White Marks on New Paving: What Efflorescence Is and Whether It Goes

Efflorescence is a powdery bloom that sits on the surface and looks worse when the paving is dry. Wet the area with a hose and the colour usually comes back almost to normal, then the white returns as it dries. That test alone identifies it most of the time.

It is typically patchy rather than uniform, often heaviest where the paving stays damp longest, and it appears in the first weeks or months after laying, most noticeably over autumn and winter when the units are wet for long periods.

Things it is not: cement smears from laying, which are hard, feel rough and do not change when wet; limescale run-off from a downpipe, which appears in a run from one point; and paint or plaster splash, which sits proud and is confined to where the work happened.

Yes, in the great majority of cases. Rain and normal use gradually wash the deposit away and the lime available to migrate is finite, so once it has worked its way out it does not come back.

How long depends on the weather and the exposure. A sheltered drive that stays damp can take a full year of weathering. An exposed one often clears in a few months. It is normal for it to look worse before it looks better, particularly through the first winter.

Because it is temporary, the advice we give most often is to leave it alone through the first year. Nothing you do speeds it up dramatically, and some of the things people try make the paving look worse than the bloom did.

Start with the mildest approach: brush the deposit off dry with a stiff brush, repeatedly over a few weeks. A surprising amount comes away that way with no risk at all.

If you want to go further, use a proprietary efflorescence remover sold for concrete paving, follow the dilution on the container exactly, wet the paving first so the product cannot soak in unevenly, work in a small test area out of the way and rinse thoroughly. These products are acid based and used carelessly they etch the surface, dull the colour or lighten the paving unevenly, which is a permanent result rather than a temporary one.

Do not use brick acid at full strength, do not apply on a hot day and do not let run-off reach lawns, planting or a pond. Also avoid sealing paving that is still efflorescing, because a sealer can trap the bloom underneath where nothing will shift it.

Efflorescence cannot be designed out entirely, since it comes from the cement in the units themselves. What good installation does is reduce how long moisture sits in the paving: a free draining sub-base, correct falls so water leaves the surface, and full joints so water is not sitting in gaps all winter.

If you have had new paving from us and a bloom appears, tell us. We will look at it, confirm what it is and advise, and our ten year guarantee covers the installation work behind it.