When your benchtop is telling you something.

A crack out of a cut-out corner.

This is far and away the most common failure we get called to, and it is almost always a fabrication story rather than a homeowner one. Cut a square corner into a cooktop or sink opening and you have created a stress concentration at a single point. Add heat cycling from the cooktop above, add a bit of flex in the cabinets below, and over a few years a hairline walks out of that corner and keeps going. A radiused corner, a proper support rail across the opening and an expansion gap around the appliance prevent it. That is why a cheap cut-out is not a bargain.

A crack across an unsupported span.

Twenty millimetre engineered stone is strong in compression and unforgiving in bending. An overhang past about 300mm with nothing under it, a dishwasher gap with no rail bridging it, or a span where the cabinetmaker left a run without a mid-support, will eventually crack across the thin section. Someone leaning on the breakfast bar is usually blamed. The lean was not the cause; the missing steel was.

Thermal shock.

Engineered stone contains resin. Put a pot straight off a gas burner onto it and you can scorch it or, on a cold morning, shock it hard enough to craze the surface. Porcelain shrugs this off far better, which is one of the reasons we recommend it for heavy cooks. Either way, a trivet costs $15 and a benchtop does not.

Is it growing?

The single most useful thing you can do is mark each end of the crack with a pencil and write the date next to it. Come back in a month. A crack that has not moved is a cosmetic problem you can schedule. A crack that has grown is telling you the cause is still active, and filling it will achieve nothing until you find out what is moving.

• Dark rings around the tap on granite or marble. The sealer has worn through and the stone is drinking. Do the water-drop test: if a drop soaks in and darkens within a few minutes rather than beading, it needs resealing. Engineered stone and porcelain never need this.
• Dull, slightly rough patches on marble. That is etching, not staining. Lemon, vinegar, wine and most bathroom cleaners eat the calcium carbonate. It is chemistry, not neglect, and it is why marble is a lifestyle choice.
• Cloudy film that keeps coming back. Usually mineral deposit from hard water plus a cleaner leaving residue. Warm water, pH-neutral cleaner, dry it off.
• Fading or chalking on a dark bench in a west-facing window. The harsh western light through a Dawesville or coastal Falcon kitchen is brutal, and some darker engineered stones lose colour over years. Porcelain is UV-stable and does not. The full comparison is on the porcelain vs engineered stone page.
• Salt film on an alfresco bench. Cosmetic if you rinse it, corrosive to the fixings underneath if you never do.
• Swelling at the sink edge on laminate. Water has got into the particleboard core. There is no repair for that; the top is done.

Triage it simply. Urgent: loose sink, black silicone, a growing crack. Book it: chips, a stalled hairline, etching, worn sealer. Replace: a cracked top that has already been repaired once, or laminate that has swelled. If it comes to replacement, the honest ranges start around $480/m² installed for entry engineered stone and $900 to $1,300/m² for porcelain, with a typical 4 to 5m² kitchen benchtop landing at $4,200 to $6,500 in mid-range material. There is one modern catch worth knowing before you plan a repair on an older engineered stone top, and it is covered on the engineered stone silica rules page.

A worked example on repair versus replace. A Greenfields kitchen came to us with a crack out of a cooktop corner that had already been filled once and had moved again. Repair number two would have been about $450. Replacement was 4.5m² of mid-range engineered stone at $750/m², so $3,375, plus an undermount sink cut-out ($280), a cooktop cut-out ($180) and controlled removal of the legacy top ($350), landing at $4,185. We told them to spend the $450, because the crack had stalled once the loose support rail under the cooktop was packed and refixed, and the cause was fixable for the price of an hour. Had the crack still been walking, that $450 would have bought them nothing and the $4,185 was the only honest answer. Find the cause first. Full rates are on the pricing page.

If a stepped join does turn out to be structural, that is the one case where this stops being a benchtop conversation. Slab and footing performance is governed by AS 2870, and on the estuary fringe a stepped join can be the first visible symptom of it. That is a matter for a structural engineer, not your local government: neither the City of Mandurah nor the Shire of Murray, which covers Pinjarra, Ravenswood and South Yunderup, issues a permit for replacing a benchtop, and nor will either of them diagnose why your house is moving. Get the structure assessed, then put stone back on it.

Why is my stone benchtop cracking near the cooktop?

Because the corner of a cut-out is the weakest point on the whole bench and it is being asked to do too much. A cut-out corner that was cut square instead of radiused concentrates stress at a single point, and repeated heat cycling from the cooktop plus any flex in the cabinets underneath will eventually walk a hairline crack out of that corner. It is a fabrication issue nine times out of ten, not something you did. Radiused corners, proper support rails and an expansion gap prevent it, which is why we detail cut-outs the way we do.

My benchtop join is opening up. Is that serious?

It depends on what is moving. A join that has a fine dark line appearing is usually just the join adhesive shrinking or failing, which is annoying but repairable in an hour. A join that is visibly stepped, where one side sits higher than the other, means the cabinets or the floor beneath have moved, and refilling the join will not fix it because it will open again. Around the estuary fringe at Coodanup and Dudley Park where the ground is softer, we do see genuine structural movement. Work out which one you have before paying anyone to fill it.

Why has the silicone around my splashback gone black?

Black silicone is mould, and mould means water is sitting where it should not. Sometimes it is only surface mould from steam and a poorly ventilated kitchen, and it cleans or gets recut. More often it tells you the seal has failed and water is getting behind the splashback into the substrate. Left alone that swells the cabinetry and can rot a wall. It is a cheap fix early and an expensive one late, so treat blackening silicone as an early warning rather than a cosmetic annoyance.

My undermount sink feels loose. What do I do?

Stop filling it and get it looked at this week. An undermount sink is held to the underside of the stone by adhesive and mechanical clips or a support rail, and a full sink of water plus dishes is a serious load. Once you can feel movement, the bond has already partly failed, and the failure mode is the sink dropping into the cabinet with all that water. It is a same-week job, not a someday job, and re-supporting it properly is far cheaper than the water damage underneath.

Which benchtop problems can wait and which cannot?

Cannot wait: a loose undermount sink, black silicone at a splashback or wet area junction, and any crack that is visibly growing week to week. Those either get worse fast or cause damage beyond the benchtop. Can wait but should be booked: a small edge chip, a stalled hairline crack that has not moved in a year, a dull or etched patch on marble, and darkening around the tap on unsealed natural stone. Those are cosmetic or slow, and you can group them into one visit rather than paying a call-out for each.