How to seal York stone flags & pavers

This article explains how to seal a York flagstone floor. This relates to cleaning original interior Yorkshire sandstone flagged floors, re-laid reclaimed floors, sand/media blasted York floors and exterior York sandstone pavers. We would recommend you clean/prepare the stone prior to sealing, there are links to other articles regarding cleaning & sealing York stone at the foot of the page.

There are always subtle differences between sandstones. Even though many sandstones have been grouped together and collectively given the title of ‘York stone’ they may differ. Usually, the same cleaning and sealing advice can be applied to most types of sandstone.

The appearance of very old Yorkshire sandstone flags is different to a more recently quarried York stone. They can often be treated in the same way as they have similar characteristics despite older slabs being worn/weathered.

If you wish to view the product pages of any of the products mentioned in this article, please click the product title highlighted in blue. There is other information at the foot of the page regarding user guides and other how to guides.

What should I seal Yorkshire sandstone with?

We believe the best type of sealer for York stone is a breathable impregnating sealer. It may be possible to use other forms of (colour altering/enhancing) sealers on some Yorkshire sandstone flags – with care!

The first (and recommended) option is Floorseal Natural Stone Sealer Breathe which is a non-visible fully breathable impregnator. We recommend using this sealer to seal almost any form of York stone slab – new or old. It will not alter the appearance of the stone after treatment and can be applied in listed/historic buildings. This product can be applied to interior & exterior surfaces.

If you do wish to seal with an appearance/colour altering sealer we have two options –

Stone & Tile Sealer Satin – A water-based semi-breathable topical sealer which creates a sheen and may slightly deepen colours. This product should be applied twice and can be applied in further coats to increase sheen. Often used on sandstone, slate or brick flooring but can be used on a stone surface that is dusty or chalky. We do not recommend application to pale limestone and highly polished stone. This product may create subtle colour enhancement. Indoor use only.

Flagstone Sealer – A solvent-based topical semi-breathable sealer which creates a silk finish and significantly deepens colour. This product should be applied twice. Often used on sandstone, slate or brick flooring but can be used on a porous surface which is dusty or chalky and would benefit from colour enhancing. We do not recommend application to pale limestone or highly polished stone. Interior or exterior use.

Old interior Yorkshire sandstone flags are a little different & fall into 3 main categories

• The first being floors which have been laid and never disturbed (usually on lime).
• The second category is made up of old flags which have been uplifted and re-laid with a damp-proof membrane and repointed with modern pointing.
• The third category could be either of the above but a floor which has been sand/media blasted.

The application of a sealer will make the surface of this kind of York stone resistant to water and oil-based staining (On exterior flags this in turns helps to prevent organic growth and frost damage).

How to seal old undisturbed original interior Yorkshire sandstone flags

Floors that have never been disturbed are usually obvious due to how the slabs have been laid edge to edge. This method of laying the slab is known as monolithic fixing. There is no real pointing material between the slabs, sometimes none.

At the time of fixing the slabs, a little of the lime screed underneath may have been pushed up to fill some gaps. Sometimes gaps between the slabs have appeared over time due to settlement.

Old, flagged floors will not have a damp-proof membrane (unless added later).

Not having a damp-proof membrane is not necessarily an issue. Many old floors are perfectly dry. Floors which are damp have often become softer over time, the surface can be de-laminating or displaying efflorescence.

We usually recommend sealing with an impregnating sealer such as Natural Stone Sealer Breathe. This is because older York stone floors may have vapour passing through and also because older floors are often marked, stained, or impregnated with a variety of chemicals. This staining can be accidentally enhanced by using a traditional colour enhancing sealer, thus creating a patchy appearance. This is why we avoid using traditional colour enhances on older flagged floors.

The level of porosity within the stone can vary due to natural mineral content/veining. Variances in porosity can also be created by contaminations of old paints, bitumen, oil, old sealers & some cleaning products. This is why the final patchy appearance, which some colour enhancers accidentally create, occurs. Older Yorkshire sandstone floors are also often grey in colour, so are less responsive to colour enhancing regardless.

For the majority of old undisturbed York stone floors, we recommend sealing with Floorseal Natural Stone Sealer Breathe. It is the best way to seal an old York sandstone floor. This is achieved without altering the colour, thus retaining the natural appearance of the stone and avoiding patchy appearance issues.

Old Yorkstone floors often have visible contaminations, this includes re-laid or reclaimed York Stone floors. This is a good reason to use invisible impregnating sealers like Natural Stone Sealer Breathe, as there is no possibility of a problem with patchy colour enhancement due to contaminants.

Sealing re-laid or reclaimed interior Yorkshire sandstone flags

The information in the preceding paragraphs also applies to re-laid York stone flagged floors. The only significant difference is a re-laid floor will usually have a damp-proof membrane (DPM). It is unlikely a re-laid floor will have been fitted without a DPM.

The pointing is usually a Portland cement and sand mortar, which is semi-breathable. In contrast, lime pointing will allow all moisture vapour through, so fully breathable. Many builders will avoid lime pointing, if a DPM has been applied, since breathability is generally no longer important. But also because lime is also more difficult to work with if you are not familiar with working with it!

The width of the pointing in re-laid floors is more likely to be 25mm (rather than historic almost non-existent pointing lines). Fashions change, people like wider joints and builders find them easier to point!

We recommend sealing re-laid Yorkshire sandstone flags and pavers with Floorseal Natural Stone Sealer Breathe. This sealer does not alter the appearance of the stone, and allows moisture vapour transmission but resists water and oil-based staining.

How do I seal a sandblasted Yorkshire sandstone floor?

Possibly with some difficulty, as the surface will be very porous and prone to staining!

The difference between an old sandstone and a recently blasted floor is that the older floor will have been subject to wear. Sandblasted floors are lighter in colour and more porous.

Yorkshire stone is quite coarse and will, over time, wear with foot traffic. They also pick up dirt and contaminations of old sealers and cleaning agents. Older floors seem less prone to staining due to the fact they have become a deeper colour with less porosity present.

If you sand/media blast a floor the surface lightens in colour and becomes more ‘open’ and porous – it is actually a much rougher surface.

The best way to seal a sandblasted surface is with an impregnator  and possibly with a topical seal over the top (a bit more difficult to get right). Make sure you saturate the surface. The coverage rates of most sealing products (regardless of brand) are not relevant as the porosity will be greatly increased.

Our best advice is to really saturate the surface applying the product twice approximately an hour apart. It is notoriously difficult to fully seal a sand blasted York stone floor. But saturation with an impregnating sealer, with care, should seal the surface.

The location of the floor is also a factor i.e. a busy kitchen or hallway has the potential to become stained than a room with less traffic.

You can seal with Floorseal Natural Stone Sealer Breathe & possibly overcoat with Floorseal Stone & Tile Sealer Satin.

Sealing newly laid/quarried exterior York stone

When sealing newly laid ‘new’ sandstones i.e. York Stone which has been recently quarried you should use an impregnator.

Floorseal Natural Stone Sealer Breathe is suitable for sealing any type or age of sandstone. This is our recommended sealer to seal every type of York sandstone, regardless of colour or age.

It is the easiest and safest way to seal a newly quarried (and light coloured) York sandstone.

In conclusion

Natural Stone Sealer Breathe – A fully breathable water-based sealer that resists water & oil-based staining. It does not change the appearance of the surface it is applied to. Once sealed, the surface still retains an unaltered natural finish. It is to be applied twice with all excess product removed after each application. Suitable for new or older surfaces (possibly in listed buildings) which may not have a damp-proof membrane (DPM). Suited to sandstones, general flagstones, pale limestones and other porous surfaces. Interior or exterior use.

Stone & Tile Sealer Satin – A water-based semi-breathable topical sealer which creates a sheen and may slightly deepen colours. This product should be applied twice and can be applied in further coats to increase sheen. Often used on sandstone, slate or brick flooring but can be used on a stone surface that is dusty or chalky. We do not recommend application to pale limestone and highly polished stone. This product may create subtle colour enhancement. Indoor use only.

Flagstone Sealer – A solvent-based semi-breathable topical sealer which creates a silk finish and significantly deepens colour. This product should be applied twice. Often used on sandstone, slate or brick flooring but can be used on a porous surface which is dusty or chalky and would benefit from colour enhancing. We do not recommend application to pale limestone or highly polished stone. Interior or exterior use.

Test all products before use.

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

Please note there are other products which can be used on your interior/exterior floors which may also be suitable. We stock sample sizes of our sealing products, these are available from the individual product pages under the select size options.

 The information included in this article is not exhaustive. If you need further information please contact Floorseal or email info@floorseal.co.uk