How To Install a Bathroom Vanity
How do you install a bathroom vanity?
A new vanity is one of the highest-impact changes you can make to a bathroom, and most of the work is within reach as a DIY job. The sequence is: have a plumber disconnect the old unit, strip the old sealant, find and mark the studs, cut the pipe holes, level and screw the cabinet to the studs, bed the sink base on silicone, have a plumber reconnect, then seal the gap between the sink base and the wall.
Two parts of that are not DIY. A plumber disconnects the old plumbing at the start, and a licensed plumber connects the water pipes and tapware at the end. Everything between those is yours.
The adhesive decision is simple: Selleys Wet Area Silicone does two separate jobs here — it beds the sink base onto the cabinet, and it seals the gap between the sink base and the wall.
What you will need
- Selleys Wet Area Silicone — select the colour that best suits your vanity top
- A caulking gun
- Your chosen bathroom vanity and tapware
- Selleys Sealant Remover
- Mineral turpentine and methylated spirits
- A stud finder
- A hole saw
- A cordless drill
- A spirit level
- A blade or knife
- A silicone scraper or spatula
- A soft clean cloth
Step 1 — Remove the old vanity
After a plumber has disconnected the plumbing, remove the old vanity from the wall and dislodge any remaining sealant with the scraper. Selleys Sealant Remover will help.
Its method: cut the old sealant back to a thin layer less than 5 mm deep, spread at least a 5 mm thick layer of remover evenly over what is left, leave it at least 10 minutes, then scrape it off with a scraper or sealant remover tool. Clean residue and tools immediately with mineral turpentine. It is suitable for use on ceramic tiles, porcelain, glass, grout, most metals, laminate, masonry, coated timber and most painted surfaces — but not on rubber, EPDM or polycarbonate, and it should be tested for compatibility before use.
Get the wall genuinely clean at this stage. Any silicone film left behind will stop the new bead bonding, and it is far easier to deal with now than when the new cabinet is in the way.
Step 2 — Find the studs and cut the pipe holes
Use the stud finder to locate and clearly mark your timber wall studs. These will be used to fix and stabilise the vanity unit later on.
Carefully mark and cut the pipe holes into the back of the vanity using the hole saw. These are for the water outlets. Measure from a fixed reference — a wall corner or the floor — rather than from the old cabinet, and cut slightly generously; a hole that is a few millimetres oversize is invisible behind the cabinet, while one that is a few millimetres out of position is a problem.
Step 3 — Position and level
Move the vanity unit into position, using the spirit level to ensure it is flush.
Check level in both directions and check the front face for plumb. Bathroom floors are rarely flat, and packing the base now is much easier than discovering a slope after the top is bedded on.
Step 4 — Fix it to the studs
Drill into the timber wall studs and attach cabinet screws. These need to be at both the top and bottom of the vanity unit to ensure it is secure.
Top and bottom is the instruction that matters. Fixing only at the top lets the base kick out when weight goes on the front edge of the top.
Step 5 — Assemble the tapware
Assemble your tapware according to the manufacturer's instructions before fixing it to your vanity unit. Your plumber can assist with this part.
Doing this before the top goes on is much easier than reaching up under a fitted basin afterwards.
Step 6 — Bed the sink base on silicone
Use your Selleys Wet Area Silicone to steadily apply a thin bead of silicone all the way around the top edge of the cabinet.
Before you start, extrude a small amount onto a piece of scrap material to make sure you have a smooth continuous flow of sealant. Clean and dry the surfaces of oil, dirt and grease with turps and then methylated spirits, and allow to dry completely before applying silicone.
Step 7 — Place the top
Place your sink base on top of the cabinet, slide it against the wall and press it firmly into place so the silicone sets in the right position. Allow it to set for a few hours.
This is where silicone earns its place over a rigid adhesive. Using silicone to fix the vanity top onto the cabinet allows wiggle room — you can nudge the top square while the bead is still soft. Once it is completely dry, it will not move.
The bead holds the top in position within a few hours, but it has not reached full strength then. Wet Area Silicone's technical data sheet gives a cure of 72 hours, and that is the figure to use for anything load bearing or watertight. Setting for a few hours is enough to proceed with the plumbing; it is not the same as cured.
Step 8 — Plumbing connection
Once completely set, have a licensed plumber connect the water pipes and tapware.
Step 9 — Seal the gap to the wall
To protect the cabinet from water damage you need to seal the gap between the sink base and the wall. Use a clean cloth to wipe down any excess dust from the area, making sure it is completely dry, then apply a thick, even bead of Selleys Wet Area Silicone to the gap.
Tool it within 5 to 10 minutes with a spatula dipped in detergent and water. Push the sealant into the gap rather than laying it across the surface — depth of bond is what lets the bead survive the small movements between a cabinet and a wall. Clean up with turps before the product skins.
Wet Area Silicone specifications
| Property | Typical result |
|---|---|
| Technology | Neutral cure, 100% silicone sealant |
| Packaging | 420 g cartridge |
| Shore A hardness | 30 |
| Elongation at break | 450% (ASTM D412) |
| Service temperature | −40 °C to +150 °C |
| Tooling window | 5–10 minutes from application |
| Cure | 72 hours |
| VOC content | <50 g/L |
Indicative data only, not intended for the preparation of specifications. Its published substrates include ceramic, glazed and porcelain fixtures, metal, copper and brass fittings, powder coated aluminium, aluminium, plastic laminates, rubber, glass, stainless steel and concrete — which covers most vanity tops and cabinet materials. It carries a 25 year guarantee against cracking and peeling when used as directed for private use within 12 months of purchase.
Why neutral cure suits this job
Wet Area Silicone is a neutral cure product, meaning it does not release acetic acid as it sets. That matters when the top is stone, or when the bead sits against brass or copper tapware and powder coated metal — all of which are on its substrate list. If your vanity top is natural or engineered stone, neutral cure is the right choice and an acetic cure product is not.
Limitations
- Not paintable. Complete any painting 7 days before applying the sealant — worth planning if the bathroom wall is being repainted as part of the same job.
- Not suitable for use on PP, PE or PTFE.
- Not suitable for aquariums, or for food or drinking water contact.
- Not suitable for permanent water immersion.
- Store below 30 °C in a dry place, and use within 6 months of opening.
- Plumbing connections are for a licensed plumber. Both the disconnection at the start and the connection at the end are named as plumber's work in this guide.
Safety: the bathroom is the smallest room in the house, and step 1 fills it with solvent
Wet Area Silicone is a Warning-level product — skin sensitisation, eye irritation and a combustible-liquid classification. The item on the tool list that needs planning for is the remover.
Selleys Sealant Remover is classified Danger and is Poison Schedule S5: H304 (may be fatal if swallowed and enters airways), H226 (flammable liquid and vapour), H336 (may cause drowsiness or dizziness) and H315 (causes skin irritation). Dangerous Goods Class 3, UN 1133, Packing Group II.
The dwell time is what makes the vapour load. Most solvent jobs are a wipe: a cloth, a few seconds, gone. This one is different by design — spread at least a 5 mm layer over the old bead and leave it a minimum of 10 minutes. That is a wide, open, evaporating surface sitting still, in a room that is typically two or three cubic metres with the door half blocked by a vanity you are trying to remove. Then step 6 adds mineral turpentine and methylated spirits to the same room. Open the window, run the exhaust fan for the whole job, and leave the room while the remover dwells rather than kneeling over it.
H226 in a bathroom means checking for one specific thing: an instantaneous gas hot water unit, a gas heater or a pilot light in or adjoining the room. Vapour is denser than air and travels along the floor. Isolate anything with a flame before you start, and do not run a portable fan heater to dry the area.
H304 is why the tub is never decanted into a cup or a bottle, and why the product's own first aid says do not induce vomiting if any is swallowed. H315 is why gloves are specified — nitrile, not household rubber — and safety glasses matter because you scrape back toward your own face at wall height.
Reduce how much you need. Step 1 already says to dislodge what you can with the scraper first. Every millimetre of old bead you cut away mechanically is remover you do not have to spread, dwell and breathe.
Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand. Plumbing connections remain a licensed plumber's work, as this guide says at both ends.
Common questions about installing a bathroom vanity
Do I need a plumber?
Yes, at both ends — to disconnect the old plumbing before you start, and to connect the water pipes and tapware once the unit is set. The connection must be done by a licensed plumber.
Why silicone rather than a construction adhesive for the top?
Because silicone gives you wiggle room. It lets you slide the top square while it is still soft, and once dry it holds position.
How long before I can use the vanity?
The bead sets in position within a few hours, which is enough to proceed with the plumbing. Wet Area Silicone's full cure is 72 hours.
How do I get the old sealant off the wall?
Scrape it back, then use Selleys Sealant Remover — at least a 5 mm thick layer over sealant already cut back to under 5 mm, left at least 10 minutes, then scraped off and cleaned up with mineral turpentine.
How do I clean the surfaces before sealing?
Turps first, then methylated spirits, and let it dry completely. Turps lifts oils and silicone residue; metho carries off what is left and evaporates without a film.
Where exactly do the fixing screws go?
Into the timber wall studs, at both the top and the bottom of the unit.
How long do I have to smooth the bead?
Five to ten minutes, with a spatula dipped in detergent and water.
What if my vanity top is stone?
Wet Area Silicone is a neutral cure product, which is the correct choice for stone. Check your benchtop supplier's own guidance as well, since stone brands are not listed by name on Selleys data sheets.
Can I paint the sealed joint?
No. Wet Area Silicone is not paintable — painting has to be completed 7 days beforehand.
What if there is no stud where I need one?
This guide's method fixes into timber studs. If your wall framing does not line up with the cabinet, that is a question for a builder or the vanity supplier rather than a job for adhesive.
Is there a guide for sealing the basin itself?
Yes — how to seal a sink.
Do I need a plumber?
Yes, at both ends — to disconnect the old plumbing before you start, and to connect the water pipes and tapware once the unit is set. The connection must be done by a licensed plumber.
Why silicone rather than a construction adhesive for the top?
Because silicone gives you wiggle room. It lets you slide the top square while it is still soft, and once dry it holds position.
How long before I can use the vanity?
The bead sets in position within a few hours, which is enough to proceed with the plumbing. Wet Area Silicone's full cure is 72 hours.
How do I get the old sealant off the wall?
Scrape it back, then use Selleys Sealant Remover — at least a 5 mm thick layer over sealant already cut back to under 5 mm, left at least 10 minutes, then scraped off and cleaned up with mineral turpentine.
How do I clean the surfaces before sealing?
Turps first, then methylated spirits, and let it dry completely. Turps lifts oils and silicone residue; metho carries off what is left and evaporates without a film.
Where exactly do the fixing screws go?
Into the timber wall studs, at both the top and the bottom of the unit.
How long do I have to smooth the bead?
Five to ten minutes, with a spatula dipped in detergent and water.
What if my vanity top is stone?
Wet Area Silicone is a neutral cure product, which is the correct choice for stone. Check your benchtop supplier's own guidance as well, since stone brands are not listed by name on Selleys data sheets.
Can I paint the sealed joint?
No. Wet Area Silicone is not paintable — painting has to be completed 7 days beforehand.
What if there is no stud where I need one?
This guide's method fixes into timber studs. If your wall framing does not line up with the cabinet, that is a question for a builder or the vanity supplier rather than a job for adhesive.
Is there a guide for sealing the basin itself?
Yes — how to seal a sink .