Waterproofing is designed to protect your home from hidden water damage. When it fails, the damage often starts silently—behind tiles, under floors, and inside walls. By the time it becomes visible, repairs can be costly.
In this 2026 guide, Noble Tiling Solutions explains the most common signs of waterproofing failure, why they occur, and the correct steps to take next.
Persistent Mould or Mildew Smell
A constant damp or musty smell—especially in bathrooms or laundries—is often the first warning sign.
Why it happens:
- Moisture trapped behind tiles
- Failed membrane allowing water penetration
- Poor ventilation worsening the issue
Image:
Bathroom corner with mould growth near grout lines.
Discoloured or Darkened Grout Lines
When grout stays dark long after cleaning, it often means moisture is coming from beneath—not the surface.
What it indicates:
- Water trapped under tiles
- Failed waterproofing layer
- Grout absorbing moisture from below
Loose, Hollow, or Lifting Tiles
Tiles that sound hollow when tapped or begin to lift are a serious red flag.
Common causes:
- Adhesive breakdown due to moisture
- Waterproofing failure under the tile bed
- Movement caused by water damage
Image:
Close-up of lifted floor tiles near a shower drain.
Cracked Grout or Tile Movement
Repeated cracking—even after repairs—usually means the problem is deeper than the surface.
Possible reasons:
- Moisture-related expansion
- Weak screed under tiles
- Compromised waterproof membrane
Surface repairs alone will not solve this issue.
Water Stains on Adjacent Walls or Ceilings
Stains appearing in nearby rooms or ceilings below bathrooms are a critical warning sign.
This indicates:
- Long-term water leakage
- Structural exposure to moisture
- Immediate professional attention required
Peeling Paint or Bubbling Plaster
When moisture migrates beyond wet areas, finishes begin to fail.
Watch for:
- Peeling paint
- Bubbling plaster
- Swollen skirting boards
These signs often appear after waterproofing has already failed.
Balcony or Shower Drainage Problems
Pooling water or slow drainage accelerates waterproofing breakdown.
Common issues include:
- Incorrect screed slope
- Blocked drains
- Membrane failure at junctions
Image:
Balcony with visible water pooling after rain.
What Causes Waterproofing to Fail?
Most failures are caused by:
- Unlicensed installation
- Poor surface preparation
- Insufficient membrane thickness
- Incorrect curing time
- Building movement
- Age (older installations)
In Melbourne, non-compliant waterproofing is one of the leading renovation defects.
What Should You Do If Waterproofing Has Failed?
Correct steps to take:
- Stop surface repairs (re-grouting alone won’t fix it)
- Arrange a professional inspection
- Identify the failure area
- Remove affected tiles
- Re-waterproof to AS3740 standards
- Re-tile with correct preparation
Early action saves significant repair costs.
FAQs – Waterproofing Failure
1. Can waterproofing be repaired without removing tiles?
In most cases, no. Failed membranes usually require tile removal.
2. How long should waterproofing last?
Properly installed waterproofing should last 15–25 years.
3. Is waterproofing failure covered by insurance?
Only if installed by licensed professionals and compliant with standards.
4. Can balconies fail faster than bathrooms?
Yes. Weather exposure increases failure risk if not installed correctly.
If you suspect waterproofing failure, don’t wait until damage spreads.
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