Efflorescence is something that many homeowners notice after new paving, brickwork, or garden walls are installed, a light-coloured, powdery residue that seems to appear from nowhere. It can look alarming, especially on a newly finished surface, but the good news is that it’s a very common and usually harmless phenomenon.
This article explains what efflorescence is, why it happens, how long it tends to last, and what you can (or can’t) do about it.
What exactly Is Efflorescence?
Efflorescence is a chalky white deposit that can form on the surface of masonry, concrete, render, or stone. It’s caused by salts within the material being drawn to the surface by moisture. Once the moisture evaporates, the salts are left behind, creating the familiar white marks or dusty residue.
Efflorescence can appear on paving, steps, walls, or even mortar joints. While it may be unwelcome from an aesthetic point of view, it is generally not a structural concern.
Why Does It Happen?
Efflorescence occurs when three things are present:
- Water-soluble salts in the building materials (e.g. bricks, mortar, concrete).
- Moisture, which dissolves those salts and draws them toward the surface.
- Evaporation, which causes the moisture to leave the salts behind as a visible residue.
It’s especially common in newly constructed features, because moisture is still being released from within the materials as they cure and settle.
Retaining walls, raised beds, and structures that bear against soil or sit in damp conditions are particularly likely to show signs of efflorescence during their first few months.
How Long Does It Last?
In most cases, efflorescence will fade or disappear over time. As the materials dry out and the salt content naturally decreases, there’s less moisture movement and less chance of surface deposits forming.
Depending on weather conditions and location, it may last a few weeks or a number of months, but typically no more than a year. Areas with more consistent sun and air movement will usually clear more quickly.
Persistent or recurring efflorescence might point to ongoing moisture exposure, but in the majority of garden settings, especially after new work, it’s simply part of the bedding-in process.
Can It Be Removed?
Yes – in most cases, it’s relatively easy to remove or at least improve:
- Dry brushing: Use a stiff, non-metallic brush to sweep away the dry salts. Avoid wire brushes, which can damage the surface of bricks or paving.
- Gentle rinsing: A light rinse with clean water and brushing can help, but avoid over-wetting the surface, which can dissolve salts back into the material and prolong the process.
- Specialist cleaners: For stubborn cases, there are proprietary efflorescence removers available, typically mild acidic solutions designed for masonry. Always follow instructions carefully and test on an inconspicuous area first.
In many cases, however, the best approach is patience: Let the structure dry out and settle naturally, and the efflorescence will often resolve itself without any intervention.
Is It a Sign of Poor Workmanship?
Not at all. Efflorescence is a natural chemical process, not a defect. It occurs across all kinds of masonry work, whether installed by specialists, DIYers, or major contractors. The appearance of efflorescence doesn’t mean anything has been done wrong, and it doesn’t affect the strength or durability of the structure.
We often advise clients that this is a short-term cosmetic issue and part of the normal life cycle of new masonry. If you’re seeing it, try not to worry, and if you’re unsure, it’s always fine to ask for reassurance or advice.
© The London Front Garden Company 19 August 2025