Yes, you can carry out a basic visual inspection of your bathroom waterproofing yourself — and it's a smart thing to do regularly. Waterproofing failures are one of the most common and costly defects found in NZ homes, and catching problems early can save you thousands in repairs. That said, a thorough assessment of hidden damage really does need a licensed building inspector.
Why Bathroom Waterproofing Matters in New Zealand
Under the NZ Building Code, clause E3 (Internal Moisture) requires that wet areas like bathrooms are waterproofed to prevent moisture damaging the building structure. Most NZ bathrooms use a membrane system — either a liquid-applied membrane or a sheet membrane — beneath tiles or other wall and floor linings. When this membrane fails, water can silently rot framing, corrode fixings, and grow mould for months or years before you notice visible damage.
Because NZ has a wide range of climates — from humid Northland to cold, damp Southland — moisture management is critical in every region. BRANZ research consistently identifies bathroom leaks as a leading cause of building defects in NZ homes.
What You Can Check Yourself
A careful homeowner can identify many warning signs with nothing more than good lighting, a torch, and a keen eye. Work through the following checks systematically.
1. Look for Visible Water Staining and Discolouration
- Check walls and floors around the shower, bath, and toilet base for yellowing, brown staining, or tide marks.
- Look at the ceiling of the room below (if there is one) for water stains or bubbling paint.
- Inspect skirting boards and wall linings adjacent to the wet area for swelling, warping, or soft spots.
2. Check Grout and Silicone Joints
Grout and silicone sealant are the first line of defence, but they are not the waterproofing membrane itself. However, failed joints allow water to reach the membrane.
- Look for cracked, crumbling, or missing grout, especially at floor-to-wall junctions.
- Check silicone beads in corners and around fittings — silicone that is peeling, mouldy, or pulling away from the surface needs replacing.
- Press gently on wall tiles near the shower: any movement or hollow sound (tap with your knuckle) can indicate the adhesive or substrate behind has been compromised by moisture.
3. Inspect Around Penetrations and Fittings
Water most commonly enters around pipe penetrations, shower niches, tapware, and drain flanges — anywhere the membrane has been cut or sealed.
- Check around the shower drain for lifting or cracked sealant.
- Look at where tapware and shower heads exit the wall for gaps or discolouration.
- Inspect the toilet base for any soft flooring or staining.
4. Check for Mould and Musty Odours
- Surface mould on grout is common and often cosmetic, but mould appearing on painted walls, ceilings, or in cupboards adjacent to the bathroom can signal moisture moving through the structure.
- A persistent musty smell even after ventilating the room is a red flag worth investigating further.
5. Simple Moisture Check
You can use an inexpensive moisture meter (available from Bunnings or Mitre 10) to test wall linings adjacent to the shower. Readings significantly above ambient levels in surrounding dry areas suggest moisture is present in the substrate.
What You Cannot Easily Check Yourself
Some failures are hidden and require professional tools or invasive investigation:
- Membrane integrity beneath tiles cannot be confirmed visually — a building inspector may use thermal imaging cameras or professional-grade moisture meters.
- Structural framing damage behind linings is invisible without opening walls.
- Subfloor damage beneath a tiled floor requires either inspection from below or removal of flooring.
- Compliance of the original installation with NZ Building Code clause E3 and relevant standards can only be assessed by someone with the right knowledge and experience.
A Simple Self-Check Summary
| What to Check | Tool Needed | DIY Friendly? |
|---|---|---|
| Grout and silicone condition | Eyes, torch | Yes |
| Tile movement / hollow sound | Knuckle tap | Yes |
| Staining on walls, ceilings, skirtings | Eyes, torch | Yes |
| Surface moisture levels | Moisture meter | Yes |
| Membrane integrity beneath tiles | Thermal camera | No — professional |
| Structural framing damage | Invasive inspection | No — professional |
When to Call a Professional
If your self-check turns up any of the following, it's time to bring in a licensed building inspector:
- Soft, spongy, or springy flooring near the shower or toilet
- Tiles that move, crack, or sound hollow across a wide area
- Visible mould or staining on walls outside the wet area
- A musty smell that won't go away
- Any moisture meter readings that concern you
- You're buying or selling a home with a tiled bathroom
A Licensed Building Practitioner (LBP) or qualified building inspector can carry out a thorough assessment and provide a written report. If waterproofing repairs or re-lining are needed, check whether a building consent is required — this depends on the scope of work and your local council's interpretation of Schedule 1 exemptions under the Building Act. Always confirm with your council before starting work. You can find qualified local building inspectors on tradedirectory.co.nz.
Note that any plumbing work involved in repairs — such as moving or replacing waste pipes or tapware — is restricted work that must be carried out by a licensed plumber registered with the Plumbers, Gasfitters and Drainlayers Board.
Licensed Building Practitioner (LBP)
BCITO Qualified
