How To Fill Gaps in a Granite Benchtop
What can you use to fill a small gap in a granite benchtop join?
Two pieces of advice, in order of importance.
First, contact the installer. Stone fabricators work with colour-matched, stone-specific jointing compounds, and if your benchtop has just been fitted, the person who fitted it may have exactly the right product for that stone and that join. That is the recommendation Selleys makes first, and it is worth acting on before you reach for anything else.
Second, if you are filling it yourself, use a 100% silicone product such as Selleys Wet Area Silicone. It comes in a range of colours, so you can pick the one closest to the stone.
Why a silicone rather than a rigid filler
A benchtop join is not a static crack. The bench sits on cabinetry that moves slightly with load and humidity, and the join between two slabs opens and closes fractionally with that. A rigid filler in that line will craze. A silicone stays elastic and keeps the join sealed against the water and food debris that would otherwise work into the gap.
The other reason is chemistry. Wet Area Silicone is a neutral cure silicone — it cures without releasing acetic acid. Acid-cure (acetic) silicones give off acetic acid as they cure, which is the sharp vinegar smell you get for the first day, and neutral cure is the safer choice around stone and other sensitive substrates.
Colour matching
Wet Area Silicone is available in a 300g cartridge in Clear, Black, Dark Grey, Light Grey, Off White, White and Ivory, with TwinPack and TriplePack options in white. On a granite join, clear or the closest grey is usually the least visible. It is worth running a test bead on an offcut or in a hidden spot before you commit to a colour — silicone reads darker in a narrow joint than it does out of the cartridge.
The limitation you must know before you seal a kitchen bench
The Wet Area Silicone technical data sheet lists among its limitations: not suitable for food or drinking water contact. A kitchen benchtop is a food preparation surface, so this is a real constraint, not a formality.
In practice that means: seal the join, tool it flush so there is no raised bead collecting food, and do not treat the sealant as a food-contact surface. If the join runs through the area where you cut and prepare food directly on the stone, this is another reason to go back to the stone fabricator for a jointing compound intended for that use.
The other limitations are:
- Not paintable. Complete any painting seven days before applying the sealant.
- Not suitable for use on PP, PE or PTFE.
- Not suitable for aquariums.
- Not suitable for permanent water immersion.
The published figures
| Technology | Neutral cure silicone, 100% silicone |
| Packaging | 300g cartridge |
| Colours | Clear, Black, Dark Grey, Light Grey, Off White, White, Ivory |
| Skin time | 5 to 10 minutes (25°C, 50% RH) |
| Tooling window | Within 5 to 10 minutes of application |
| Cure rate | Approximately 2mm per 24 hours (23°C, 50% RH) |
| Full cure | 72 hours |
| Guarantee | 25 years against cracking and peeling, when used as directed for private use and within 12 months of purchase |
Indicative data only, not intended for the preparation of specifications.
The 5 to 10 minute tooling window is short, and it is the figure that catches people out on a benchtop. Once the surface starts to skin, tooling tears it rather than smoothing it, and on a highly visible stone join a torn bead has to be cut out and redone. Work in short lengths and tool as you go rather than running the whole join first.
How to fill the join
- Clean the join so both faces are free of dirt, grease, oil and water. Clean the stone with turps and let it dry completely.
- Cut the nozzle at a 45° angle to a width slightly narrower than the gap, cut the cartridge tip and fit the nozzle.
- Mask both sides of the join with tape if you want a crisp line. On stone this is worth doing.
- Load a caulking gun and apply with steady pressure, pushing the sealant into the joint rather than laying it across the top.
- Tool with a spatula dipped in detergent water within 5 to 10 minutes, leaving the bead flush rather than proud.
- Remove the masking tape before the sealant skins.
- Clean up with turps before the product skins. Cured silicone has to be cut and scraped off, or removed with Selleys Sealant Remover.
- Leave it undisturbed. Cure runs at about 2mm per 24 hours, with full cure at 72 hours.
Safety: step 7 brings a Danger-classified solvent onto the bench
Wet Area Silicone, the product recommended here, carries the signal word Warning: H319, causes serious eye irritation (Category 2A), and H317, may cause an allergic skin reaction (skin sensitisation Category 1). H317 is skin sensitisation, not irritation: permanent once acquired, then triggered by far smaller exposures, and built by repeated casual contact. Step 5 above is right for more than one reason — tool with the detergent-dipped spatula, not a bare finger.
The serious classification on this page belongs to the removal product in step 7. Selleys Sealant Remover is classified Danger, Poison Schedule S5, and is over 60% petroleum naphtha — a thickened hydrocarbon solvent:
- H304 — may be fatal if swallowed and enters airways (aspiration hazard, Category 1)
- H226 — flammable liquid and vapour; Dangerous Goods Class 3, UN 1133, Packing Group II
- H336 — may cause drowsiness or dizziness
- H315 — causes skin irritation
A kitchen benchtop is a flammable-liquid job carried out next to a naked flame. Packing Group II is the middle rung of Class 3, and a granite join usually runs within a metre or two of a cooktop. Turn the gas off at the wall before any solvent comes out, and do not relight until the room has been aired. The turps in step 1 and for clean-up is a flammable solvent too.
H336 is what a closed galley kitchen produces. The method is a layer at least 5mm thick left at least ten minutes, with a second application on stubborn residue. Open the windows, and step out between applications rather than standing over it.
H304 matters here because of where the tub sits. It is a light beige paste in a 375g screw-top tub, left open on a food preparation surface, and it looks like filler. Put the lid back on between applications, keep it out of reach of children, and never decant it into another container. If any is swallowed, do not induce vomiting — that is the mechanism that gets a hydrocarbon into the lungs. Rinse the mouth, give a glass of water and seek medical advice immediately.
The lower-hazard route: cut and scrape the bulk of the old bead away first. The remover is designed to soften a residual film under 5mm, so the more you remove mechanically, the less solvent the kitchen has to take. Gloves and eye protection for both parts of the job — you are scraping toward yourself at bench height.
Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand.
Common questions
Should I call the installer first?
Yes. Selleys strongly recommends contacting the installer to confirm whether they have a product designed specifically for that type of join.
Why 100% silicone rather than a filler?
Because the join moves and gets wet. A rigid filler will crack; a silicone stays flexible and keeps the joint sealed.
What colours can I get?
Clear, Black, Dark Grey, Light Grey, Off White, White and Ivory, in 300g cartridges.
Is it safe for a food preparation surface?
The data sheet states it is not suitable for food or drinking water contact. Tool it flush, keep it out of the direct food preparation area, and consider a stone-specific jointing product from the fabricator if the join runs through where you cut food.
Can I paint over it to match the stone?
No. It is not paintable — painting has to be completed seven days before the sealant is applied.
How long do I have to tool the bead?
5 to 10 minutes. After that the surface skins and tooling will tear it.
How long until it is fully cured?
72 hours, curing at about 2mm per 24 hours.
Will it stick to granite?
Its listed substrates include ceramic, glazed and porcelain fixtures, metal, copper and brass fittings, powder coated aluminium, aluminium, plastic laminates, rubber, glass, stainless steel and concrete. For an unusual or sealed stone, test in an inconspicuous spot first.
What if the gap is in a wet area of the bench, near the sink?
Wet Area Silicone is designed for exactly that environment — showers, baths, spas, plumbing fixtures and sinks — but it is still not for permanent water immersion.
Is there a guide to sealing a benchtop?
Yes — how to seal a kitchen benchtop covers the wider job.
Should I call the installer first?
Yes. Selleys strongly recommends contacting the installer to confirm whether they have a product designed specifically for that type of join.
Why 100% silicone rather than a filler?
Because the join moves and gets wet. A rigid filler will crack; a silicone stays flexible and keeps the joint sealed.
What colours can I get?
Clear, Black, Dark Grey, Light Grey, Off White, White and Ivory, in 300g cartridges.
Is it safe for a food preparation surface?
The data sheet states it is not suitable for food or drinking water contact. Tool it flush, keep it out of the direct food preparation area, and consider a stone-specific jointing product from the fabricator if the join runs through where you cut food.
Can I paint over it to match the stone?
No. It is not paintable — painting has to be completed seven days before the sealant is applied.
How long do I have to tool the bead?
5 to 10 minutes. After that the surface skins and tooling will tear it.
How long until it is fully cured?
72 hours, curing at about 2mm per 24 hours.
Will it stick to granite?
Its listed substrates include ceramic, glazed and porcelain fixtures, metal, copper and brass fittings, powder coated aluminium, aluminium, plastic laminates, rubber, glass, stainless steel and concrete. For an unusual or sealed stone, test in an inconspicuous spot first.
What if the gap is in a wet area of the bench, near the sink?
Wet Area Silicone is designed for exactly that environment — showers, baths, spas, plumbing fixtures and sinks — but it is still not for permanent water immersion.
Is there a guide to sealing a benchtop?
Yes — how to seal a kitchen benchtop covers the wider job.