Before Washing Brick, Check the Wall and Mortar

Start with the wall's condition

Before washing a clay-brick wall, check the brick and mortar condition, known treatments and signs of water entry. These findings help determine whether cleaning should proceed and which professional or manufacturer advice is needed.

This reference concerns existing clay-brick walls. Stone, concrete block, painted masonry, brick-slip systems and brick paving need their own material-specific plan.

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Check joints before adding water

The National Park Service warns that even water-based cleaning can harm historic masonry. It calls for sound mortar joints and a watertight building before water cleaning; badly deteriorated masonry may be made worse by water.

Our practical advice: if joints are missing or crumbling, brick faces are deteriorating or water is entering the building, pause the proposed wash for a qualified masonry assessment. A cleaning quote does not replace that assessment.

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Separate construction cleanup from an existing wall

The Brick Industry Association distinguishes removing construction residue from treating stains on an existing wall. Its Technical Note 20 identifies prior water repellents, coatings and other unexpected conditions as reasons to obtain professional guidance when they interfere with cleaning.

Ask about previous treatments and repairs before borrowing a method intended for newly laid brick. Record what is known and what still needs checking.

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Do not choose a method from a pressure label

Wienerberger's UK guidance advises against high-pressure brick washing because brick surfaces and mortar joints can be damaged. It recommends specialist assessment for historic brickwork and expert help for extensive or hard-to-identify stains.

BIA's current FAQ allows that pressurized cleaning is appropriate for certain brick types, while warning of irreversible damage if used incorrectly. These positions do not establish a safe setting for your wall. Obtain the applicable brick manufacturer's guidance and a plan for the actual material and condition.

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Agree on a trial and how to judge it

Once the wall is considered suitable for cleaning, BIA recommends trial work and assessment of both brick and mortar after drying. A wet patch alone is not the finished result.

For historic work, NPS calls for separate tests of different materials and finishes, complete drying and, where feasible, extended weathering before final evaluation. Involve preservation expertise rather than treating a small patch as permission for the whole building.

Agree with the contractor on the intended result, the trial's review and any areas excluded from work. The cited documents are technical, preservation and manufacturer guidance, not a universal cleaning specification or a new legal requirement.

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