What Is Efflorescence on Tiles and Brick, and How Do I Remove It?

That chalky white powder appearing on your brick, pavers, or tiled surfaces is called efflorescence — and it's one of the most common complaints tilers and builders deal with across New Zealand. While it looks alarming, it's usually a cosmetic issue rather than a structural one. Understanding why it happens is the first step to getting rid of it for good.

What Is Efflorescence and Why Does It Happen?

Efflorescence is the migration of soluble salts to the surface of a porous material — brick, concrete, mortar, grout, or tile substrate — where they are deposited as a white, powdery or crystalline crust as water evaporates.

Here's the basic process:

1. Water enters a porous material (brick, mortar bed, concrete slab).
2. It dissolves naturally occurring salts within that material.
3. The water migrates to the surface and evaporates.
4. The salts are left behind as a white deposit.

In New Zealand's variable climate — particularly in wetter regions like the West Coast, Northland, and Wellington — moisture movement through building materials is very common. New construction is especially prone to efflorescence in the first one to two years as residual construction moisture works its way out.

Common locations where you'll spot it:

• Brick and block exterior walls
• Concrete driveways and paths
• Tiled patios, pool surrounds, and outdoor pavers
• Grout lines in tiled showers and wet areas
• Retaining walls

Diagnosing the Problem: Is It Really Efflorescence?

Before you start scrubbing, confirm what you're dealing with.

Quick identification test

• Efflorescence is white or grey, powdery or crystalline, and will dissolve or brush away relatively easily. It does not grow.
• Mould or mildew is often black, green, or pink, feels slimy, and may have an odour. It grows in patterns following moisture.
• Lime run (calcium hydroxide leaching from fresh grout or mortar) looks similar to efflorescence but is harder and more glassy in appearance.
• Paint or coating failure may also appear white but will flake rather than powder.

Step-by-step diagnosis

1. Dry-brush a small area with a stiff nylon brush. If the deposit brushes away to a powder, it's likely efflorescence.
2. Apply a few drops of water. Efflorescence will partially dissolve or darken temporarily.
3. Check the source of moisture. Look for leaking gutters, poor drainage, rising damp, or inadequate waterproofing behind tiled areas. Fixing the moisture source is critical — without it, efflorescence will return.
4. Check the age of the installation. New brickwork or fresh tiling within the past 12–24 months is very commonly affected as construction moisture escapes.

What a Homeowner Can Safely Remove Themselves

For light to moderate efflorescence on external surfaces (brick, pavers, concrete), this is generally a safe DIY job. Always wear eye protection and gloves.

Method 1: Dry brushing (mild cases)

• Use a stiff nylon or natural-bristle brush (avoid wire brushes on brick — they can scratch and leave metal deposits that rust).
• Brush the deposits away on a dry day.
• Vacuum or sweep up the residue.
• This works well for fresh, light efflorescence.

Method 2: Water and scrubbing (moderate cases)

• Wet the surface, scrub with a stiff brush, and rinse thoroughly.
• Allow the surface to dry completely before assessing results.
• Repeat if needed.

Method 3: Dilute acid wash (stubborn cases)

For persistent efflorescence, a dilute acid cleaner is effective. Products like Sika efflorescence removers or dedicated masonry cleaners are available at Bunnings and Mitre 10.

Important safety steps:

1. Always pre-wet the surface with clean water before applying acid-based cleaners.
2. Mix according to the manufacturer's instructions — typically a diluted solution.
3. Apply with a brush, allow brief dwell time, then scrub and rinse thoroughly with plenty of water.
4. Never use undiluted hydrochloric (muriatic) acid — it can damage mortar, grout, and skin.
5. Avoid acid cleaners on polished or natural stone tiles (marble, limestone, travertine) — acid will etch the surface permanently. Use a pH-neutral stone cleaner instead.
6. Work in a well-ventilated area and keep children and pets away.

Comparison: Removal methods at a glance

Treating Efflorescence in Tiled Wet Areas

Efflorescence appearing through grout lines in showers or internal tiled areas is a more serious signal. It often indicates that the waterproofing membrane behind the tiles has failed or was never correctly installed, allowing water to penetrate the substrate.

Under the NZ Building Code (clause E3 – Internal Moisture), wet areas like showers must be waterproofed to prevent moisture damage. If efflorescence is appearing through shower grout, simply cleaning the surface won't solve the problem.

Do not ignore internal efflorescence — ongoing moisture movement can lead to tile delamination, substrate damage, and mould growth behind walls.

In this situation, consult a qualified tiler or waterproofing specialist before attempting any repair.

How to Prevent Efflorescence Recurring

Once you've cleaned the surface, take steps to reduce the chance of it returning:

• Seal the surface. Apply a quality penetrating masonry sealer or grout sealer to reduce water ingress. Products from Sika or Ardex are well regarded in the NZ trade. Reapply as per the manufacturer's schedule.
• Improve drainage. Ensure water drains away from walls, paths, and tiled areas rather than pooling against them.
• Fix leaks promptly. Leaking gutters, downpipes, or garden irrigation near walls are common culprits.
• Allow new construction to cure. New brickwork and concrete naturally off-gas moisture for months. Sealing too early can trap moisture — follow the product's recommended cure times.
• Use low-salt materials. When retiling or repointing, ask your tiler to use low-efflorescence mortars and grouts. Mapei and Ardex both offer products formulated to minimise salt migration.

When to Call a Professional

Call a qualified tiler or builder if:

• Efflorescence keeps returning despite cleaning and sealing — this points to an unresolved moisture source.
• You see efflorescence through shower or wet area grout — waterproofing failure is likely and repair involves restricted building work.
• Tiles are lifting, cracking, or hollow-sounding — the substrate may be compromised.
• The affected area is large or on a heritage or character brick building — incorrect cleaning can cause irreversible damage.
• You're unsure whether the white deposit is efflorescence, mould, or something else.

Note: Waterproofing in wet areas is considered restricted building work under the Building Act 2004 in certain situations, and must be carried out or supervised by a Licensed Building Practitioner (LBP). Always check your tiler's LBP registration for wet area work.

You can find qualified, local tilers and waterproofing specialists on tradedirectory.co.nz.

Sources & Further Reading

• BRANZ – Moisture in buildings
• MBIE Building Performance – NZ Building Code
• Sika NZ – Waterproofing and masonry products
• Ardex NZ – Tile and stone installation products
• Licensed Building Practitioners – Find an LBP
• Mapei NZ – Grouts and tile adhesives