s a version that isn’t. The difference isn’t always obvious from the outside, which is why it’s worth being clear about what can go wrong and why — before the hole is in the wall.
The most immediate risk is the tile itself. A crack in a wet area tile isn’t just cosmetic. The tile face is part of what keeps water away from the substrate and the framing behind it. A crack that runs through a tile, or along a grout joint, or within 50mm of a tile edge, gives water somewhere to go. In a shower, that somewhere is behind the tile. Replacing a single cracked tile in an existing tiled installation — finding a match, removing grout, extracting the tile without damaging the ones next to it — costs significantly more than the original drill job would have.
The second risk sits behind the tile. In any wet area under AS 3740 — shower enclosures, bath surrounds, the area around floor wastes — there should be a waterproofing membrane between the tile adhesive and the substrate. Drilling through a wet area wall penetrates that membrane. An unsealed penetration is a direct path for water to travel behind the tiles, reach the substrate, and start doing damage that won’t be visible for months. When it does become visible — at skirting level, in the ceiling of the room below, in neighbouring walls — the repair involves tile removal, substrate assessment, and re-waterproofing. Not a sealed hole.
The third risk is more specific: fixing type and load requirements. A towel rail is an accessory. A grab rail in an accessible bathroom is a safety item with minimum load ratings under AS 1428.1. These are not the same job, even if the drill bit is identical. Getting the fixing wrong on a grab rail — wrong plug type, insufficient substrate backing, inadequate load capacity — produces a failure mode with serious consequences. That distinction is what pushes certain drilling jobs into licensed trade territory regardless of how straightforward the drilling itself looks.
Related: Before drilling into a wet area wall, understand what’s behind the tile and what the compliance requirements are. See our AS 3740 waterproofing compliance guide ›
How Tile Type Changes the Approach
Ceramic, porcelain, and natural stone are not interchangeable from a drilling perspective. Hardness, density, and surface characteristics drive different bit selection and technique. The wrong bit on the wrong tile doesn’t just perform poorly — it causes the kind of failure that can’t be undone.
Clay-based, fired at lower temperatures than porcelain, more porous as a result. Harder on the outside than it looks — the glaze is tougher than the tile body beneath it, which is why the bit needs to bite through the surface before it can make progress. A carbide-tipped spear-point bit works adequately. Speed: 400–600 RPM, no hammer function.
The biggest risk is edge proximity — drilling within 30mm of any tile edge significantly increases crack risk. Mark your centre point and check the measurement twice before starting. Where it belongs: dry zone bathroom walls and powder rooms. The standard wet area specification in Australian renovations is porcelain.
Dense, hard, water absorption typically below 0.5% — the standard wet area tile in Australian renovations and the most unforgiving to drill incorrectly. The problem is heat: its density means friction builds at the cutting point faster than the tile can dissipate it. A dry bit at normal speed will fail within seconds.
Bit required: sintered diamond core. Carbide-tipped bits blunt quickly and compound the heat problem. Speed: 300–500 RPM. Water cooling throughout — not optional. Large-format (600mm+): higher crack risk during drilling. Professional tile drilling is worth considering where tiles are expensive to replace.
Marble, travertine, slate, limestone — each one different, all more demanding than porcelain. Marble chips and spalls at the entry point without correct centring and cooling. Travertine’s natural voids cause unexpected bit deflection mid-hole. Slate has cleavage planes the bit can follow instead of penetrating straight.
Bit required: sintered diamond core. Speed low, cooling continuous. Post-drill, the stone face adjacent to the fixing needs resealing — not just the silicone bead, but the stone itself. Marble and travertine in wet areas: call a professional. The tile cost alone justifies specialist labour.
Highly porous and visually distinctive. These tiles absorb moisture almost immediately if unsealed — which makes drilling and resealing around any penetration more involved than with porcelain. The sealer needs to be in place before the drill goes in, and the penetration sealed immediately after.
Where they work: dry zones and powder rooms with correct prep. In a shower enclosure, sustained direct water contact is too much for the material regardless of sealing frequency.
Non-porous and effective in wet areas as feature elements, but fiddly to drill without cracking. The glass body has no tolerance for heat at the penetration point, and the small tile format means any hole is close to a grout joint or edge almost by definition. Diamond core bit, very low speed, water cooling, slow controlled pressure throughout.
Worth noting: standard glass mosaic sheets are rarely the right place for a structural fixing. Consider whether the bracket position can be shifted to a tiled or solid substrate area instead.
The Right Drill Bit — and Why the Wrong One Fails Immediately
Standard twist drill bits do not work on tiles. The geometry is wrong — a twist bit is designed to cut by shearing metal fibres. Tile is ceramic or stone. The bit rotates against the surface, generates friction, either slides off the glaze or starts generating heat it can’t dissipate, and the tile suffers before the hole does. This isn’t a question of technique. The tool is wrong for the material.
Two bit types are appropriate for bathroom tile work. Carbide-tipped spear-point bits — adequate for ceramic, marginal on soft natural stone, not suitable for porcelain. Sintered diamond core bits — correct for porcelain, marble, travertine, slate, and glass mosaic. The cost difference between the two is small. The cost difference between a correct bit and a cracked tile is not.
A note on diamond bit quality: cheap sintered bits lose their cutting coating quickly on dense porcelain. On anything harder than standard ceramic, a quality bit is not where to economise. A bit that stops cutting forces the operator to increase pressure — which is when tiles crack.
Speed, Pressure, and Cooling — Where Most Drilling Failures Actually Start
Porcelain’s density is the problem. It doesn’t conduct heat away from the cutting point quickly. Friction builds at the drill tip faster than the tile can dissipate it, and once the surface exceeds a critical temperature, micro-fractures propagate through the tile body. Often invisibly at first. Under thermal cycling from daily shower use, those fractures develop. The tile looked intact on the day. It cracked six weeks later. The heat was present from the moment the bit stopped being cooled.
Speed setting: 300 to 500 RPM for porcelain and natural stone, 400 to 600 for ceramic. No hammer function. Variable-speed drills should be set to their lowest range before contact — not dialled back after the bit has already been spinning at full speed. A corded drill with consistent low-speed torque is preferable to a cordless drill for this work, because cordless tools under load can surge in speed in ways that aren’t always obvious to the operator.
Cooling is not optional for porcelain and stone. The simplest approach: build a dam around the drilling point with plumber’s putty or similar, fill it with water. The bit should be cutting through water for the full duration of the hole. An alternative — a helper with a wet sponge maintaining water contact at the drilling point throughout — works, but requires coordination and doesn’t stop if attention drifts. The dam method is more reliable.
On pressure: light and consistent. Let the bit do the work. The instinct when a bit slows or stops making progress is to lean in harder. That instinct is wrong. If progress stalls, the cause is almost always a worn bit or incorrect speed — not insufficient force. More pressure on a struggling bit is how tiles crack from the inside. Check the bit for wear, reduce speed if it’s crept up, maintain cooling. Don’t push through.
Important: Never use hammer action on any tile surface. Percussion impact fractures tile bodies regardless of bit type or tile hardness — it’s not a setting that needs to be turned down, it needs to be confirmed off before the drill makes contact. A drill with accidental hammer mode engaged will crack the tile before the hole is through the glaze.
Marking the Centre and Starting Without the Bit Walking
A glazed tile surface gives a drill bit nothing to bite. The glaze is smooth and hard, and a rotating bit pressed against it will skate — moving laterally across the face before it can establish a grip. The track it leaves cannot be repaired. Preventing it is simple, but it requires doing it before the drill starts spinning.
Two methods work. Masking tape applied to the tile face at the drilling point: the tape gives the bit tip enough friction to start without walking. Mark the centre through the tape. Start the drill slowly before applying pressure. The second method — a centre punch indent made with a carbide-tipped tile punch — creates a small depression in the glaze that holds the bit tip in place. More reliable on polished porcelain where tape can slip. For anyone who hasn’t done it before, the tape method first.
One more thing about starting: begin with the drill stationary. Position the tip in the marked point, establish contact with no rotation, then start the drill at the lowest speed setting. Don’t bring the bit in from above at speed and hope it lands in the right place.
Tile type confirmed, bit selected
Carbide for ceramic. Sintered diamond for porcelain or stone. Standard twist bits excluded before the drill comes out.
Speed set, hammer mode confirmed off
300–500 RPM for porcelain and stone, 400–600 for ceramic. Hammer mode off and physically verified — not assumed.
Cooling method prepared before starting
Water dam built or assistant in position with wet sponge. Cooling begins on first contact and continues until the bit is clear.
Hole position measured — 30mm minimum from all tile edges
Measured horizontally and vertically. Bracket position confirmed on the tile before anything is marked.
Marking applied at the drilling point
Masking tape over the marked centre, or carbide punch indent in the glaze. Bit positioned at the mark before the drill starts.
Substrate identified behind the tile
Stud confirmed if load-bearing. Solid masonry, fibre cement over cavity, or timber stud each requires a different fixing type.
Drilling Into the Grout Joint — When It Helps and When It Doesn’t
Drilling into the grout joint rather than the tile face is common advice, and in certain situations it’s the right call. Grout is softer than tile, doesn’t require specialist bits, and drilling into it avoids the risk of cracking the tile itself. For a light-duty fixing on a dry-zone ceramic wall where the bracket position happens to align with a grout joint, there’s no reason not to use it.
The problems come when this advice is applied too broadly. Brackets have fixed hole spacing — they’re not designed around tile layouts. If the grout joint doesn’t fall where the fixing needs to go, the advice becomes moot. More significantly: grout doesn’t carry load. Whether you drill into the joint or the tile face, the fixing must engage the substrate behind. A nylon plug in grout is not a different structural outcome from a nylon plug in tile if both are going into the same cavity. The grout is incidental.
In a wet area, drilling into a grout joint carries the same penetration obligation as drilling into the tile face. The waterproofing membrane behind doesn’t know which surface the bit came through. Both require the penetration to be sealed correctly around the fixing when the job is done. And if the grout in question is epoxy rather than cement-based — increasingly common in higher-end bathroom renovations — it’s significantly harder and requires diamond bits regardless. Standard carbide on epoxy grout will blunt before the hole is through.
Choosing the Right Fixing for Tile and Substrate
A standard plastic expansion plug is designed to set in solid masonry or timber. It expands outward as the screw is driven, and the resistance of the surrounding solid material is what holds it. In a cavity wall behind fibre cement sheet — which is what most tiled bathroom walls are — there’s no solid material to push against. The plug expands into air. It may feel solid when it goes in. It will work loose.
Tile-specific fixings account for the two-material reality of a tiled wall: the tile body itself, and whatever is behind it. Toggle bolts set in the cavity. Nylon anchors sized to grip fibre cement sheet at the correct diameter. Through-bolts to a structural stud for load-bearing fixings. The fixing type follows from the substrate, which follows from knowing what’s behind the wall before the drill goes in. Probing with a thin wire into a test hole, or using a stud finder before starting, is not overcaution — it’s how you select the right plug.
Related: Grab rail installation in an accessible bathroom carries specific load and substrate requirements under AS 1428.1. See our NCC bathroom standards guide ›
What Happens When the Drill Goes Through the Membrane
In a compliant wet area — any shower enclosure, bath surround, or water-affected zone under AS 3740 — there’s a waterproofing membrane between the tile adhesive bed and the substrate behind. It’s not optional and it’s not visible from the tile face. It exists between the two layers, doing a job that isn’t noticed when it’s working and becomes very noticeable when it isn’t.
Drilling through a wet area wall penetrates that membrane. The bit goes through the tile, the adhesive, and the membrane, and exits into whatever is behind — fibre cement, timber framing, masonry. That penetration is now an unsealed path for water. Every time the shower runs, water that reaches the tile face adjacent to the fixing can track down the fixing, through the penetration, and into the substrate. Not in a flood — in the quantities that wet surfaces always produce. Quietly and consistently.
The damage accumulates in the substrate and the framing before it becomes visible externally. By the time efflorescence appears in grout joints, or the plasterboard in the adjacent room feels soft, or mould appears at skirting level, the penetration has been leaking for long enough that the repair involves tile removal, substrate replacement, and re-waterproofing. The gap between “something wasn’t sealed correctly” and “we need to rip out the shower” is often eighteen months to three years.
Occasionally, drilling a wet area wall reveals that there’s no membrane at all. The bit passes through tile and adhesive and lands on untreated timber or standard plasterboard. That’s a pre-existing compliance problem — the area wasn’t waterproofed to standard in the first place. The fixing job becomes secondary. The membrane absence is what needs addressing.
Related: Penetration requirements for wet areas sit within the broader waterproofing compliance framework. See our AS 3740 waterproofing compliance guide ›
Sealing the Penetration After the Fixing Goes In
The silicone bead around a fixing in a wet area is not a finishing touch. It is what closes the penetration. Without it, the gap between the fixing and the tile is an open path for water to enter the hole, travel through the tile and adhesive, and reach the membrane — or bypass it entirely if the penetration goes through.
Product: wet-area rated, mould-resistant silicone. Not paintable acrylic. Not general-purpose silicone from the hardware mixed section. Not grout. Apply the bead between the fixture flange and the tile face, tool it to a clean concave profile, and allow full cure before the area is used. Twenty-four hours minimum — read the product data sheet.
Natural stone tiles require one additional step. The drilling breaks the sealer originally applied to the stone face, and the tile body adjacent to the penetration is now unprotected. Stone will absorb water through an unsealed face. Before applying the silicone bead around the fixing, re-seal the stone surface within 50mm of the hole with an appropriate penetrating stone sealer. This is a separate step from the silicone — different product, different purpose.
Related: Sealant product selection and application — including what works at different wet area locations. See our grout and sealants guide ›
Have a question about what’s behind your bathroom tiles, or whether the fixing you’re planning is suited to the substrate? We connect homeowners with experienced, vetted renovation specialists across NSW and ACT who can assess the site before work starts. Lifestyle Bathrooms is a referral and connector service — not a licensed contractor. Request a free consultation ›
Drilling Failures That Turn Up Later — and What Caused Them
Most drilling failures share one characteristic: the conditions that produced them were present on the day the work was done. They just didn’t surface until later — sometimes much later — and the repair costs have usually compounded by the time they do.
Cracked tile at or after drilling
A tile that cracks during drilling is a technique failure. A tile that cracks weeks or months later, with a fracture line running from the drill hole, is almost always a heat failure — a micro-fracture that formed when the bit overheated on porcelain and propagated under daily thermal cycling before it became visible.
Neither can be repaired in place. The tile has to come out. In an existing installation, that means finding a matching tile from the same batch (not always possible), removing surrounding grout without damaging neighbouring tiles, extracting the cracked tile cleanly, inspecting and if necessary re-waterproofing the substrate, and retiling. The cost is a multiple of what a sintered diamond bit and a water dam would have added to the original job.
A fixing that felt solid and then didn’t
Standard expansion plugs in cavities spin or compress rather than setting. The fixing passes a tug test on installation. Under repeated load — a towel rail with wet towels, a soap holder grabbed for balance — it works loose. On a grab rail, this is not an inconvenience. It’s a safety failure.
Fixing this requires removing the fitting, plugging and resealing the original holes, relocating to a position where substrate backing can be confirmed, and reinstalling with correct fixings rated to the load requirement. All of which could have been avoided by identifying the substrate before the drill came out.
Water damage behind a wet area wall
An unsealed penetration in a wet area is invisible until the damage behind it is significant enough to show externally. By the time it does — efflorescence at grout joints, soft plasterboard on an adjacent wall, mould at skirting level, a ceiling stain in the room below — the water has been tracking behind the tiles for long enough that the substrate repair is substantial. Tile removal, substrate assessment, re-waterproofing, retiling.
The penetration that caused it was a drill hole that wasn’t sealed. The silicone tube costs a few dollars. The repair costs significantly more.
Grout cracking around the drill hole
Vibration from drilling at too-high speed, or with any hammer engagement, transmits through the grout joint network adjacent to the hole. The grout is rigid; the vibration creates hairline fractures in the joints immediately surrounding the penetration. In a wet area, fractured grout adjacent to an unsealed fixing is two simultaneous water entry paths. Both need attention: the penetration sealed with silicone, the damaged grout raked out and properly reinstated.
Related: See the full list of installation shortcuts and conditions that lead to these outcomes. See common waterproofing shortcuts ›
Where This Stops Being a DIY Job
Some drilling jobs in a bathroom are genuinely within a careful homeowner’s reach. A towel ring on a dry-zone ceramic wall tile, correct bit, correct speed, adequate sealing — that’s a manageable task with the right preparation. The checklist in the next section is designed for exactly that kind of job.
Grab rails are different. Under AS 1428.1, grab rails in accessible bathrooms must meet minimum load ratings — 1.1 kN horizontal as a baseline, higher in some applications. Meeting those ratings requires substrate backing: a structural nogg or solid backing plate behind the wall lining, not a fixing into fibre cement sheet alone. Installing a grab rail correctly in an existing bathroom involves confirming or providing that backing, waterproofing the penetration to standard, and installing fixings rated to the load requirement. That is licensed trade work. The drilling itself is incidental.
Any wet area where the drill reveals that the waterproofing membrane is absent or compromised is a different problem. The penetration stops being the issue — the membrane is. Attempting to seal a penetration in a non-compliant wet area addresses the symptom while leaving the underlying problem in place. The membrane needs to be dealt with first.
Large-format porcelain — 600mm and above — significantly raises the stakes on any drilling work. The tiles are expensive. Cracking one during drilling is expensive. The replacement process is disruptive. For a single precision hole in large-format porcelain, the cost of professional tile drilling is straightforwardly cheaper than the risk of getting it wrong.
Before You Start Drilling: Nine Things to Confirm
This is not the technique compressed into a list. It’s the questions that determine whether the job is safe to proceed and what it requires. Each item has a consequence if it’s skipped.
Tile type confirmed, bit selected
Carbide for ceramic. Sintered diamond for porcelain and all natural stone. If you don’t know what type of tile is installed, check the documentation or ask. Don’t guess.
Drill speed set, hammer mode confirmed off
400–600 RPM for ceramic, 300–500 for porcelain and stone. Hammer mode confirmed off and physically checked — not assumed. Verify before the drill comes near the tile.
Cooling prepared before starting
Water dam built or assistant ready with wet sponge. Not improvised mid-hole. Cooling begins with first contact and doesn’t stop until the bit is clear.
Hole position measured — 30mm minimum from all edges
Measured both horizontally and vertically. Bracket position confirmed before marking. Not estimated or eyeballed.
Marking applied at the drilling point
Masking tape over the marked centre, or carbide punch indent in the glaze. Bit positioned at the mark before the drill starts.
Substrate identified behind the tile
Stud confirmed for load-bearing fixings. Solid masonry, fibre cement over cavity, or timber stud each requires a different fixing type.
Wet area status confirmed
If in a wet area under AS 3740, sealing the penetration is a required completion step — not optional and not something to defer.
Correct fixing type selected for the substrate
Toggle bolt, nylon anchor, or through-bolt to stud based on what’s behind the wall and what load the fixing needs to carry. Standard expansion plugs excluded from cavity applications.
Wet-area silicone on hand before starting
Mould-resistant, wet-area rated silicone ready to use. The penetration gets sealed when the fixing goes in — not at the end of the day, not when there’s time.
Common Questions
Yes, provided the bit is correct and the settings are right. The drill itself isn’t the constraint — a standard variable-speed drill with a sintered diamond bit, set to 300–500 RPM with hammer mode off and continuous water cooling, will drill porcelain effectively.
What doesn’t work: any standard twist bit, carbide-tipped bits on dense porcelain, any speed above the low range, and any use of hammer action. A regular drill at normal speed with a standard bit on porcelain will fail immediately — not because the drill is inadequate, but because the setup is wrong.
Thirty millimetres from any tile edge is the practical minimum. Within that distance, the tile body doesn’t have sufficient mass to absorb the stress of drilling without cracking, particularly in ceramic and natural stone. Porcelain is more tolerant but still subject to edge proximity failure — the risk increases noticeably below 25mm.
If the bracket requires holes closer than 30mm to a tile edge, that’s worth addressing before drilling rather than after. Sometimes the bracket can be shifted slightly; sometimes the tile layout means there’s no good position. When there’s no good position, that’s usually the conversation that leads to a professional assessment.
In a wet area — any shower enclosure, bath surround, or water-affected zone defined under AS 3740 — yes. Sealing is a compliance obligation, not a finishing preference. The correct product is wet-area rated silicone applied between the fixture flange and the tile face, closing the gap around the fixing. Allow full cure before the area gets wet.
Outside a wet area — a dry zone bathroom wall, toilet room, or hallway — sealing is good practice regardless. Water reaches places in a bathroom that aren’t technically defined as wet areas, and an unsealed penetration is an opportunity for it to get behind the tile. The silicone tube is cheap. The repair if water tracks in isn’t.
For light-duty fixings on ceramic walls where the grout joint happens to fall in the right place, drilling into grout avoids tile cracking risk and works adequately. But grout doesn’t carry load — the fixing is going into the substrate behind, and whether it passes through grout or tile face to get there doesn’t change what the plug engages.
The practical limitation is positioning. Bracket hole spacing is fixed by the product, not by the tile layout, so the grout joint often isn’t where the bracket needs it to be. And in a wet area, the penetration sealing obligation is the same regardless of which surface was drilled. Epoxy grout — increasingly common in higher-end renovations — is significantly harder than cement-based grout and requires diamond bits regardless.
In a bathroom that needs to meet AS 1428.1 accessibility requirements — whether under the NCC or as part of an accessible housing renovation — grab rail installation is licensed trade work. The minimum load rating (1.1 kN horizontal, higher in some contexts), the substrate backing requirement, and the wet area penetration compliance together make this a job that requires more than correct drilling technique.
For a grab rail being added to a standard bathroom as a personal safety measure, the same structural and sealing requirements apply even without formal compliance obligations. The consequence of a grab rail pulling from the wall under load is the same whether the bathroom is certified accessible or not. Confirming stud or backing plate location and using correctly rated fixings is the minimum. If that assessment can’t be made confidently, the job is worth putting in front of a professional.
Not Sure What’s Behind Your Bathroom Tiles?
If you’re uncertain about the substrate, the wet area status, or the load requirements for the fixing you’re planning — that’s the right time to get a specialist view, not after the hole is in. We connect homeowners and property professionals in NSW and ACT with vetted renovation specialists who can assess your specific situation before work starts.
Lifestyle Bathrooms is a referral and connector service, not a licensed contractor. We connect homeowners, investors, and property professionals in NSW and ACT with vetted bathroom renovation specialists.