Building a floating timber vanity cabinet is a satisfying DIY project that can transform your bathroom. With careful planning, the right materials, and attention to waterproofing, a competent home handyperson can achieve a professional-looking result. That said, any plumbing connections must be handled by a licensed tradesperson — more on that below.
Planning Your Vanity Cabinet
Before picking up a saw, measure your bathroom carefully. Consider the width of your basin, the height that suits the users (typically 850–900 mm from floor to top of basin is comfortable for adults), and how much depth you need (usually 450–500 mm). Sketch a simple plan showing the carcass (box), any doors or drawers, and where the basin will sit.
Check whether your project needs a building consent. A straightforward vanity cabinet replacement generally won't require one, but if you're moving plumbing or making structural changes, check with your local council. The MBIE Building Performance website has clear guidance on Schedule 1 exemptions.
Choosing the Right Timber and Materials
Bathrooms are wet, humid environments, so material choice is critical.
- Plywood (moisture-resistant grade): The best choice for the carcass. Look for moisture-resistant (MR) or marine-grade plywood at your local Bunnings or Mitre 10. Standard 18 mm thickness works well for shelves and sides.
- Solid timber for faces and doors: Hardwoods like oak, rimu, or macrocarpa look great and handle moisture better than softwoods. Avoid untreated pine in wet zones.
- MDF: Only use moisture-resistant MDF (green core) if at all, and keep it well away from direct water contact.
- Hardware: Stainless steel or brass screws and hinges resist corrosion. Soft-close hinges are worth the extra cost.
For sheet materials and timber, PlaceMakers is a reliable NZ trade supplier with good stock of moisture-resistant products.
Tools You'll Need
- Tape measure, pencil, and square
- Circular saw or table saw
- Jigsaw (for basin cutout)
- Drill/driver and bits
- Spirit level
- Stud finder
- Clamps
- Router (optional, for clean edges)
- Sandpaper (80, 120, 180 grit)
Step-by-Step Build Process
1. Cut Your Carcass Panels
Cut the top, bottom, two sides, and a back panel from your moisture-resistant plywood. The back panel can be thinner (9–12 mm). Label each piece clearly.
2. Assemble the Box
Pre-drill and countersink all screw holes to prevent splitting. Glue and screw the sides to the top and bottom panels using a waterproof PVA or construction adhesive. Attach the back panel to square up the carcass and add rigidity. Check for square by measuring diagonals — they should be equal.
3. Make and Fit Doors or Drawers
Cut door panels from your chosen timber or plywood. Sand edges smooth. Fit concealed hinges or drawer runners according to the manufacturer's instructions. Leave a consistent 2–3 mm gap around doors for movement.
4. Sand and Finish
Sand all surfaces progressively through the grits. Apply a waterproof finish suitable for wet areas — this is essential. Two-pack polyurethane or a quality water-based bathroom enamel from Resene or Dulux are good options. Apply at least two coats, sanding lightly between coats. Pay special attention to end grain, which absorbs moisture readily.
5. Wall Fixing — The Most Important Step
A floating vanity must be fixed securely to wall studs or a solid noggin. Use a stud finder to locate studs (typically at 600 mm centres in NZ timber-framed homes built to NZS 3604). Fix a French cleat (a pair of interlocking bevelled timber strips) or heavy-duty metal brackets to the studs at the correct height. The cabinet then hangs on the cleat. Use 75 mm structural screws into studs — never rely on plasterboard anchors alone for a loaded cabinet.
| Fixing method | Suitable for | Notes |
|---|---|---|
| French cleat | Most timber-framed walls | Strong, adjustable, easy to level |
| Metal wall brackets | Concrete/block walls | Use masonry anchors |
| Timber noggin + screws | New builds or renos | Requires access inside wall |
6. Basin Cutout and Sealing
If fitting an undermount or drop-in basin, mark and cut the opening with a jigsaw. Seal all cut edges with waterproof sealant or extra coats of finish before fitting the basin. Apply a bead of silicone sealant (bathroom-grade, mould-resistant) around the basin perimeter once installed.
Waterproofing and the NZ Building Code
Bathrooms are classified as wet areas under the NZ Building Code (Clause E3 — Internal Moisture). While a vanity cabinet itself doesn't require waterproof membrane treatment, the wall and floor surfaces behind and beneath it must comply with E3 requirements. If you're tiling or lining behind the vanity, ensure the substrate and waterproofing are done correctly. BRANZ publishes excellent guidance on wet area construction.
When to Call a Professional
Plumbing connections are restricted work under the Plumbers, Gasfitters and Drainlayers Act 2006. Connecting or disconnecting the water supply, waste trap, or drain must be done by a licensed plumber registered with the Plumbers Gasfitters & Drainlayers Board. Doing this work yourself is illegal and could void your home insurance.
If your bathroom has no existing vanity and you need new supply lines or waste runs roughed in, that's definitely a job for a licensed plumber. Similarly, if you're unsure about wall structure, fixing into concrete, or your bathroom is in a rental property subject to Healthy Homes Standards, get professional advice.
For the carpentry side — building and installing the cabinet box — a skilled DIYer can manage this. But if you'd prefer a guaranteed result, find a qualified local carpenter on tradedirectory.co.nz.
