- What Are Weep Holes and What Do They Do?
- Why Weep Holes Fail
- How to Tell If Your Weep Holes Are Blocked
- When This Becomes a Building Defect
- What a Forensic Waterproofing Inspection Covers
- What to Do Next
- Frequently Asked Questions
Weep holes are small, but the problems they prevent are anything but. If yours are blocked, there may already be water sitting inside your wall cavity right now — and you'd have no way of knowing.
This article explains what weep holes do, why they fail in brick veneer construction, and how to check whether yours are working. If you're already dealing with water damage or a dispute with your builder over defective waterproofing, the final section covers what to do next.
What Are Weep Holes and What Do They Do?
Weep holes are small openings left in the mortar joints of a brick veneer wall, typically positioned at the base of the wall just above the flashing. In a standard brick veneer home, the brick skin isn't structural — it sits roughly 50mm away from the timber or steel frame, leaving a cavity between the two.
That cavity is designed to drain. When rain drives against the wall, some water will always get past the brick face. The flashing at the base of the cavity catches it and directs it toward the weep holes, where it exits safely.
Without functioning weep holes, that water has nowhere to go. It pools on the flashing, rises, and eventually finds its way into the frame, the flooring, or the internal wall lining.
Weep holes also ventilate the cavity. Moving air reduces moisture build-up and slows the conditions that lead to timber rot, mould, and corrosion of wall ties.
Why Weep Holes Fail
Weep holes fail for a small number of predictable reasons. Most are installation problems, not maintenance problems.
Mortar Droppings During Construction
This is the most common cause. As bricklayers lay courses above the flashing, mortar falls into the cavity and lands below. If it isn't cleaned out before the next course goes up, it sets solid — creating a dam that blocks drainage entirely, regardless of whether the weep holes themselves are open.
The result is a wall that looks correct from the outside but can't drain internally. Water backs up behind the flashing and eventually saturates the base of the frame.
Weep Holes Filled or Painted Over
It happens more often than it should. Weep holes are sometimes filled with mortar by bricklayers who consider them untidy, or painted over during external repaints. Either way, the opening is sealed and the drainage path is gone.
Incorrect Spacing or Omission
Australian Standard AS 3700 sets out requirements for masonry construction, including weep hole placement. The general requirement is a weep hole at every second perpend (the vertical mortar joint) above the flashing, giving a maximum spacing of roughly 1200mm. Where weep holes are spaced too far apart, or omitted entirely over sections of wall, drainage is inadequate.
This is a construction defect, not wear and tear.
Insect Mesh Installed Incorrectly
Weep holes are sometimes fitted with mesh or proprietary inserts to keep insects and vermin out of the cavity. These are legitimate products when installed correctly. When the mesh is too fine, or packed in with mortar, it restricts flow and defeats the purpose.
Flashing Defects
Weep holes only work when the flashing behind them is intact and correctly lapped. If the flashing is torn, incorrectly lapped, or terminates short of the weep hole opening, water drains into the wall rather than out of it. The weep hole may be open, but the system still fails.
How to Tell If Your Weep Holes Are Blocked
You don't need specialist equipment to do a basic check. Walk around the base of your external brick walls and look at the mortar joints just above the damp-proof course — usually the first or second course above ground.
You should see small open gaps, roughly 10mm wide, at regular intervals. If you can't find them, or every joint appears fully mortared at that level, that's worth investigating.
Here are the specific signs to look for.
Visible signs from outside:
- No open joints visible at the base of the wall
- Mortar or paint filling the joints at that level
- Efflorescence (white salt staining) on the brick face, which indicates moisture moving through the wall
- Staining or tide marks on the brickwork below window sills or at wall bases
Signs from inside:
- Damp patches or staining at the base of internal walls
- Swelling or lifting of skirting boards
- Mould growth at floor level near external walls
- A musty smell in rooms adjacent to external brick walls
- Soft or springy flooring near external walls, which can indicate subfloor framing damage
Any of these signs warrants a closer look. The presence of several together — particularly internal dampness combined with no visible weep holes externally — is a strong indicator of a drainage failure.
When This Becomes a Building Defect
A blocked or missing weep hole isn't a cosmetic issue. It's a functional failure of the wall drainage system, and it can cause significant structural damage over time.
Under the Home Building Act 1989 (NSW), major defects in residential building work carry a six-year warranty period. Water damage resulting from defective waterproofing or drainage is commonly classified as a major defect. If your home is within that period and the builder is responsible for the construction, you may have a claim.
The challenge is proving it. A builder's response will almost always be that the damage has another cause, or that the weep holes were compliant at the time of construction. To counter that, you need an independent forensic inspection and a written report that documents the defect, its cause, and the resulting damage in a form that NCAT or a court will accept.
What a Forensic Waterproofing Inspection Covers
A forensic waterproofing inspection goes well beyond a visual check. It documents the condition of the weep holes, the flashing, the cavity, and any resulting damage to the structure. Where access allows, it may include moisture readings, probing of affected materials, and review of the original construction documentation.
The output is a written report that identifies the defect, attributes it to a cause, and quantifies the damage. When that report is prepared by an independent building consultant with no affiliation to the builder or insurer — and when it satisfies the UCPR Schedule 7 Expert Witness Code of Conduct — it carries genuine weight in NCAT proceedings and in court.
At Awesim Building Consultants, forensic waterproofing inspections are conducted on-site across NSW, including regional areas from Tweed Heads to Tamworth. Reports are prepared to be court-ready, not just descriptive. If your matter proceeds to NCAT or the District Court, the same report can be used as expert evidence.
What to Do Next
If you've identified signs of blocked weep holes or water ingress, don't wait for the damage to worsen before getting a professional assessment.
Start by documenting what you can see now. Take dated photographs of any staining, mould, or damaged materials, and note when you first noticed the problem. That contemporaneous record becomes useful evidence later.
Then get an independent inspection. The sooner a defect is documented, the easier it is to establish when it occurred and who is responsible.
If you're already in a dispute with your builder, or NCAT proceedings are pending, a forensic waterproofing report may be exactly what your solicitor needs to support your claim. You can start with a free initial consultation by calling 1800 293 746 or visiting awesim.com.au.
Frequently Asked Questions
What are weep holes in brick veneer walls?
Weep holes are small open gaps left in the mortar joints at the base of a brick veneer wall. They allow water that enters the cavity between the brick skin and the frame to drain out, and they ventilate the cavity to reduce moisture build-up.
How do I know if my weep holes are blocked?
Look at the mortar joints at the base of your external brick walls, just above ground level. You should see open gaps at regular intervals — roughly every 1200mm. If all joints appear fully mortared, or if you can see efflorescence, internal damp patches, or swelling skirting boards, your weep holes may be blocked or missing.
Are blocked weep holes a building defect in NSW?
Yes. Blocked or missing weep holes that cause water ingress or structural damage are generally considered a building defect under the Home Building Act 1989 (NSW). Major defects in residential construction carry a six-year statutory warranty period.
Can I fix blocked weep holes myself?
If the blockage is surface mortar or paint, carefully raking out the joint may restore drainage. However, if mortar droppings inside the cavity are blocking the flashing, or if the flashing itself is defective, surface-level repairs won't resolve the underlying problem. A professional inspection is needed to confirm the cause before any remediation work begins.
What is a forensic waterproofing inspection?
A forensic waterproofing inspection is a detailed on-site assessment that documents defects in a wall's drainage and waterproofing system, identifies the cause, and quantifies the resulting damage. When prepared by an independent consultant to satisfy UCPR Schedule 7, the report can be used as expert evidence in NCAT or court proceedings.
How long does water damage from blocked weep holes take to appear?
It depends on rainfall, wall orientation, and the extent of the blockage. In some cases, internal damage becomes visible within months of construction. In others, it develops gradually over years. The absence of visible damage doesn't mean the cavity is dry — which is why a forensic inspection uses moisture meters and probing rather than relying on visual checks alone.
Do I need a solicitor before getting a forensic waterproofing inspection?
No. Many homeowners commission an inspection first to understand whether they have a viable claim before engaging a solicitor. The report then helps the solicitor assess the strength of the case and advise on the appropriate forum — whether that's NCAT, the Local Court, or the District Court.
Weep holes are a small detail with large consequences when they fail. If you have any reason to suspect yours are blocked, the time to investigate is before the damage spreads — not after. An independent forensic inspection gives you a clear picture of what's happening inside your wall and, if needed, the documented evidence to support a claim.
