Key takeaways
- Efflorescence is soluble salt carried to the face of the brick by moisture and left behind as the water evaporates, so it is a moisture and materials problem before it is a cosmetic one.
- The salts come from several places on a building site, including the mortar, the sand, the bricks, the ground and any water that reaches the wall during construction.
- Keeping bricks dry, covered and off the ground prevents much of the efflorescence that appears on new face brick, because it removes the water that carries the salts.
- Cleaning mortar droppings promptly, and cleaning the face in the right order with dry brushing first and wet cleaning only after testing, avoids both staining and damage to the brick.
- Who is responsible for cleaning the brickwork, and how the cleaning is done, should be written into the contract before the wall is built rather than argued about after handover.
A few weeks after handover, a client rings to say the new brick has gone white. It looks like a fault, and the client is right to ask about it, even if the cause turns out to be simple. Efflorescence on face brick is one of the most common complaints in new masonry, and one of the least understood. Builders often treat it as a cleaning job to be done at the end. In practice, most of what causes it is decided long before the cleaning starts, in the way the materials are stored, the way the wall is covered and the way the mortar is handled as the work goes up.
This article is about the salts and the water: where the salts come from, how moisture carries them to the face, and what a builder can do during construction to stop it. It does not cover joint profiles or flashing detail, which affect where water gets into a wall and are dealt with in the article on masonry flashing and weephole detailing. The focus here is the materials on the ground, the wall while it is going up, and the clean-up that follows.
What efflorescence actually is
Efflorescence is a deposit of soluble salts left on the surface of masonry. Water carries dissolved salts through the brick and mortar. When the water reaches the face and evaporates, the salts are left behind as a white crystalline bloom, sometimes powdery and sometimes a hard crust. The water does not need to come through the wall to cause it. Moisture moving outward through a wall that is drying out can bring salts to the surface too, even where no leak exists.
There is a useful distinction between the efflorescence that appears during construction, which comes from salts in the materials and water used on the job, and the efflorescence that appears later, which usually comes from water getting into the wall in service. This article is about the first kind, because it is the kind a builder controls. The salts that show up in the first months often reflect how the wall was built rather than how it has been used, which is why the cause should be traced to the site rather than blamed on the weather.
The bloom can often be brushed off, and in many cases it fades as the wall dries. That does not make it a non-issue. A client who sees white marks on a new house does not see a process that will fade. They see a result, and the builder has to explain it and fix what is within their control.
Where the salts come from on a building site
Salts reach the face of a wall from several places, and most sites have more than one source at once. Cement and lime in the mortar contain soluble compounds, and the mortar is one of the main carriers of salt into the wall. The sand and aggregate in the mix can carry salts too, particularly if they have been stored where seawater, ground water or a contaminated surface has wetted them. Mortars mixed in proportions that differ from the specified mix change how much soluble material is present, and that is a quality control matter as much as a materials one.
The bricks themselves can carry soluble salts, and some clay bricks carry more than others. The brick manufacturer’s data is the place to check what a particular product is likely to do, and it is worth asking for that information before the order is placed rather than after the wall is up. Bricks stored on the ground or in wet conditions can also pick up salts from the soil and from splashback, and then carry those salts into the wall as the work goes up.
Groundwater and damp ground at the base of a wall are another source, and they are the one most often overlooked. Ground moisture can move up into the lower courses if the base is not detailed correctly, and the salts it carries are deposited where the water evaporates. This is where the design’s base detail matters, and it is worth checking that the detail was built as drawn before the lower courses are covered over.
How moisture carries the salts to the face
Salts do not move on their own. They need water, and the path the water takes decides where the salts end up. During construction the most common route is rain falling on the wall while it is being built. Freshly laid mortar and new brick absorb water readily, and a wall left open to rain will hold moisture for a long time. A wall that stays wet for days gives the salts in it time to move outward as it dries.
The second route is through the material stacks. Bricks stacked on the ground and covered with a cover that lets water run under it will draw moisture from the soil and hold it, and the packs above the wet ones will pick up that moisture as they are handled. The third route is inside the cavity, where mortar droppings and debris can hold water against the back of the leaf and keep it there. The fourth is the wall top, which is left open at the end of a day and collects water that then runs down into the work.
Each of these routes is a point where the builder can intervene. The salts are not the only variable. The time the water stays in the wall, and the drying that follows, determine how much salt reaches the surface. A builder who controls the water controls most of the outcome. The article on moisture in new construction materials and drying covers the drying side in more detail.
Sequencing the work to keep the salts out of the face
- 1Keep the bricks dryStack bricks off the ground, covered, and clear of splashback and run-off.
- 2Cover the wallCover the top of the wall at the end of each day and whenever rain is forecast.
- 3Control the waterWet bricks to the level the work needs and no further, so water does not carry salts into the face.
- 4Clear the droppingsRemove mortar droppings from the face and the cavity before they harden.
- 5Clean in the right orderDry brush first, and test any wet cleaning on a sample panel once the wall has dried.
- 6Agree the cleaning in the contractMake clear who is responsible for cleaning the brickwork, and how the cleaning will be done.
Keeping the bricks dry from delivery to the wall
The bricks should be stored off the ground on a firm, level base, and the stack should be covered with a cover that sheds water and does not trap it. A cover that sits on the stack without clearing the sides and the top is only partly useful, because water can run down into the stack and wick up from below. Keep the stacks clear of splashback from the slab or the path, and keep them away from the run-off from a roof or an excavation.
Stack the bricks so the packs do not sit in standing water after rain. Check the stacks after a storm, and move any packs that have been wet to a place where they can dry before they are used. A pack that is still wet on the day it is laid is a pack that will move salts toward the face. This is a small effort, and it is among the most effective things a builder can do early in the job.
Covering the wall, controlling the wetting and clearing the droppings
At the end of every working day the top of the wall should be covered, with a cover that is secured against wind and overhangs the wall on both faces. Cover the wall whenever rain is forecast, and do not start laying into a wet day in the expectation that the work will dry quickly. A wall covered at the end of each day is far less likely to hold moisture through the night, and fresh mortar that is protected has a better chance of curing without washing out.
Wetting the bricks before laying is standard practice, because it controls how quickly the brick draws water from the mortar. The amount has to be controlled. Over-wetting carries water, and whatever salts it holds, into the face and the cavity. The brick manufacturer’s and the mortar supplier’s guidance is the right reference for how much wetting a product needs, and a brick that is already saturated should not be laid at all. Wet the bricks in the amount the work needs, and no more.
Mortar droppings are the detail most often left to chance. Droppings that fall onto the face and harden become a source of salts and a stain that is hard to remove later. Droppings in the cavity hold moisture against the back of the leaf. Remove them as the work goes up, while they are still soft, with a clean scraper and brush, and keep the cavity clear as the wall rises. A few minutes at the end of each section saves hours of cleaning at the end of the job.
Where the salts come from, and the control on the job
| Source of the salts | Control on the job |
|---|---|
| Cement and lime in the mortar | Mortar mixed to the specified proportions, with the water used controlled |
| Sand and aggregate stored badly | Stored clear of the ground and covered, and kept free of seawater and run-off |
| Bricks with soluble salts | Manufacturer’s data checked before ordering, and stacks kept dry |
| Ground moisture at the base | Base detail built as drawn, and the lower courses checked before they are covered over |
| Mortar droppings on the face and in the cavity | Removed as the wall goes up, while they are still soft |
| Water left in the wall overnight | Wall top covered at the end of every day and whenever rain is forecast |
Cleaning in the right order, and only after testing
When efflorescence has appeared, or when the wall has been stained by droppings, the order of the cleaning matters. Dry brushing should come first, to remove loose salt and mortar without adding water. Wet cleaning should only follow once the wall has had time to dry, because water applied to a wet wall drives the salts further in and can produce a larger bloom the next time the wall dries out.
Cleaning the whole wall before testing a sample. The most expensive mistake is applying a strong wet clean to the whole wall before a sample area has been tested and before the wall has dried. It can drive the salts further in and leave staining that is harder to remove than the bloom it was meant to fix.
Test any cleaner on a sample area first. Strong acid cleaners can react with the mortar, leave marks and damage the face of the brick, and some products are not suitable for particular brick types at all. The product should be one the brick and mortar manufacturers recommend, applied at the strength they recommend, and rinsed thoroughly. A cleaner left on the face or rinsed poorly will leave salts of its own behind. Work in sections, and keep the cleaner off the joints and the frames.
Timing also affects the result. Cleaning a wall that is too young can damage the mortar and the joints, and cleaning a wall that is still damp can produce a bloom that appears later. Agree the timing with the supervisor and the client, and record the date, the product, the sample area and the result. That record is the evidence that the work was done properly, and it is what a builder will need if the question comes back.
A worked example: the coastal house and the wet stacks
Consider a builder on the coast who was building a brick veneer home in winter. The bricks had been stacked on the ground under a cover that sagged in the middle, so water collected on top of the stack and soaked the lower packs. The crew laid the wall through several wet weeks. At the end of each day the top of the wall was left uncovered, because the cover had been blown off once and not replaced. Mortar droppings were scraped from the face at the end of each section, but not from the cavity.
The white bloom appeared within a few weeks of handover, mostly on the lower courses and in the areas where the wall had been wettest during building. The client rang, and the builder went to see the house. The first step was to dry brush the face, which removed much of the loose salt and showed the extent of the problem. The builder then tested a wet clean on a sample panel after the wall had dried, using a product the brick manufacturer recommended at the strength it recommended. The panel came up well, and the rest of the wall was cleaned in sections under the same method.
The builder then changed the process for the next job. The bricks were stacked on a raised base under a proper cover, the cover was checked after each storm, the wall was covered at the end of every day, and the cavity was cleared as the wall went up. The site supervisor signed off the stacks and the cover each morning. The change cost little. It replaced a set of habits that had been left to chance with a set of checks that anyone on the crew could run.
Writing the cleaning responsibility into the contract
A great deal of the argument about efflorescence happens after handover, when the question of who pays for the cleaning is raised for the first time. The contract is the place to settle it. Where the builder’s materials, handling or sequencing contributed to the problem, the builder should expect to be asked to put it right. Where the cause lies elsewhere, the position is different, and the contract should say so. The NSW Government guidance on contracts for home building work is the place to check the basic requirements for a residential contract before the wall is built.
Write the cleaning method into the scope as well. A sentence stating that the brickwork will be dry brushed, and that any wet cleaning will be tested on a sample panel before use, sets expectations for both the builder and the client. It also gives the builder a defensible position if the cleaning is done properly and the client wants more. A builder who explains the process in writing before the wall goes up is rarely caught out when the question comes at handover.
The value of prevention is that it removes the argument rather than winning it. Efflorescence that never appears does not need to be explained, and the cost of prevention is small beside the cost of cleaning a finished wall, the callbacks and the damage to the builder’s reputation. The work for a site supervisor is to keep the bricks dry, the wall covered and the cavity clear. The PointCPD guide to how NSW builder CPD works explains how technical learning of this kind fits into the licence requirement.
Questions builders ask
What causes white marks on new face brick?
The marks are soluble salts that moved to the surface of the brick in water and were left behind when the water evaporated. The salts can come from the mortar, the sand, the bricks, the ground or water that reached the wall during building. Most efflorescence on new work is a combination of salts and moisture that the builder can influence.
Is efflorescence a defect?
It is usually a cosmetic problem, but a client will still see it as a defect, and it can point to moisture that needs attention. The response depends on the cause, the extent of the marks and the contract. Inspect it, establish the source and agree the treatment in writing before any work starts.
Can efflorescence be removed?
Often, but not always, and the method matters. Dry brushing removes loose salt first. Wet cleaning should only follow once the wall has dried, and it should be tested on a sample area, because the wrong product or too much water can damage the brick or leave new staining.
Should I wet the bricks before laying them?
Brick is usually wetted to control how fast it draws water from the mortar, but the amount has to be controlled. Over-wetting carries water and any salts into the face, which is a common route to efflorescence. Follow the brick manufacturer’s and the mortar supplier’s guidance, and do not lay bricks that are already saturated.
Does the cleaning method affect the brick?
Yes. Strong acid cleaners can react with the mortar and leave marks or damage the brick face, so they should not be used without testing. Gentle methods, applied after the wall has dried and tested on a panel first, are the safer choice on most jobs.
Who pays for cleaning efflorescence?
That depends on the contract and the cause. Where the builder’s materials, handling or sequencing caused the problem, the builder should expect to be asked to put it right. Where the cause lies elsewhere, the position is different. Put the responsibility in writing before the work starts, and check the defect provisions with an adviser.
Sources
- Continuing professional development for builders and swimming pool builders · NSW Government
- General building work licensing · NSW Government
- Home Building Act 1989 (NSW) · NSW Legislation
Published 28 September 2026. General information for builders, not legal, financial or engineering advice for a specific job. Check current requirements with the relevant regulator or standard before relying on them.
