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How to seal a slate patio

How to seal a slate patio

What’s the best way to seal slate patios?

If you wish to seal a slate patio Floorseal Slate Sealer makes this process easy. Sealing slate is beneficial as it protects the stone, enhances colour, and can create a subtle sheen.

Many darker natural stones, like slate or black limestone, appear more attractive when sealed with a sealer which deepens the colour. This is usually achieved on slate by using a sealer which also produces a slight sheen.

Floorseal Slate Sealer deepens colour and creates a subtle sheen on the surface. This slate sealing product will protect the slate and also inhibit organic growth.

Before sealing your slate pavers or tiles it is important to thoroughly clean the surface. We have produced another more detailed guide which deals specifically with cleaning exterior slate. There is a link to this article at the end of this guide.

How to seal a slate patio

General pointers when pre-cleaning slate

Be aware of issues relating to cleaning and sealing natural slate where brush in compounds have been used. We recommend pre-cleaning your slate with Sealer Residue Remover as a minimum. If you have obvious visible mistakes with brush in compounds you should test, then use Jointing Compound Residue Remover as this is developed to tackle more serious residue issues.

Older patios can be jet washed and Patio Cleaner Plus applied with a sprayer; this will remove any organic contaminations.

For general cement and grout hazes please use Cement & Grout Haze Remover.

Please note that many exterior jointing compounds and grouts are now resin-based NOT cement-based. This is regardless of what they look like or how they have been mixed!

Sealing a slate patio with Floorseal Slate Sealer

Ensure your slate patio is totally dry after cleaning. We also recommend approximately 4 weeks drying and settlement of the stone before sealing the slate.

Floorseal Slate Sealer can be applied via a flat microfibre mop or even by hand using a microfibre cloth. You only need two thin coats which should be applied approximately an hour apart.

It is also possible to apply Slate Sealer with a paint pad or masonry style roller. If you use a roller or paint pad it is important to apply the product in thin coats. You should not see (or leave) any pooling or puddling.

The sealer is quite a heavy white coloured liquid which rapidly becomes clear once applied. This is partly because the sealer is partially absorbed by the slate and also because the sealer contains levelling agents to help produce even coats.

The sealer will dry quickly, and a 2nd coat can be applied approximately one hour later. Keep the 2nd coat thin and even, remember that this coat is now bonding to the first so you will use less product. The 1st coat usually requires a little bit more product, as the stone itself absorbs some sealer, and the 2nd coat will need less sealer.

Applying thick coats or multiple coats on exterior slate is not advisable. Do not assume thick coats or multiple coats (more than 2) are ‘better’; they are not. Usually, thick coats or lots of coats are weaker and more prone to puddling during application.

You will need 24 hours of drying time and curing time when using any form of slate sealer. Please consider the local weather conditions when sealing any exterior stone. If it looks like rain please wait for more favourable conditions.

Other methods of sealing slate

It is possible to seal slate with products which leave a matt finish and still deepen the colour. Natural Stone Colour Enhancer is an impregnator that can be used for this purpose. This sealer can deepen colour without adding a sheen.

This method of sealing is a little more difficult when sealing slate. This is because, even though slate is absorbent, it is quite dense. Slate is compacted mud/silt so it is fine-grained, sealers do not penetrate its surface quite as well as they would a sandstone. This makes using colour enhancing impregnators more difficult due to the need to diligently remove excess product.

Natural Stone Colour Enhancer is the best form of impregnator to use. Impregnators create deeper colours and a matt finish so sometimes are picked in preference to a sealer like Floorseal Slate Sealer. Floorseal Slate Sealer deepens colour and creates a sheen. In other words there are 2 ways of finishing slate, both with plus points. On balance, Floorseal Slate Sealer is probably the easiest of the 2 products to apply.

If you wish to use a matt finish product which deepens colour, please contact us for advice first as it’s slightly more tricky on natural slate. The general links to these products are above highlighted in blue.

How to seal a slate patio

In conclusion

When cleaning work has been carried out you should wait at least 24 hours before any sealing work is planned. Once a 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 or more!

When sealing slate with Floorseal Slate Sealer thin coats are best. Do not assume that thick coats or multiple coats (above 2) are better or more resilient. The opposite is usually the case.

Work in sections and take your time! Never let the product puddle, you can keep spreading the product out with a microfibre flat mop, microfibre cloth or roller. Nice even thin coats will always work the best as application errors are unlikely and the likelihood of pudding is minimal. Always work in dry weather and remember that the curing time is as important as drying time.


Further information


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

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