Part of the guide: The Construction Defect Field Guide: 40 Defects by Trade, With Photos
Almost every new brick house grows a white bloom on its face in its first spring, and almost every buyer asks what it is. The honest answer is dull: the wall is drying out. The useful answer is that the pattern of the bloom tells you whether the drying out is all that is happening, and an inspection that just writes "efflorescence, cosmetic" has read the first word and stopped.
What does efflorescence look like?
A white, sometimes greyish, powdery or fluffy deposit on the face of brick, block, mortar or render, usually patchy rather than uniform, worst on the elevations that get the weather and after wet spells. Fresh efflorescence brushes off dry and dissolves if you wet a fingertip and touch it. It is not mould (mould is black, green or grey and grows in shaded, damp places), not paint splash, and not the harder, whiter crust of lime bloom, which is covered below because it is regularly confused with it.
The pattern is the diagnostic. A general light haze across an elevation is one thing; a heavy band under every cill, a streak beside a downpipe, or a line 150 mm above the ground is something else.
Why does it appear on new brickwork?
Bricks, sand and cement all contain small quantities of soluble salts, sulphates mostly, some chlorides, as a natural part of the material. Water moving through the wall dissolves them. When the water reaches the face and evaporates, the salts are left behind as crystals. Three ingredients, then: salts, water, and a surface to dry on. The salts are always present; what makes a new wall bloom is the water.
A new wall is wet from the start. The mortar was mixed with water, the bricks were often stacked uncovered in the rain, and the wall was built through weather without its copings, cills or gutters in place. All that water has to come out through the face, and it brings the salts with it. The first warm, dry spell after completion , usually the first spring, is when the bloom appears, and it can look alarming precisely because the wall is drying quickly.
That construction water is finite. Once it has gone, so has the transport for the salts, which is why efflorescence on a new building is expected to fade within a year and to be gone by the second. A wall that keeps blooming has a second water supply: rain getting in through a detail that does not shed it, ground water rising past the damp-proof course, or a leak.
Is efflorescence a defect?
General drying-out bloom is not. It does no harm to the brick, it brushes off, and warranty standards treat it as a normal temporary condition rather than something the builder has to remedy. Reporting it is still right: the client will ask, and a dated photograph of the extent is what shows next year whether it has faded as it should: but it goes on the list as low severity with a one-line action.
Three situations change that:
- Localised and persistent. A deposit that keeps returning in one place after brushing, especially in the second year, is a water-ingress symptom. The defect is whatever is letting the water in : an open coping joint, a cill without a drip, a leaking gutter or downpipe joint, ground built up over the DPC: and that is the item, at the severity the water path deserves.
- On the inside face. Salts on an internal wall surface, or fluffy deposits behind peeling paint, mean water is coming through the wall. That is never cosmetic.
- Spalling. When salts crystallise just below the surface instead of on it, the growing crystals can push the face of a soft brick off in flakes. Rare on modern facing brick, more common on reclaimed or low-fired brick, and a material or exposure question rather than a cleaning one.
The field guide entry puts general efflorescence at low and sends the recurring local version to the damp staining item two entries earlier, which is the right place for it.
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Efflorescence or lime bloom: how do you tell?
Lime bloom: calcium carbonate leaching out of fresh mortar or concrete and setting on the surface, looks similar at a distance and behaves completely differently. It is harder, whiter, often follows the mortar joints or runs down from them in streaks, and it does not brush off, because it has reacted with the air and turned back into a form of limestone. Water does not dissolve it. A drop of household vinegar fizzes on lime bloom and does nothing on efflorescence, which is the only field test you need.
It matters because the treatments are different: efflorescence is brushed off dry and left to stop on its own, while lime bloom needs a proprietary acid-based cleaner applied by someone who has used one on facing brick before. Writing "efflorescence" on a lime bloom item sends the contractor out with the wrong brush.
How do you report it?
- Location and extent: elevation, and whether it is general or concentrated. "Light general bloom, front and gable elevations" is a different item from "heavy band below all first-floor cills, front elevation".
- Photograph: the whole elevation from across the road so the pattern reads, then a close-up of the heaviest area with a hand or coin for scale. Efflorescence photographs badly close up and well from a distance; do both.
- Test noted: "brushes off dry; dissolves when wetted": one clause that rules out lime bloom and paint.
- Severity: low for general bloom. Where the pattern points at a detail, split it: keep the cosmetic bloom at low and raise the detail as its own item at the severity a water path deserves.
- Action: dry-brush as it appears, do not wash, review at twelve months. For the split item: inspect the detail named, make good, and confirm at re-inspection that the bloom has not returned there.
The box at the end shows the two-part line. The point of splitting it is that a client reading "cosmetic" on the cill item next year, when the plaster inside is stained, will remember who wrote it.
How to treat it, and what not to do
Do: brush it off with a stiff, dry bristle brush when it appears and again whenever it returns, and let time do the rest. Photograph the extent on each visit; a wall that is fading is doing what it should.
Do not: wash it, pressure-wash it, or seal the wall. Washing carries the salts back in; pressure washing drives water into a wall that is trying to dry; a sealant or water-repellent coating on a wall that is still shedding construction water traps the moisture behind it and can turn a cosmetic bloom into spalling. Acid cleaners belong to the lime bloom problem and to a specialist.
And fix the detail if the pattern found one. The bloom is the messenger; brushing the messenger off the wall every spring for five years is not a maintenance plan. The site inspection checklist has the external details worth checking while you are standing at the elevation, and the snagging inspectors' page shows how the elevation photograph, the close-up and the two-part item go straight into the report from the pavement.
Questions people ask
Does efflorescence go away on its own?
On a new building, usually yes: it is driven by the water used in construction, and once that has dried out, typically within the first year, often after the first summer, there is nothing left to carry salts to the surface. Brush it off dry when it appears. If it is still coming back in the second year, or keeps returning in one place, the water source is not the build and needs finding.
Can I wash efflorescence off?
Not with a hose. Wetting the wall dissolves the salts and carries them straight back into the brick, and they reappear as it dries. A stiff dry brush is the whole treatment for a new wall. Proprietary efflorescence removers and acid washes exist for stubborn deposits, but on new facing brick they can etch or discolour the face, so leave them to a specialist and use them last.
Is efflorescence a sign of damp?
It is a sign that water passed through the masonry, which on a new building is expected. It becomes a damp indicator when it is localised and persistent: a band under a coping or cill, a patch beside a downpipe, a line just above the damp-proof course, or any bloom on the inside face of a wall. Those patterns are reported as water problems, not as efflorescence.
Will the builder fix efflorescence?
Not general drying-out bloom; warranty standards in the UK and elsewhere treat it as a normal temporary condition, not a defect, and the fix is a dry brush. What the builder does have to fix is the defect behind a persistent local deposit, a leaking gutter, an open coping joint, a bridged DPC, which is why the report separates the two.