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How-to Guides

How to clean a slate patio

How to clean a slate patio

The best way to clean slate patios

The following guide is a useful how-to guide for cleaning slate patios, pavers, and slabs. It can also be used as a reference when cleaning slate walls, tables & fireplaces etc.

Slate is not sensitive to acids nor alkaline solutions so it is less problematic than other natural stone types.

This guide should be used as a starting point before sealing your slate patio. There are some subtle differences between cleaning interior slate floors and exterior patios. These differences are covered in another article.

If you are attempting to remove old sealers, we advise contacting us first as it is quite challenging!

General advice regarding slate cleaning products

How to clean a slate patio

Before sealing slate pavers or tiles it is important to clean the surface. Cleaning products are often used for a specific purpose, perhaps the removal of cement, grout, or organic contaminations. You need to select the correct one, you may even need a combination of cleaners.

Pre-cleaning your slate patio

The product you select to clean a slate patio will vary depending on the contamination, and whether the slate is a newly laid or an older existing slate patio. The products below are all typically used on exterior slate patios, paths & pavers.

Cement & Grout Haze Remover – This product is for the removal of cement-based grouts or general cement. It will not react with the slate itself just the cement-based materials on the surface. Please note: Cement & Grout Haze Remover will not remove resin-based exterior grouts or resin-based brush in compounds – Keep reading!

Sealer Residue Remover – This product is used to carry out a general pre-clean of exterior slates, it will attack the thin film of resin that may have been left when using resin-based grouts or brush in compounds. Sealer Residue Remover can also be used to remove excess impregnating sealers and old water-based acrylic topcoat sealers. This product is typically used on new slate patios.

Patio Cleaner Plus – Floorseal Patio Cleaner Plus is a fantastic cleaning product which is typically used to clean older slate patios of organic contaminations. It will remove black spot lichen, algae, slimes, fungi, and bird droppings. This product is a versatile cleaning agent which is used 1:1 with clean water (apply with a pump sprayer). It can also be used neat on severe staining and heavy organic build-ups as well as dirt and grime.

Efflorescence Remover – Removes general salting and staining on the surface of slates. Efflorescence can appear shortly after laying or after wet weather.

Cleaning your new slate patio

When cleaning a new slate patio, we recommend using Sealer Residue Remover to clean the surface and to remove the resin slick which can be present around the joints. Many patios are jointed with brush-in style resin compounds, so Sealer Residue Remover is the obvious choice to pre-clean with. Please note some 2-part resins or severe resin staining may not be possible to remove via a cleaning fluid!

Cement & Grout Haze Remover can be used on either new or older patios. Please note it is designed for the removal cement-based grouts and cement staining from traditional mortars or grouts.

Please note it is beneficial to pre-wet the surface of your slate patio before using a cleaning agent. We always recommend really rinsing the surface off afterwards as well to ensure all cleaning products are fully removed before any further work is carried out.

How to clean a slate patio

Cleaning older slate patios

To pre-clean an older patio we recommend Patio Cleaner Plus to remove dirt, grime, lichens, algae, and other organic contaminants.

It is unlikely you will need other cleaning agents unless you have been replacing old jointing materials with new.

After cleaning with Patio Cleaner Plus lots of rinsing off will be required – and a good jet wash!

If you are going to strip old sealers, please contact us this can be quite involved. It is often difficult to identify the old sealer unless you have a container left over. There are ways of doing this, but it is beyond the scope of this article.

Removing Efflorescence

Efflorescence is just a powdery residue left on the surface as moisture evaporates which leaves a salt behind. It can be washed away with water, but stubborn marks may require a cleaner.

Efflorescence can occur on new or older patios and is not usually serious. Salting can occur over days, weeks, or months but usually, it runs its course and does not return.

Efflorescence can occur just after pavers are laid as the base dries out. It also often appears after a period of wet weather early in the year.

How to clean a slate patio

In conclusion

When cleaning work has been carried out you should wait at least 24-48 hours before any sealing work is planned. Once a slate patio has been washed down with water, cleaning solutions applied, rinsed off and probably pressure washed the slate may take some time to dry – possibly 48 hours!

It is good practice to thoroughly rinse the patio after cleaning solutions have been applied. For this reason, you will use a reasonably large amount of water so drying times can be slow. Damp patches may be noticeable in the joints, particularly if they are sand and cement up to 24-48 hours after cleaning.


Further information


Please Click Here to view all our products & accessories for cleaning and sealing slate. This includes all our handy ‘how to’ guides for cleaning and sealing interior and exterior slate.

The information included in this article is not exhaustive. If you need further information please contact Floorseal on (01484) 861461 or email us our web address is