Brickwork turning white in colour

Noel Larkin answers a readers question published in the Irish Times March 31st 2016

In my new home, which I purchased last year, I notice the brickwork is beginning to turn white in colour. Can you explain what this is, and what is the remedy to return it to its original colour?

A The issue you describe is very common and is known as efflorescence. The crystallisation of water-soluble salts can often result in a harmless white powder or crystals on the surface of brickwork. Water, usually introduced during construction, slowly dries to the surface of the wall bringing natural salts with it. It is generally recognised that it can take up to 12 months for a new house to fully dry out.

It is not unusual during this initial drying period that salts contained within the brickwork are carried to the outer wall surface. This results in the white powdery discolouration you describe. In most cases, the natural clay used to form the brickwork is the source of the salts, but the ground on which the building is constructed can also contribute. The cement mortar used to hold the bricks together can in some cases react with the clay bricks and lead to efflorescence.

In some cases, the problem of efflorescence can be exaggerated if brickwork is allowed to become excessively wet during the construction phase. This is why it is important that brickwork is covered when delivered to site. Brickwork must also be protected from rain at the end of each working day during building.

The orientation of your house, the extent of exposure to driving rain and the porosity of the brick can also have an influence. On occasion, leaking gutters or downpipes can also lead to saturation of the brickwork. Subsequent drying-out of the masonry promotes the migration of salts to the surface, resulting in white staining.

You should try to establish if there is any apparent source of moisture allowing the wall to become excessively wet. If no such source is apparent, you can assume the efflorescence is being generated by drying-out of water used during the construction phase of your house. It can therefore be anticipated that once the initial drying of the walls has ceased, the efflorescence can simply be cleaned down.

The white crystals are usually easily removed, revealing the original brick. I would avoid using water as this can simply wash the salt back into the wall. The bricks may look clean but the same salt slowly reappears to the surface. Chemical washes and more extreme sand blasting should be avoided as these can do more harm than good. Surface efflorescence can normally be removed by wire brushing.

Noel Larkin is a chartered building surveyor and member of the Society of Chartered Surveyors Ireland,