Efflorescence on brick walls can be an unsightly problem, causing white, powdery deposits to form on the surface of the bricks. While it may look concerning, the good news is that efflorescence is generally not a major issue and is relatively easy to address.
In this guide, we explore efflorescence, why it occurs, and, most importantly, how to remove efflorescence and prevent it from returning.
Although efflorescence may seem daunting at first glance, it's a common occurrence that many homeowners and house builders encounter. With some knowledge and the proper techniques, you can quickly restore your brickwork to its original, pristine condition. Rest assured, by the end of this guide, you'll have the tools and understanding necessary to bid farewell to those unsightly stains for good.
What is efflorescence?
Efflorescence is a naturally occurring phenomenon that sometimes appears on the surface of cement-based building materials and clay products. As the cement and weather chemically react together, calcium hydroxide is produced. This reacts with carbon dioxide in the atmosphere to produce calcium carbonate, which manifests as a white solid.
What does efflorescence look like?
Efflorescence in the pores of the concrete can lead to the appearance of white patches on the surface or an overall lightening of the product, which can be mistaken for fading. Although the appearance can be worrying, the effects of efflorescence are purely aesthetic and do not alter the strength or durability of concrete.
What causes efflorescence?
Efflorescence occurs when brickwork is exposed to varying levels of moisture, which makes it important brickwork is kept dry. The following weather conditions increase moisture in the air and, as a result, increase the chances of efflorescence:
- Low temperatures
- Moist conditions, i.e. dew and condensation
- Rainfall
As well as the weather, these eight things can all make efflorescence more prevalent:
1. Moisture migration
The primary cause of efflorescence is the presence of moisture migrating through bricks and concrete. Water dissolves soluble salts inside bricks, concrete, or mortar, transporting them to the surface.
2. New projects
Efflorescence is very common in new brick and masonry construction. This is because the materials used contain soluble salts that are mobilised by moisture curing and water used during the construction process.
3. Improper drainage
Inadequate drainage around foundations, poor grading of soil, or clogged gutters and downspouts let excess moisture saturate masonry walls, facilitating efflorescence.
4. Indoor condensation
Condensation caused by humidity imbalances can wet interior masonry surfaces and draw salts out from the inside, leaving efflorescence deposits.
5. Deteriorating materials
As masonry ages and deteriorates, more soluble salts may be exposed and dissolved by infiltrating moisture, increasing efflorescence.
6. Deicing salts
In cold climates, the use of deicing salts on walkways and roads can lead to efflorescence if the salts are absorbed into the masonry.
7. Sea salt
Buildings in coastal areas may experience efflorescence due to airborne sea salt being deposited on the masonry surfaces.
8. Exposure to damp soil
If masonry comes into contact with damp soil, water-soluble salts can be absorbed into bricks, which causes efflorescence.
How to prevent efflorescence
Efflorescence can generally be expected to disappear over time, depending on the environment where the paving or brickwork is on a project. However, rainwater, being slightly acidic, can dissolve the surface deposit. Where paving/ brickwork is fully exposed to the weather, any efflorescence would normally be expected to disappear within the first year or two, although it might be longer for a sheltered site.
Preventing efflorescence can be tricky, especially managing the salt deposits the bricks and concrete surfaces are exposed to.
However, some things can be done to mitigate the risk of the powdery substance appearing on walls and block paving.
Before buying building materials
Before you purchase construction materials, you should check with the merchant that they store their bricks off the ground on shrink-wrapped pallets. This protects the building materials from rain and water, which can seep into the bricks and then be evaporated, leaving crystalline salt deposits on the outside of the bricks.
While building
Once the pallet has been opened, the bricks should be covered with a waterproof sheet to reduce the chances of water getting into the bricks.
Another thing you can do is cover the building surface with tarpaulin after completion to avoid cavities and moisture absorption. You could also use low-alkali cement, which will help reduce efflorescence.
After completion
Once you've finished building the wall, you can further protect it from brick efflorescence by applying the appropriate damp-proof courses.
Hydrophobic sealant, for example, can help to prevent water absorption and stop water travelling within building materials.
How to treat efflorescence
As we mentioned, efflorescence can be a problem that solves itself overtime with natural weather occurrences. But if you’re keen to tackle it there are things you can do.
Proprietary cleaners can be used for more immediate removal of efflorescence. Most proprietary cleaning treatments contain acids and detergents, so it is important to ensure that the manufacturer’s instructions and all relevant environmental regulations are followed. Incorrect or careless cleaning may result in injury or damage and discolouration to the surface of the concrete product.
It is advisable to carry out a test on a small and inconspicuous area of paving/ brickwork before undertaking cleaning over the complete area.
The procedure is best carried out in cool conditions as when the concrete is hot, rapid evaporation may lead to recurrence of deposits. It’s important that you take care when applying acid-based cleaners to concrete. As the acid attacks the concrete, over application may alter the appearance of the paving.
Once you’ve done, wash off the residue and inspect the area. In the case of stubborn or heavy deposits repeat the application as necessary.
After final application of the cleaner, wash off any residue with plenty of water to prevent staining, taking care to dispose of the run-off safely. Allow the area to dry and then inspect the surface.
The following minimum equipment is required:
- Protective gloves and goggles
- Appropriate footwear
- Brush with soft bristles
- Plastic watering can for application
- Supply of clean water
What happens if efflorescence is left untreated?
If efflorescence is found on exterior walls, it is not too threatening and could likely clear up when the weather changes.
However, if you notice efflorescence internally, it's a sign that your walls are damp, which can cause serious problems if left untreated. If you have efflorescence inside your home, it's a good idea to have your property looked at by a damp surveyor to get a good idea of how bad the problem is.
If you don't treat internal efflorescence, dampness can have a serious impact on your home and your health, including causing structural damage and giving you respiratory illnesses.
Maintain your property with Marshalls
If you're considering a new building project, whether for a garden wall or a new driveway, make sure you look at Marshalls' leading range of walling blocks, bricks and stones.
Alternatively, explore our blog for more advice on maintaining your home. Here, you'll find guides on how to clean block paving, how to clean patio slabs, and how to improve the kerb appeal of your home.
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