Brick and stone cleaning

Algae, mould and organic staining removed from brickwork, sandstone and limestone at low pressure without eroding the face or washing out pointing.

In short: Brick and stone soft washing removes algae, mould, lichen and organic staining from brickwork and natural stone using a biocide at low pressure, so the face of the masonry and the pointing are not eroded. It suits homeowners with green or black stained walls and older or soft masonry. In the UK, prices are typically £4 to £8 per m², or about £300 to £1,100 for a house.

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Brick and natural stone look solid, but many are surprisingly soft. Handmade and older bricks, sandstone and limestone can lose their fired skin or weathered face to a pressure washer in seconds, and once that is gone the masonry absorbs more water and weathers faster. Lime mortar in older buildings is softer still and can be washed out of the joints.

Soft washing avoids that damage by killing organic growth chemically and rinsing at low pressure. It deals well with green algae, black mould and lichen. It does not remove every kind of staining: efflorescence, rust, paint, carbon deposits and mineral staining are not organic, and may need specialist masonry cleaning methods. Listed buildings may need consent before cleaning, so check with your local council if your property is listed.

What is included

Assessment of the brick or stone type, condition and pointing
Identification of organic and non-organic staining
Pre-wetting of the masonry and protection of nearby plants
Low-pressure application of a biocide suited to the material
Gentle rinsing that does not erode the face or the joints
Treatment of garden walls, plinths and steps in the same material
Advice on any staining that needs a different method

Who it is for

Brick houses with green algae on shaded elevations
Sandstone and limestone with black or green organic staining
Older properties with soft bricks or lime mortar
Garden walls, steps and boundary walls in brick or stone
Owners who want to avoid the damage high pressure can cause

How much does it cost?

As a guide, brick and stone soft washing typically costs £4 to £8 per m². A full house elevation usually falls between £300 and £1,100 depending on size, height and how sensitive the masonry is. See our full cost guide.

How it works

How brick and stone cleaning works, step by step

Identify the masonry

The type of brick or stone, its condition and the mortar are checked, and a test area is cleaned if needed.

Pre-wet

The masonry is wetted first so it absorbs less solution, and plants and adjoining surfaces are protected.

Treat gently

The biocide is applied at low pressure and given time to work on the organic growth.

Rinse and review

The wall is rinsed at low pressure and any remaining non-organic staining is pointed out.

Brick and stone cleaning: FAQs

Will soft washing remove white marks on my brickwork?

White, powdery or crusty marks are usually efflorescence, which is salts carried out of the masonry by moisture. It is not organic, so a biocide does not remove it. It often brushes off when dry and fades as the wall dries out. Persistent efflorescence suggests ongoing moisture, which is worth investigating.

Can you clean a listed building?

Cleaning the exterior of a listed building can affect its character and may need listed building consent, depending on the method. Contact your local council's conservation officer before booking. Gentle, low-pressure biological cleaning is often viewed more favourably than abrasive or high-pressure methods, but the decision is the council's.

Is soft washing safe for lime mortar?

Low-pressure soft washing is much kinder to lime mortar than pressure washing, which can wash soft mortar out of the joints. The solution strength is kept appropriate for the masonry and the wall is rinsed gently. If the pointing is already loose or crumbling, it may need repointing regardless of cleaning.

Why is my stone wall black?

Black staining on stone can be organic, such as black algae and lichen, or it can be carbon deposits from historic pollution, which are bonded into the surface. Organic staining responds to soft washing. Old carbon crusts usually need specialist methods such as low-pressure steam or poultices, so a test area is a sensible first step.