Efflorescence is the white or grey powdery staining that appears on brick, block, render, and concrete. It forms when soluble salts dissolved in water migrate to the surface and crystallise as the water evaporates. On new builds it often disappears on its own within the first year or two. On older properties it can be a sign of persistent water ingress that needs addressing before the cosmetics.
The good news is that the deposit itself is rarely damaging. The bad news is that it keeps coming back until you deal with the source of moisture.
What Causes Efflorescence?
Water is always the root cause. It dissolves naturally occurring salts in the brick, mortar, or backing material and carries them to the surface. Common triggers include:
- New construction drying out — freshly laid brickwork holds a lot of moisture; efflorescence in the first 1–2 years is almost always benign.
- Driving rain penetration — facing brickwork that gets saturated on a regular basis will effloresce repeatedly.
- Rising damp — groundwater wicking up through an absent or failed damp-proof course brings calcium and sulphate salts with it.
- Leaking gutters or downpipes — concentrated water running down a wall saturates a localised patch.
- Poor pointing — open or eroded mortar joints let water in rather than shedding it.
- Condensation in cavity walls — less common but possible with poor cavity insulation detailing.
How to Diagnose the Severity
Before reaching for the cleaning brush, identify what you are dealing with:
- Superficial bloom — thin white haze, appears in spring/summer, no damp indoors, mortar joints intact. This is almost certainly benign first-year efflorescence. Monitor it.
- Persistent staining — reappears within weeks of cleaning, same patch. Investigate gutters, downpipes, pointing, and window sills above.
- Cryptofluorescence (sub-surface) — salts crystallise beneath the brick face and cause the surface to spall. This is more serious and usually indicates prolonged saturation. Professional assessment is advisable.
- White tide-mark at low level — rising damp pattern. Check whether a DPC is present and intact.
[!warning] When to call a professional If efflorescence is at low level (below 1 m), if internal plaster shows damp or staining, or if the brick face is spalling, get a damp specialist or structural engineer to assess before you spend money on surface treatments.
How to Remove Efflorescence: DIY Methods
For the majority of cases — dry, powdery surface deposits on otherwise sound brickwork — removal is straightforward.
Dry brushing (first attempt) Use a stiff-bristled nylon or natural fibre brush (not wire on softer handmade bricks). Brush vigorously when the wall is fully dry. Collect and dispose of the dust rather than hosing it into joints. This is the correct first step; applying water too early can push salts back in.
Dilute acidic wash (stubborn staining) A 5–10% solution of white wine vinegar in water, or proprietary efflorescence remover (phosphoric or hydrochloric acid-based), applied with a stiff brush:
- Wet the wall with clean water first to prevent the acid soaking too deep.
- Apply the solution and allow to dwell for 5–10 minutes.
- Scrub and rinse thoroughly with clean water.
- Neutralise with a dilute bicarbonate of soda solution if using hydrochloric acid products.
Always test on an inconspicuous area first. Acid treatments can bleach or etch softer limestone-based mortars and some brick types.
Pressure washing Effective but use with caution — high pressure can erode soft mortar joints and cause more problems than it solves. Keep pressure below 1,200 psi and use a fan tip at an angle, never straight on.
Preventing Recurrence
Cleaning removes what is already there; prevention stops it coming back.
- Repoint open or eroded joints with a mortar matching the original specification (a harder OPC mortar on a lime-mortared Victorian wall will cause cracking and more damp).
- Repair gutters and downpipes — a blocked gutter can deposit hundreds of litres of water per hour onto a wall.
- Check window sill overhangs and sill flashings — water should drip clear of the wall.
- Apply a breathable masonry water repellent — silane/siloxane-based treatments (not paint or film-forming sealers) allow moisture vapour out while repelling liquid water. These last 10–15 years when correctly applied.
- Address DPC failure if rising damp is the cause — remedial DPC injection costs £500–£2,000 depending on wall length and method.
Cost Summary
| Task | DIY Cost | Contractor Cost |
|---|---|---|
| Dry brush (tools only) | £0–£15 | n/a |
| Dilute acid clean, 1 elevation | £10–£30 (materials) | £150–£400 |
| Pressure wash, 1 elevation | £50–£100 (hire) | £100–£250 |
| Full-house chemical clean (contractor) | — | £300–£800 |
| Silane/siloxane water repellent (contractor) | £30–£80/litre (DIY) | £400–£1,200 (full house) |
| Repointing (contractor, per m²) | — | £25–£55/m² |
| Remedial DPC injection | — | £500–£2,000 |
All prices are indicative 2026 ranges inclusive of VAT.
Building Regs and Standards
Efflorescence itself is not a Building Regulations matter, but the underlying causes often are. Where damp penetration is linked to a defective DPC, this falls under Part C of the Building Regulations (Site preparation and resistance to contaminants and moisture). Any DPC repair or replacement should comply with BS 8215:1991 and, where injection systems are used, the BBA certificate conditions of the chosen product.
When to Call a Professional
Bring in a qualified damp surveyor (CSRT or CSSW qualified via PCA) if:
- Efflorescence keeps returning to the same patch despite cleaning and obvious repairs
- You see brick face spalling or cryptofluorescence
- Internal walls adjacent to the affected area show damp, staining, or mould
- You are buying a property and want an independent view
An independent damp survey typically costs £150–£400 and is worth every penny before committing to expensive remedial works. Be aware that some damp-proofing contractors have a commercial interest in recommending work — an independent RICS-qualified surveyor will give you an unbiased opinion.
Summary
Efflorescence on brick is common, often cosmetic, and usually manageable with a stiff brush and patience. The key questions are whether it is recurring, whether there is associated spalling, and whether there is any internal damp. Answer those first, fix the source of moisture, then clean. Doing it the other way round is expensive and temporary.
