How To Seal a Kitchen Benchtop
What sealant should you use between a kitchen benchtop and the wall behind a cooktop?
For the joint between the benchtop and the wall, a wet-area silicone is the right family of product. Selleys No Mould Silicone Sealant is one Selleys names for it: it allows for ±25% joint movement, which more than compensates for the movement a kitchen joint sees, and it is formulated for humid and damp environments such as kitchens and bathrooms where mould is normally present.
Because the bench-to-wall joint is unlikely to be in direct contact with food, a wet-area silicone is suitable there. Where food contact may actually occur — preparing food directly on the benchtop surface, for example — the picture changes, and the section below sets out what the technical data sheets do and do not support.
What the technical data sheet publishes for No Mould
| Property | Selleys No Mould |
|---|---|
| Technology | Acetic cure silicone sealant, with Speed Seal technology |
| Skin time | 20 minutes |
| Curing rate | 2mm / 24 hours |
| Joint movement capability | ±25% (ISO 9047) |
| Elongation | Approximately 400% (ASTM D412 modified) |
| Packaging | 290mL cartridge; 100mL tube |
| Colours | Transparent, white |
| Waterproof / shower ready | 1 hour after application |
| Full cure | At least 48 hours, undisturbed |
| Service temperature | Not published on the technical data sheet |
Indicative data only, not intended for the preparation of specifications.
On the 150°C figure. Selleys' answer for this question refers to sealants that withstand temperatures up to 150°C. No Mould's technical data sheet does not publish a service temperature. The Selleys wet-area sealant whose data sheet does give that figure is Wet Area Matt Silicone, at −40°C to 150°C. Glass Silicone and Roof & Gutter Silicone also publish −60°C to +150°C, though neither is a kitchen benchtop product. If temperature resistance is the deciding factor for your joint, choose on the published figure rather than the general claim.
What ±25% means for a kitchen joint
A bench-to-wall joint is typically 3–6mm wide. At ±25% movement capability, a 5mm joint can absorb roughly 1.25mm of opening or closing without the bead tearing or letting go of either face.
That is comfortably more than a kitchen joint asks for. Benchtops move a little as the cabinetry settles and as the room heats and cools; walls move with the building. The failures you see in kitchen joints are almost never movement failures — they are adhesion failures caused by sealing onto a surface that was greasy, dusty or damp.
The cure rate is 2mm per 24 hours. A bead pressed 5mm into the joint therefore needs the better part of three days to cure through, even though the surface is watertight within the hour. Do not scrub the new bead or lean anything on it during that period.
Food contact — the honest position
This is worth being precise about, because it is a safety question rather than a performance one.
The wet-area silicone technical data sheets are explicit. No Mould is not suitable for food and drinking water contact. Wet Area Silicone and Wet Area Matt Silicone carry the same limitation. The Pro-Trade wet area sealant data sheet is not recommended for drinking water tanks either.
Across the Selleys sealant technical data sheets, there is no product documented as suitable for food contact surfaces. If you have a joint where food will be prepared directly on the surface across the sealed line, contact Selleys directly on 1300 555 205 and ask for a written recommendation for that specific application, rather than relying on a general kitchen sealant.
For the ordinary case — a bead between the back of the benchtop and the splashback or wall, where food is not prepared over the joint — the wet-area silicones are the products for the job.
How to seal the joint
- Remove any old sealant completely. Fresh silicone does not bond well to cured silicone, so a new bead over an old one fails along the seam.
- Clean the surfaces with turps and let them dry thoroughly. Kitchen joints collect cooking oil film, which is the most common reason a bead lifts.
- Where the old bead was mouldy, spray the gap with Selleys Rapid Mould Killer first — that is the first step in No Mould's own directions — then rinse and dry.
- Cut the nozzle at 45 degrees and size the opening to the joint width. Smaller than you think; you can always widen it.
- Gun the sealant in with steady pressure, pushing it into the joint rather than laying it across the top.
- Tool with a spatula dipped in detergent water within 10 minutes of application.
- Clean up with turps before the product skins.
- Leave it undisturbed — at least 48 hours for full cure with No Mould.
Limitations — where these sealants should not be used
- Not suitable for food or drinking water contact.
- Not paintable. Complete painting seven days before applying the sealant.
- Not suitable for aquariums or for permanent water immersion.
- Not suitable for metals other than aluminium and stainless steel (No Mould), and not for PE, PP or PTFE plastics.
- Acetic cure and stone. No Mould is an acetic cure silicone. Where the benchtop is natural or engineered stone, Selleys' guidance is a neutral cure silicone — Wet Area Silicone or Wet Area Matt Silicone — because neutral cure products do not release acetic acid as they set.
- Keep the bead clean. No Mould's mould resistance is stated on the condition that soap scum and dirt are regularly cleaned off, since that residue is what feeds mould growth.
Safety: a cooktop is an ignition source at bench height
No Mould carries the signal word Warning, with eye irritation Category 2A (H319, causes serious eye irritation), skin irritation Category 2, and skin sensitisation Category 1. Wet Area Silicone, the neutral-cure alternative this page recommends for stone, carries Warning with H319 and H317, may cause an allergic skin reaction.
H317 is not irritation, and step 6 is where it is earned. Sensitisation is the immune system learning to react to the material: permanent once acquired, then triggered by far smaller exposures, and built by repeated casual contact. Use the detergent-dipped spatula the step describes rather than a bare finger. Cured silicone is inert.
Steps 1 and 2 are the ones that bring a flammable liquid onto a bench beside a flame. Removing the old bead means Selleys Sealant Remover: classified Danger, Poison Schedule S5, over 60% petroleum naphtha, carrying H304 (may be fatal if swallowed and enters airways), H226 (flammable liquid and vapour — Dangerous Goods Class 3, UN 1133, Packing Group II), H336 (may cause drowsiness or dizziness) and H315. Step 2's turps wipe-down is a flammable solvent as well.
This page's joint runs behind a cooktop. A gas burner or a standing pilot is at the same height as the bead you are stripping and often within arm's reach of it. A Packing Group II flammable liquid a few hundred millimetres from a naked flame is not a theoretical risk. Isolate the cooktop before you start — gas off at the wall, or the appliance off at its switch — and do not relight until the solvent has gone and the kitchen has been aired.
H336 in a galley kitchen is a predictable outcome, not a warning label. A long bench-to-wall joint, a 5mm layer left ten minutes, and a second application on stubborn residue, in a room with the door shut, is enough to produce it. Open the windows, run the rangehood, and step out between applications.
H304 matters because of where the tub sits. An open 375g tub of light beige paste on a food preparation surface looks like filler and is at child height on a benchtop. Lid on between applications, out of reach, never decanted into another container. If any is swallowed, do not induce vomiting — rinse the mouth, give a glass of water and seek medical advice immediately.
The food-contact question the section above sets out is a separate matter and the position does not change: no Selleys sealant is documented as suitable for food contact surfaces. Lower-hazard route for the strip: cut and scrape the bulk out first — the remover is designed for a residual film under 5mm.
Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand.
Common questions about sealing a kitchen benchtop
Which colour should I use?
No Mould's data sheet lists transparent and white. Clear disappears into most joints; white suits a white splashback or a painted wall.
Is No Mould right for a stone benchtop?
For natural or engineered stone, use a neutral cure product instead. Neutral cure is Selleys' recommendation for granite, marble and engineered stone — see silicone between a glass splashback and a Caesarstone benchtop.
How soon can I use the kitchen again?
No Mould is waterproof one hour after application. It needs at least 48 hours undisturbed to reach full cure, and the cure works through the bead at 2mm per 24 hours.
Can I paint over the bead to match the wall?
No. These silicones are not paintable — do the painting first and seal at least seven days afterwards.
What about the joint right around the cooktop itself?
That is a hotter joint and a different question — see replacing perished silicone between a cooktop and a stone benchtop.
Will it stick to laminate?
Wet Area Silicone lists plastic laminates among its suitable materials, along with ceramic, glazed and porcelain fixtures, metal, aluminium, rubber, glass, stainless steel and concrete.
How do I stop it going mouldy?
Clean the bead regularly. Soap scum, food residue and grease are what mould feeds on; the silicone itself is not the food source.
Can I put a second bead over the first to tidy it up?
No — cut it out and start again. Silicone does not bond reliably to cured silicone.
What clean-up do I need on hand?
Mineral turpentine for uncured product. Once cured it has to come off with Selleys Sealant Remover or by cutting and scraping.
Which colour should I use?
No Mould's data sheet lists transparent and white. Clear disappears into most joints; white suits a white splashback or a painted wall.
Is No Mould right for a stone benchtop?
For natural or engineered stone, use a neutral cure product instead. Neutral cure is Selleys' recommendation for granite, marble and engineered stone — see silicone between a glass splashback and a Caesarstone benchtop .
How soon can I use the kitchen again?
No Mould is waterproof one hour after application. It needs at least 48 hours undisturbed to reach full cure, and the cure works through the bead at 2mm per 24 hours.
Can I paint over the bead to match the wall?
No. These silicones are not paintable — do the painting first and seal at least seven days afterwards.
What about the joint right around the cooktop itself?
That is a hotter joint and a different question — see replacing perished silicone between a cooktop and a stone benchtop .
Will it stick to laminate?
Wet Area Silicone lists plastic laminates among its suitable materials, along with ceramic, glazed and porcelain fixtures, metal, aluminium, rubber, glass, stainless steel and concrete.
How do I stop it going mouldy?
Clean the bead regularly. Soap scum, food residue and grease are what mould feeds on; the silicone itself is not the food source.
Can I put a second bead over the first to tidy it up?
No — cut it out and start again. Silicone does not bond reliably to cured silicone.
What clean-up do I need on hand?
Mineral turpentine for uncured product. Once cured it has to come off with Selleys Sealant Remover or by cutting and scraping.