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How to clean a slate patio
How to clean a slate patio

Jul 15, 2021

The following guide is a useful how to guide to 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 is less problematic other natural stone.

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 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.

Jointing Compound Residue Remover – Jointing Compound Residue Remover is a strong cleaning & stripping agent specifically used for the removal of obvious resin residues. It is a gel and must be left to dwell for at least 20 minutes to judge its effectiveness on resin-based residues. Please note the removal of obvious resin residues is notoriously difficult. A test patch must be carried out to assess the product’s suitability to remove the resin you have used.

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. 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 that Sealer Residue Remover will not remove heavy obvious stains, smears and rainbowing from resin compounds. In the case of clear and obvious compound marks, please use Jointing Compound Residue Remover – but always test first and allow the test area to dry before committing to the whole area.

Cement & Grout Haze Remover can be used on either new or older patios. For the removal cement-based grouts and cement staining form 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 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 it 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.

If you are planning to seal your slate patio after cleaning (which we would recommend you consider) then we have an article showing how to seal slate patios.

The information included in this article is not exhaustive. But this guide will give you a good start when cleaning exterior slate.

If you need further information please contact Floorseal on (01484) 861461 or email us info@floorseal.co.uk our web address is www.floorseal.co.uk

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