How to Install a Bathroom Vanity: Step-by-Step Guide

Installing a bathroom vanity is a manageable DIY project for anyone comfortable with basic carpentry and plumbing. It typically takes 3–6 hours for a straightforward replacement. This guide walks through the complete process from removal to final finishing, with notes on the steps where most people run into trouble.

What Tools Do I Need to Install a Bathroom Vanity?

Gather these before you start — stopping mid-installation to hunt for a tool is how projects drag on.

Adjustable wrench and basin wrench
Pipe wrench or channel-lock pliers
Cordless drill with bits (including 1/4-inch and 3/8-inch)
Stud finder
Level (4-foot preferred)
Utility knife and putty knife
Caulk gun
Silicone caulk (100% silicone, not acrylic — bathroom grade)
Tape measure and pencil
Bucket, rags, and a towel
Safety glasses
Teflon tape (plumber's tape)
Hacksaw or PVC pipe cutter (if modifying drain)

Step 1: Turn Off the Water and Remove the Old Vanity

Shut off the hot and cold supply valves under the sink. If there are no local shut-offs, shut off the main water supply to the house. Turn on the faucet to release pressure and drain the lines. Place a bucket under the P-trap, then unscrew the slip nuts and remove the trap. Disconnect the supply lines from the faucet.

Remove the mirror or medicine cabinet above the vanity if applicable — this gives you room to work. Cut any caulk bead between the backsplash and wall with a utility knife. If the vanity is screwed to the wall through the inside back rail, remove those screws. The vanity should then lift or slide out. For heavier stone-top vanities, have a second person help — a 36-inch vanity with a stone top can weigh 150–200 lbs.

Step 2: Prepare the Wall and Floor

Once the old vanity is out, inspect the wall and floor. Look for:

Water damage or mould on the drywall behind the vanity. Any mould needs to be cut out and replaced with moisture-resistant drywall (greenboard or cement board) before proceeding.
The condition of the plumbing rough-in — check for corrosion on the shut-off valves. If they're older ball valves that feel stiff or are visibly corroded, this is the right time to replace them ($20 part, 30 minutes of work, or a quick call to a plumber).
Floor condition — if there's any soft spots or damaged subfloor where the vanity sat, repair it now.

Use a stud finder to locate and mark the wall studs behind the vanity installation area. You'll secure the vanity to at least one stud.

Step 3: Position and Level the Cabinet

Slide the new cabinet into position — leave the countertop off for now. Place your level on the top of the cabinet both front-to-back and side-to-side. Bathroom floors are almost never perfectly level. Use composite shims under the cabinet base to bring it level. Take your time here — a cabinet that's even 1/4 inch out of level will be noticeable once the countertop is on and the mirror is hung.

Once level, mark the stud locations on the back of the cabinet. Drill pilot holes through the cabinet's mounting rail (the horizontal rail running along the top inside back of the cabinet) and drive 2.5-inch or 3-inch screws into the studs. For floating/wall-mount vanities, follow the manufacturer's bracket instructions — this step is more involved and requires blocking in the wall if not already present.

Trim any shims flush to the cabinet base with a utility knife or oscillating tool.

Step 4: Mount the Countertop and Sink

If the sink is pre-mounted to the countertop (typical with complete sets from Modern Vanity), apply a continuous bead of 100% silicone caulk to the top edge of the cabinet, then carefully set the countertop in place. Press firmly to seat it. Wipe away any squeeze-out immediately with a damp cloth. Allow to cure for at least 2 hours before applying weight or water.

If your sink is a separate undermount that needs to be set into the countertop, this is done before placing the top on the cabinet: apply silicone to the rim of the sink cutout, set the sink, and secure with undermount clips. Let the silicone cure per the manufacturer's spec before proceeding.

Step 5: Connect the Faucet

Install the faucet on the countertop or sink before placing the top if possible — much easier to work on the counter at table height than reaching up under an installed unit. Secure the faucet mounting nut, connect the supply lines to the faucet tailpieces (hand-tight plus 1/4 turn), and attach the drain assembly (pop-up or grid drain) according to the faucet manufacturer's instructions.

Step 6: Connect the Drain Plumbing

This is where most DIYers slow down. The goal is to connect the drain tailpiece (the vertical pipe coming down from the sink drain) to the P-trap, and then to the wall drain stub-out.

The P-trap must maintain a water seal — the curved section of pipe holds water that blocks sewer gases from entering the bathroom.
Use the slip-joint nuts and washers included with the P-trap kit. Hand-tight plus one full turn is usually sufficient — overtightening plastic slip nuts causes cracks.
The drain must slope downward from the trap to the wall — never uphill or flat.
Turn the water back on slowly, fill the sink, and let it drain while you watch underneath for any leaks at every joint.

Step 7: Install the Backsplash

The backsplash fills the gap between the countertop and wall and protects the wall from water splatter. If your set includes a matching backsplash panel, apply a bead of silicone to the wall and to the countertop/backsplash joint, press the backsplash into place, and hold firm for a few minutes. Smooth the caulk joint with a wet finger. For tiled backsplashes, use tile adhesive and grout according to the tile manufacturer's instructions.

Step 8: Caulk the Perimeter and Finish

Run a thin, continuous bead of silicone caulk along all joints: where the countertop meets the wall, where the backsplash meets the wall, and where the cabinet meets the floor (if applicable). Smooth with a wet finger or caulk tool. Do not use paintable latex caulk in wet areas — it will mould within months. Use 100% silicone rated for bathroom use.

Reattach the cabinet doors and drawer fronts if they were removed for transport. Install the mirror or medicine cabinet above. Restore water flow, check for leaks one more time 24 hours later, and you're done.

For any questions about specific vanity models or installation requirements, visit our FAQ or see our full vanity collection for dimensions and spec sheets.