The concern was that bricks had been submerged in floodwater, were muddy, and were then incorporated into the build.
The question was two fold:
1. Will the mud between the mortar leach out over the years? They are pale white-ish bricks.
2. Will sitting in flood waters change mineral composition of the brick, leading to ongoing efflorescence, vanadium staining etc
The following post is the reply I provided, based on my current knowledge and best understanding of the issue.
If you have more experience with this—or a better technical explanation—please reach out. I’d be happy to pass along more accurate information to the reader.
Hi Mary,
I'm assuming you're in Australia. My knowledge and experience are limited to Australian standards and residential construction practice.
To start, it's not good practice to lay dirty bricks. Bricks should be clean and dry when laid, unless they're a type the manufacturer says needs wetting (with clean water) to improve bond strength. Keeping them clean during laying also avoids aggressive cleaning later. Prevention is always better than cure.
That said, a lot depends on how much of the facade is affected. I'm picturing a wall of completely muddy bricks, but that's a mental image, not an inspection, so I can only speak in general terms.
I've gone back through the Australian Standards and industry guides, and honestly, this is one of the most frustrating parts of construction. I wish more builders and trades just tried harder to prevent situations like this in the first place.
C11 - Enclosed Stage Inspection Checklist
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Last updated 28 Oct 2026 · Revision 6 · Free updates for life
Checklist Type: Major (Enclosed Stage)
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When to use: Enclosed (lock-up) stage: brickwork and external cladding
A 152-point enclosed stage checklist for brick veneer and fibre cement, weatherboard or foam cladding. Check the cavity, ties, flashings, windows and lintels before the linings hide them.
Reader Question
Will the mud between the mortar leach out over the years? They are pale white-ish bricks.
Will sitting in flood waters change mineral composition of the brick, leading to ongoing efflorescence, vanadium staining etc
1. Will the mud leach out of the mortar over time? Could flood exposure change the brick and cause efflorescence or vanadium staining?
- Unless there's a constant source of water behind or above the wall keeping it wet, there shouldn't be ongoing leaching of mud through the wall. Leaching, vanadium and calcium staining, and efflorescence (white salt deposits) usually happen when masonry stays damp over time. Normally brickwork gets wet and dries out repeatedly, and the cavity, weep holes and eaves help it dry, especially in a standard brick veneer house with eaves. I can't give a definitive answer without seeing the site, though.
- If the mud was high in red oxide, it could affect the mortar colour or cause staining over time. That also depends on how the joints were finished (flush, weather-struck, shallow or deep ironed) and on things like shade, trees, humidity and orientation that keep the wall damp.
- Water being drawn from the back of the wall to the face (capillary action) also depends on voids or large lumps in the mortar. Unless the mortar was poorly mixed, I doubt that applies here.
2. Could muddy bricks have changed the mortar mix or its performance?
Yes, you could argue that. If enough bricks were laid with heavy mud on them, the mud could act like a pigment or contaminant in the mortar, so it no longer matches the specified mix.
Mortar should be made with clean sand, low in salts and organic matter. Adding mud, even by accident, undermines that.
3. Did the floodwater affect the bricks before laying?
That depends on how long they were in the water. Saturated bricks should be left to dry before laying. If they weren't, the bond between mortar and brick may be weaker, because a wet brick's initial rate of absorption (IRA, how quickly it soaks up water from the mortar) is reduced. A good bricklayer may have adjusted the mortar mix to suit, but whether that happened here is unknown.
Images and Documentation
If you haven't already, take clear photos of how the bricks were stored, how they were laid, the muddy areas, and progress shots of the brickwork going up. Site diary notes on when you were on site and conversations with the builder or trades will also help later.
Insurance Work?
Was this part of an insurance claim? If so, there's usually a project manager or supervisor who has to sign off the works, and often the homeowner too. If it's an insurance job, I'd recommend not signing anything until you have written confirmation from the builder about the quality and compliance of the brickwork.
Contacting the Brick Supplier
It's worth talking directly to the brick supplier or their local rep. Explain what happened and ask whether the conditions and workmanship meet their laying recommendations, which usually follow the Australian Standards but may add guidance for that brick type or finish.
Surface Finish and Acid Washing
Acid washing will probably improve the look of the brick and mortar, but it has to be done right, using the method and dilution in the brick manufacturer's guidelines and the cleaning guidance in AS 4773.2.
And to your point: although the NCC doesn't explicitly say bricks must be clean, industry tolerance guides treat visibly dirty or stained brickwork as a defect. So dirty brickwork isn't something to accept as "just cosmetic".
Relevant Standards
The main Australian Standards covering masonry and bricklaying are:
- AS 3700 – Masonry Structures, and
- AS 4773.2 – Masonry in Small Buildings – Construction.
For houses, AS 4773.2 is the more directly relevant one, as it covers typical brickwork in houses and small buildings.
AS 4773.2:2015: Cleaning Masonry (Appendix B)
AS 4773.2:2015 has an informative appendix on cleaning masonry, including acid washing (Appendix B, "Cleaning Masonry"). Informative means it's guidance, not mandatory, unless your contract or the builder's QA process calls it up.
It's still a useful reference on which cleaning methods suit which bricks (alongside the brick supplier's recommendations).
Standards Australia's access options for homeowners change from time to time, so check their website for current options before you buy a standard for a one-off read.
Ultimately, the contractor is responsible for choosing the right cleaning method, including dilution, timing and process, so the brick and mortar aren't damaged.
What Does the NCC Say About Brickwork Finish?
The NCC refers to AS 3700 or AS 4773 for masonry. Those requirements focus on performance, such as:
- Cavity widths
- Weep hole spacing
- Damp-proof course (DPC) placement
- Wall tie spacing
- Structural durability
But the NCC does not explicitly say bricks must be clean before laying. AS 3700 is about strength, durability, joints and weatherproofing, not appearance.
Industry Best Practice and Inspection Expectations
Even though the standards don't spell it out, industry best practice clearly expects brick faces to be clean before and after laying. Builder QA manuals, inspection checklists and supervisor training all treat it as a basic sign of competent bricklaying.
Standards and tolerances guides
In Queensland, the QBCC Standards and Tolerances Guide is the main reference for what counts as a defect, so check the current edition. For comparison, the NSW Guide to Standards and Tolerances (2017) has specific statements on masonry:
- “Unless documented otherwise, masonry is defective if it is not laid true or with finish face outwards.”
- “Unless documented otherwise, masonry faces are defective if they are not cleaned and free of excess mortar.”
- “Stains, mortar smears and damage caused by cleaning are defective if they are visible from a normal viewing position.”
That matches the common understanding in the industry: the finished facade should be clean and presentable, not smeared, stained or visibly dirty, even if it doesn't affect structural performance.
Think Brick Manual 10: Construction Guidelines for Clay Masonry
Mortar Bond Strength & Dirty Bricks
Manual 10: Construction Guidelines for Clay Masonry (published by Think Brick Australia) discusses how the brick surface affects mortar bond.
In short: bricks shouldn't be wetted before laying except as a last resort, and it's better to adjust the mortar than to soak the bricks. Some water moving from the mortar into the brick helps the bond, but too much or too little weakens it, and laying wet bricks that contain manganese can cause manganese staining. Muddy or wet bricks interfere with this initial rate of absorption, which is why clean, dry bricks are recommended unless the manufacturer says otherwise. Manual 10 is available from Think Brick Australia.
Manual 10 also notes there's no routine site testing of mortar. Testing is only for exceptional cases where problems are evident, and even then it's best to test the built masonry.
Mortar Technical Guides
Mortar technical guides say sand for mortar should be free of impurities like organic matter (leaf litter, loam and soil), salts, clay lumps and fine silts. Salts can lead to salt attack, and clays and silts weaken the mortar. Mud from floodwater brings all of these with it.
If You Wanted to Push the Issue Further (Use with Caution)
Mary, if you really wanted to press the issue, there are a few arguments you could raise, though I'd use them with care.
1. Surface Coating and Mortar Bond Strength
You could argue the mud acted as a coating on the brick, which should have been discussed with the brick manufacturer, because surface conditions affect how well mortar bonds.
Dirty bricks may absorb less water from the mortar, which is key to a proper bond. If the bricks couldn't absorb moisture as designed, the bond strength may be compromised.
2. Requesting a Mortar Scratch Test or Chemical Analysis
To check the wall more formally, you could request a scratch test (or even a chemical analysis) to verify the mortar's durability and composition, and confirm it meets your site's exposure classification (e.g. near the coast or industry).
Tests can be arranged through the builder or brick manufacturer, though suppliers often won't deal directly with homeowners because you're not their client.
3. Exposure Classification (Rarely Considered)
Very few builders document the site's exposure classification in their contracts, but it matters: it sets the required mortar class (M3, M4 and so on) and the type of wall ties and accessories.
If it wasn't considered and the mortar doesn't meet the required durability, that's a more serious concern.
4. Improper Storage of Materials
If relevant, you could also raise poor storage of bricks on site. Most manufacturers say pallets and part-built walls should be protected from rain to avoid excess water and efflorescence.
Would Any of This Matter Without Litigation?
These points are valid, but they usually only gain traction in formal complaints or legal disputes, and that road is rarely fun. Once the wall's built, the question becomes: what can I still do?
5. Practical Steps You Can Take Now
- Ask the builder for a written guarantee that any visible staining or discolouration of the brick or mortar caused by the muddy bricks will be fixed at no cost to you.
- If they refuse, follow up in writing and ask for the brick manufacturer to do a mortar scratch test (they usually have the equipment; the builder won't). If the mortar doesn't meet spec, you have leverage: the wall comes down, or you negotiate a compromise.
- One compromise could be a penetrating water-repellent sealer (silane/siloxane type) on the brickwork, applied as directed by the brick supplier. These repel water and help limit efflorescence and staining. As long as the tops of the walls are protected and no moisture gets in behind, this could be a fair middle ground.
- If discolouration shows up after handover, photograph it and report it to the builder in writing. Queensland's standard contracts give a 12-month defects period from practical completion, so include it in your defects list (our C18 6 Month Maintenance checklist helps). For QBCC home warranty insurance, non-structural defects must appear within 6 months of completion and be lodged within 7 months, so don't wait.
Final Thoughts
This is one of those frustrating grey areas, Mary, because nowhere in the standards does it explicitly say "bricks must be clean before laying". It seems like common sense, but it isn't spelled out. I hope the above gives you some practical options and talking points with the builder, the insurer or anyone else.
Thanks Mary
🤔 Dear readers,
If you have more experience with flood-affected bricks, or a better technical explanation, I'd love to hear from you. I'm a builder who knows a fair bit about some things, but not everything.
Your insights might just illuminate them, so please don’t hesitate to get in touch.
Further Reading
Brick Veneer Facades: A Complete Guide for Aussie HomesBrick veneer facades are a popular, durable, and generally low maintenance option for your home façade. In this post we cover all the essential elements and best practices in brick veneer wall construction.
Exploring the 8 Types of Brick Masonry in House ConstructionBrick masonry is a popular choice for house construction due to its durability, aesthetics, and flexibility. But did you know there are eight different types of brick masonry that can be used? Each type has its own unique characteristics that make it suitable for different applications.
Efflorescence on Concrete & Brick: Prevention & TreatmentEfflorescence, the white powdery substance on concrete and brick surfaces, can be a homeowner’s nightmare. Caused by water seeping through and evaporating, it’s not just unsightly but can indicate deeper issues. Dive into understanding its causes, prevention, and effective treatments.
C11 Enclosed Stage Checklist for New Home BuildsIf you’re building a new home, knowing what to check at the “enclosed” stage is important. In this post we give you a super detailed “overview” (grab a coffee or three) of our C11 Enclosed Stage Checklist, helping you check for quality at the enlcosed stage of construction.
