Gentlest effective method

Heritage Brick Cleaning

Heritage masonry does not need a stronger clean. It needs a slower one. The guiding principle in conservation work is the gentlest method that achieves the result, and on a hand-made brick wall with lime mortar that rules out almost everything a modern cleaner would reach for first.

Think Brick accredited
Fully insured
20+ years experience

Think Brick accredited

Fully insured

20+ years experience

Illawarra to the Highlands

Quick answer

How should heritage brickwork be cleaned?

Heritage brickwork should be cleaned using the gentlest effective method — typically low-pressure water, nebulous misting, poultices or fine micro-abrasive systems rather than hydrochloric acid or high pressure. Hand-made bricks have a soft fired skin and are usually laid in lime mortar, both of which acid and high pressure erode irreversibly. Testing on a discreet trial patch before any full-scale work is standard conservation practice.

At a glance

Acid: Avoided — damages lime mortar & fired skin
Pressure: Low, typically under 500 psi
Standard practice: Trial patch before full works
Suitable for: Churches, halls, cottages, warehouses

Why old brick is a different material

A hand-made or early machine-pressed brick has a fired outer skin that is denser and more weather-resistant than the body underneath. Once that skin is stripped — by acid, by grit blasting, or by a turbo nozzle — the soft interior is exposed and the brick starts to erode and spall. It cannot be put back.

Lime mortar behaves differently again. It is deliberately softer than the brick so the joint sacrifices itself instead of the unit, and it allows the wall to breathe. Hydrochloric acid dissolves it quickly, and modern hard cement repointing traps moisture and pushes decay into the brick face.

What we use instead

The method is chosen for the soiling and the substrate, and it is always tested first on a discreet area.

Low-pressure and nebulous water washing — extended fine misting to soften carbon and soiling without mechanical force.
Poultices — a chemical or absorbent medium held against the stain to draw it out of the masonry rather than driving it deeper.
Fine micro-abrasive systems at controlled low pressure with soft media, where wetting is not appropriate.
Biocide treatment for lichen, algae and moss, allowing the growth to die back and release rather than tearing it off a fragile surface.
Targeted spot work on graffiti, paint and iron staining rather than treating whole elevations.

Buildings we work on

Late-nineteenth and early-twentieth century cottages and terraces, churches and parish halls, former warehouses and industrial buildings, sandstone-and-brick civic buildings, and the older brick housing stock across Bowral, Moss Vale, Berry, Kiama and central Wollongong.

Where a property is heritage-listed or in a conservation area, we are happy to work to a conservation management plan and to a heritage consultant’s specification.

Coverage

Where we do heritage brick

Illawarra

Wollongong · Shellharbour · Albion Park · Dapto · Kiama · Shell Cove

Shoalhaven

Nowra · Bomaderry · Vincentia · Huskisson · Berry · Culburra Beach · Ulladulla

Southern Highlands

Bowral · Mittagong · Moss Vale · Bundanoon

Sutherland Shire

Helensburgh · Engadine · Sutherland · Cronulla

Based at Warilla. Everything from Helensburgh to Ulladulla and inland to the Southern Highlands is inside our normal working area.

FAQ

Heritage Brick — questions we get asked

Can you acid wash a heritage brick building?

In almost all cases you should not. Hydrochloric acid attacks lime mortar far faster than it cleans the brick face, and it can permanently discolour hand-made brick. Where any acidic treatment is used on historic fabric it is a mild, targeted, tested application, not a wash of the whole elevation.

Will sandblasting clean my old brick house?

It will strip it. Sandblasting removes the fired skin along with the dirt and leaves a rough, open surface that absorbs water, grows moss and decays much faster than before. It is one of the most damaging things that can be done to historic brickwork and it is not reversible.

Do you provide a trial patch?

Always, on heritage work. A test area lets us confirm the method, the dwell time and the finish before it is committed to an elevation, and it gives the owner or consultant something concrete to approve.

Keep reading

Need heritage brick quoted?

Call 0448 882 780 or send photos through the quote form. We will tell you what the job needs and what it will cost, including when the honest answer is that you do not need us.

0448 882 780 Free quote