A bathroom vanity is the cabinet that supports the sink, stores toiletries, and provides counter space. Replacing or installing one combines cabinet mounting, plumbing, and finishing — a moderately complex DIY but achievable for confident installers. Wall-mount vanities (floating) and freestanding cabinets follow similar plumbing but different mounting.
This guide covers a standard freestanding bathroom vanity replacement (existing vanity coming out, new one going in).
- Skill level
- Advanced
- Time
- 4–8 hr
- Steps
- 10
- Tools
- 9, listed below
- Materials
- 7, listed below
Before you start
Three things to settle:
1. Vanity dimensions and plumbing alignment. New vanity must align with existing plumbing rough-ins (water supply, drain). Most vanities have access panels in the back; verify plumbing fits within. Drain typically needs to be at 16-20 inches above floor; supplies at 22-24 inches.
2. Wall-mount vs freestanding. Freestanding: most common, sits on the floor. Wall-mount (floating): mounted to wall studs, more modern, requires accurate stud-anchoring at the right height. Pick based on style preference and wall structure.
3. Top sold separately or combined. Some vanities come with integrated tops; others require purchasing tops separately. Verify scope before installation. Top installation is a separate step on top of the cabinet base.
What you'll need
Tools
- Adjustable wrench
- Slip-joint pliers
- Phillips screwdriver
- Level (4-foot)
- Stud finder
- Drill with bits
- Caulking gun
- Bucket and old towels
- Tape measure
Materials
- New bathroom vanity (cabinet)
- Vanity top (if separate)
- Sink faucet (often included)
- 100% silicone caulk
- Wood screws #8 × 2-1/2 inch (for wall-mount or anchoring)
- Plumber's putty
- Painter's tape
Plumbing rough-in must match
If existing plumbing rough-in is in different location than the new vanity needs, you'll have to relocate plumbing — significant additional work requiring permits in Ontario.
Verify alignment before purchasing a specific vanity. Most stock vanities work with standard plumbing; specialty vanities may not.
Step-by-step instructions
Disconnect existing vanity
Shut off water supply at the bathroom (or main).
Disconnect supply lines from sink faucet. Disconnect drain P-trap.
If existing vanity has a top, lift it off the cabinet (it's usually only secured by silicone seal — break the seal carefully).
Remove the cabinet — typically held by 2-4 screws into the wall.
Inspect the wall behind
Check for water damage, mould, or other issues.
Repair drywall if needed before installing new vanity.
Position new vanity cabinet
Lift cabinet into position. Align with plumbing rough-ins through the vanity's back access panel.
Verify cabinet sits flush with the wall and is level (front to back, side to side). Shim under feet if needed.
Anchor cabinet to wall
For freestanding: drive #8 × 2-1/2 inch wood screws through the cabinet's mounting rail (typically a heavy strip across the top back) into wall studs. 2-3 screws minimum.
For wall-mount/floating: critical to mount into studs OR use rated wall anchors. Floating vanities depend entirely on wall anchoring.
Install vanity top (if separate)
Apply silicone bead around the top of the cabinet.
Lower the top onto the cabinet, aligned with the cabinet's edges.
Press to seat the silicone.
Install faucet on top
Per faucet's instructions. Most bathroom faucets have 4-inch centerset configuration.
Apply plumber's putty around the faucet's base before mounting.
Install drain assembly
Apply plumber's putty under drain flange. Drop into the sink's drain hole.
From below the sink, install drain body components and tighten the locking nut.
Connect plumbing
Connect supply lines from shut-off valves to faucet (Teflon tape on threads).
Connect P-trap from drain to wall plumbing.
Hand-tighten plus a quarter to half turn.
Caulk seams
Where vanity meets the wall: silicone caulk seal.
Where top meets the wall (if backsplash): silicone caulk.
Where faucet meets top: ensure proper seal per faucet's install.
Restore water and test
Open shut-off valves slowly.
Test faucet — flow, hot/cold sides, no leaks.
Drain test — fill sink, drain it, verify P-trap doesn't leak.
Wait 24 hours and re-check for slow leaks.
Common mistakes that cost you
- Plumbing rough-in mismatch. New vanity plumbing has to align with existing. Verify before installing.
- Not anchoring to wall. Vanity tips forward when drawers extended. Always anchor.
- Skipping silicone seal. Water gets behind the vanity over years. Seal vanity-to-wall joint.
- Wrong drain alignment. Drain doesn't connect cleanly to wall plumbing. Verify alignment with rough-in.
- Over-tightening top to cabinet. Cracks the top. Silicone seal does the work; minimal mechanical fastening.
Frequently asked questions
Can I install a vanity over existing plumbing?
Yes, if the new vanity's plumbing access aligns with the existing rough-in.
Check alignment before purchasing. Standard vanities work with standard plumbing locations.
Wall-mount or freestanding?
Wall-mount (floating): modern look, easier floor cleaning, requires careful stud anchoring.
Freestanding: traditional, more storage space, no special wall requirements.
Match style to bathroom aesthetic.
How do I anchor a new bathroom vanity to the wall?
A freestanding vanity is anchored with #8 x 2-1/2 inch wood screws driven through the mounting rail at the top back into wall studs, 2 to 3 screws minimum. Without anchoring, the vanity tips forward when drawers are pulled out.
A wall-mount or floating vanity depends entirely on its wall anchoring, so it must go into studs or use rated wall anchors. Level the cabinet first, shimming under the feet if needed.
How should a vanity top be attached to the cabinet?
A separate vanity top sits on a bead of silicone run around the top of the cabinet. Lower the top on, align it with the cabinet edges and press down to seat the silicone. The silicone does the work, with minimal mechanical fastening, because over-tightening a top to the cabinet can crack it.
Where the vanity and top meet the wall or backsplash, a silicone caulk seal keeps water from getting behind the vanity.
How do I test a new bathroom vanity for leaks?
A new vanity is leak tested by opening the shut-off valves slowly, running the faucet on both hot and cold, and checking every supply connection. For the drain, fill the sink, let it drain, and confirm the P-trap does not leak. Wait 24 hours and check again for slow leaks. Supply lines take Teflon tape on the threads, and connections go hand-tight plus a quarter to half turn.
When to call us instead
If your bathroom plumbing needs reroute or your wall structure requires reinforcement for floating vanity, professional installation simplifies the work.
Book a free 60-minute site visit →Dream Touch Renovations · 33 Roydon Pl, Suite 210, Ottawa, ON K2E 1A3 · (613) 862-4555
Renovating homes across Ottawa, Kanata, Nepean, Barrhaven, Orléans and Stittsville.
Related Ottawa services
If you're refreshing a bathroom, our bathroom renovation team handles vanity, plumbing, and tile as fixed-price work. Book a free 60-minute consultation.
Official references
- Do I need a building permit?, City of Ottawa
- O. Reg. 163/24: Building Code, Government of Ontario