Patio Or Paving Sealer Gone White Or Cloudy

What's happening?

Paving Expert says that most acrylic, polyurethane and silane or siloxane sealants do not get on with water until they have cured, so the whole upper layers of the pavement must be dry before sealing: the paving surface, its interior, the bedding and the jointing. Residual moisture wicks to the surface by capillary action and reacts with the uncured sealant, which shows as blotches, or a cloudy, milky discolouration. It says in the vast majority of cases this is a permanent and irreversible effect that ruins the sealant and the look of the paving. Other causes are the wrong type of sealant for the paving. This is different from efflorescence, a white deposit from the cement, which is the page on white marks on new paving.

What usually causes it?

• Sealing before the paving, bedding and jointing had fully dried
• Rain, dew or a hose wetting the surface before the sealer cured
• Mortar bedding or cementitious or resin jointing that had not cured and dried for at least three days in summer
• Cooler weather, when drying takes longer
• A sealant that does not suit the paving, such as some polyurethane sealants on clay pavers or less porous stone

Is it dangerous?

No. It is cosmetic. Paving Expert says it may mean the sealant needs redoing or replacing sooner than expected.

Can I fix it myself?

First check it is not efflorescence, which is a white powdery or scummy deposit from the cement that can seem to vanish when the paving is wet, as Paving Expert describes. A sealer bloom is milky or blotchy and stays. Paving Expert says that in the vast majority of cases it is permanent and irreversible, so there is no sure home fix. If you reseal, make sure the paving is bone dry first: Paving Expert recommends at least three consecutive bone-dry days in summer and five in cooler months, and following the sealant's own instructions. Check the sealer suits your paving. Everest Paints, a sealer maker, also says sealing should not proceed on saturated substrates or where rain is expected before the sealer cures, and that cleaning chemicals must be rinsed off and the surface allowed to dry thoroughly.

When should you call a driveway and patio installer?

Call a paving contractor when the sealer has failed over a large area or when you are unsure what sealer was used. Paving Expert says the paving must be dry and the sealer suited to the paving type.

What will the driveway and patio installer actually do?

• Identify the sealer and whether the white is bloom or efflorescence
• Advise whether the failed sealer can be dealt with or the paving needs a different approach
• Allow the paving, bedding and joints to dry thoroughly before resealing
• Choose a sealer suited to the paving type
• Reseal when the forecast gives enough dry days

Who fixes this

• Patio cleaning and resealing

Questions people ask

Sources & References

1. Paving Expert: when sealants go wrong
2. Paving Expert: efflorescence
3. Everest Paints: block paving sealers, preparation and moisture