Why Does Water Get Inside Cavity Walls?

Understanding the common causes of moisture problems in brick veneer homes.
Common Symptoms of Cavity Wall Failure
1
Water Inside the Home After Rain
Damp patches, wet carpet edges or moisture marks after heavy rain are early signs of cavity drainage failure.
2
Blistering or Peeling Paint
Paint lifting from the wall surface usually indicates moisture trapped behind plasterboard.
3
Swollen Timber or Mould Growth
Moisture escaping from the cavity can affect skirting boards, window frames, and internal trims.
4
Leaks That Only Occur in Storms
If leaking is storm-dependent, the flashing or weep holes are no longer functioning as intended.
Result: If you see any of these signs, your cavity wall system may have failed and needs inspection before internal damage worsens.

Frequently Asked Questions

How a Cavity Wall Works
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A brick veneer wall has a gap (cavity) behind the bricks. This gap collects any rainwater that seeps through the bricks and then drains it out through:

  • Flashing (a waterproof layer)
  • Weep holes (small drainage openings)

When these parts fail or weren’t installed properly, moisture starts entering your home.

The Main Causes (Simple & Easy)
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Missing or Incorrect Flashing:

  • The flashing is what catches water inside the cavity and directs it out through the weep holes.
  • If no flashing was installed, water has nowhere to go and ends up leaking inside the wall.
Blocked Weep Holes
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Weep holes allow water to escape.When they become blocked by mortar, dirt, spider nests, paving or render, water becomes trapped and forces its way indoors. What customers usually notice:

  • Damp smell near skirting boards
  • Bulging paint
  • Efflorescence on bricks
Soil or Garden Beds Too High
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If soil, mulch, pavers or decking are built above the weep-hole height, water cannot escape naturally. Why this matters:

  • Water floods back into the cavity
  • Weep holes become completely useless
  • Continuous rising damp issues
Case - study

Cavity Wall Leaking – Strata Common Wall 2025

When we opened the wall, we found a significant amount of moisture trapped inside the cavity, which had been releasing into the internal floor area.

Cost from $725
linear metre for brick-removal sections
6years warranty
Final pricing may vary depending on wall layout, access, and the type of brick construction.
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Wall junction failure • Flashing limits • Moisture tracking

  • Water can enter through upper wall joints, windows, and box gutters
  • Musty smells or flooding often appear after heavy rain
  • Even well-designed cavity systems fail if construction execution is compromised

High-level water entry • Gutter defects • Repeated ingress

  • Even small defects in box gutters can push water into cavity walls, leading to mould, odours, and internal damage. Proper investigation prevents costly repeat repairs.

Slab edge breach • Cavity failure • Remedial membrane

  • Water entering through the slab-to-brick interface is a common issue not solved by patching. This project shows the need for roll-type membranes to redirect moisture safely outward.
Site research plan

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Cost-Effective Solution
Recommended approach balancing quality and budget.

Water penetration or Structural issue

$250+GST 

RISK-FREE RESEARCH: Your site inspection fee is fully CREDITED BACK to you when the project contract is signed. 

Category A:
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In-depth site-investigation;

comparative quote for the defined scope.

Detailed Scope of Work

Alternative Solution: Suggestion for a viable alternative if applicable (e.g., phased repair vs. full replacement).

On-Site Session:
- Time Management Planning & Risk Mitigation
- Scheduling & Project Protection Review

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Detailed Defect Report:

$750+GST

Analysis of issues and clear, expert solutions.

Category B
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Complex Assessment: Inspection of multiple units, common property, and complex strata defects.

Vertical Access Included:
Roofs and Balconies
requiring ladder access (up to 7M/two stories).

Concealed Spaces: Comprehensive review of Basements, Sub-floors, and confined areas.

Separate Quote: Provides an independent, comparative quote for the defined scope.

Clarity on Inspection & Report
FAQ
Service area: "Northern Sydney, the Inner West, and Greater Parramatta." more
1. What does Structural Access cover?
2. How do you perform leak and water testing?
3. When is a Structural Engineer required?
4. How quickly will I get my report?
5. Can I use this report for insurance claims?
6. Does the cost cover complex testing like jackhammering?
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