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This guide explains how to clean and renovate a York stone floor. Many of the principles noted apply to floors as well as walls and lintels. You can apply many of these techniques to both interior and exterior floors/walls.
York stone, also known as Yorkshire sandstone, can be old flags or newly quarried pavers. There are some differences between cleaning older interior Yorkshire sandstone flags and newly laid exterior flags.
Very old York stone flags, which have never been disturbed, are monolithically fixed. There are virtually no gaps between the slabs and will not have a damp-proof membrane (DPM).
Old slabs which have been uplifted and re-laid often have a wider gap between the flags. Typically, this gap is 25mm wide and will have been pointed with a Portland sand & cement mortar (some exterior flags may have joints with a resin-based brush in compound)
If the joint is very narrow, almost non-existent, the pavers will be original, and it is unlikely they have been disturbed/uplifted.
If you wish to view the product pages of any of the cleaners 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.
The condition of your York stone flags or pavers will affect the overall success of any cleaning work. Yorkshire sandstone flags which have been buried under screed or bitumen may need additional work beyond general cleaning.
Badly stained flags or flags which have become soft and are de-laminating could require sand/media blasting to renovate them. This may also be the case if multiple layers of polyurethane varnish have been applied. There are some advanced cleaning/stripping techniques which can remove varnish but are beyond the scope of this article.
Generally, grime, dirt, and some old sealers can be removed. Organic contaminations growing on exterior pavers, walls or lintels are usually possible to clean off. The effects of weathering, long-term organic contaminations, or other staining may not always be possible to remove. Testing with different types of cleaners is advisable when dealing with old badly marked stone.
If you are deep cleaning an interior York stone floor, we recommend Floorseal Stone Floor Cleaner.
Stone Floor Cleaner is very effective at removing built-up grime and dirt. A dilution rate of 1:5 is the usual ratio of product to water.
Stone Floor Cleaner is effective when cleaning old interior Yorkshire sandstone flag floors. Floors which have darkened & become grimy over a long time can clean up with a little effort.
Stone Floor Cleaner can be applied via brush or mop & bucket. Alternatively it can be used in conjunction with a slow speed rotary & wet pick-up vacuum.
After use, always rinse the surface with plenty of clean water. It can be beneficial to add a small amount of neutralising agent to your rinse water, to neutralise the cleaning solution. This means adding a small amount of an acidic solution, such as a white wine vinegar, or Floorseal Cement & Grout Haze Remover. The agent can be quite weak, so it does not effect the stone.
You will only need 50ml to 100ml (added to 5-10 litres of water) of acidic solution to neutralise.
Rinsing with just clean water may be effective at neutralising cleaning agents. This method of neutralising may be adequate providing you rinse the floor a few times with plenty of water.
When neutralising a cleaning agent on acid-sensitive surfaces like limestone, travertine, or marble etc you should just heavily rinse the area with clean water NOT an acidic solution.
When working (in awkward areas) up to walls, corners, or kitchen units, you can apply/agitate Stone Floor Cleaner using a stiff hand brush, then blot/rinse off the area with clean water. The cleaning solution can be blotted from the surface with a microfibre cloths.
Microfibre cloths can also be used to damp wipe skirting boards, doors, kitchen units & other adjacent surfaces after cleaning work is complete.
Black Spot Remover Plus is suitable for cleaning exterior York stone. This product can be applied undiluted for the removal of organic contaminations like green algae and black spot lichens on horizontal or vertical surfaces.
Black Spot Remover Plus will also remove general dirt, certain oils, bird droppings & other organic contaminations.
This product can be used in conjunction with Floorseal Cleaner Additive. Cleaner Additive is a thickening/foaming agent which inhibits premature drying and helps the remover stick to vertical surfaces.
Pressure washing can be effective when cleaning exterior York stone floors. This will remove many forms of contamination, except for black spot lichen. Use Floorseal Black Spot Remover Plus to remove black spot lichens and for general deep cleaning. You do not have to use a pressure washer when using Floorseal Black Spot Remover Plus, but it can be useful when rinsing.
To successfully treat interior lintels or mullions which are suffering from black mould we recommend Floorseal Stone Pro. This product will remove almost any form of organic growth. Stone Pro is typically diluted at 1:1 and comes complete with a small hand sprayer. The solution can be used in a more dilute form (than the standard 1:1) if required.
Apply carefully with the hand sprayer provided. The solution can also be applied with a paint brush if required. You can rinse the surface after use, but often this is not required when treating smaller areas such as interior mullioned windows.
Floorseal Stone Floor Cleaner will remove most water-based emulsion paint (with adequate dwell time). We have found that soaking paints with just water, in conjunction with a small amount of Stone Floor Cleaner works well. The dwell time (time left to soak) is critical as it can take a while for the solution to emulsify paints. Adding more solution and water will often be required during the dwell time to keep the surface wet.
If the sandstone is honed (relatively) smooth, a flat sharp scraper can be useful. For rougher riven York sandstones, a stiff hand brush can be useful. It is also possible to use a narrow brass handheld brush. Brass brushes are softer than normal steel/wire brushes, so possible to use without marking the stone. You should still always take great care when using anything abrasive, even on rough flagstones.
Overall long dwell times (soaking for long periods of time) is the most effective method of removing water-based paint.
Solvent-based products for oil-based paint removal are also available. We have found that they can lead to solvent staining so you should take care when using solvent-based cleaners/strippers/thinners. Solvent/oil-based paint staining can be very difficult to remove, long soak/dwell times are often beneficial. It depends on how badly marked the surface is.
Some oil marks are possible to remove with Floorseal Stone Floor Cleaner. You will need to use lots of dwell time i.e. soaking.
Oil marks are always hard to remove due to being held deep within the stone and may have oxidised. There are methods to remove oils using poultices, but this is beyond the scope of this article. Poultices often fail, but can be used overnight to draw deep stains out from within the stone.
For context, a poultice is a powder which is mixed with Floorseal Stone Floor Cleaner and then applied to the stain. Cover the stain with a thin plastic sheet and tape it to the floor. Puncture the plastic numerous times, as the powder dries, the stain removing solution (after having penetrated the stain/stone) dries slowly pulling the stain out from within the stone.
Be aware some oil stains will not respond; you could also create a halo in the stone from where the poultice was applied!
Our preferred method (when cleaning interior York sandstone flags) was to use Floorseal Stone Floor Cleaner. This would remove most, if not all general dirt & oil marks, we would then consult with the customer over any further specialist oil removal work which might be required.
Oil marks are probably the most difficult type of staining to remove from York stone.
We recommend Floorseal Cement & Grout Haze Remover for the removal of cement-based products which leave hazing.
Floorseal Cement & Grout Haze Remover can be applied to York stone and general sandstones. Do not apply to fully acid-sensitive surfaces like limestone, marble, travertine, or concretes.
The product is typically applied undiluted but can be diluted for very minor marking.
Hazes and smears of grout, cement, or lime are easy to remove. Larger lumps or thicker coatings may need chipping/scraping off before the final haze is removed. Thick coatings of cement may require abrasion. Chemical treatment (regardless of brand/type) is for the removal of hazes, not thicker coatings.
After using this product, rinse away with plenty of clean water and allow the floor to dry.
Test before use!
Be aware some floors described (or thought to be) as natural stone or sandstone flags are acid sensitive. An example of this is the local stone found in the Cotswolds. This natural stone is sometimes described as sandstone when it is in fact Oolitic limestone, so acid-sensitive! Always identify your stone before using an acidic solution.
The removal of efflorescence is usually easy; it can often be carried out with just a brush – if the efflorescence has appeared recently.
Efflorescence is a salt deposited on the surface after moisture has evaporated. It can be removed by brushing/rinsing it away or applying Cement & Grout Haze Remover.
Both brushing/rinsing or treating with a product can be successful at removing a salt. But it can return if the underlying issue is not resolved. This may be because the floor is inherently damp, or it occurs at only certain times of the year. If so, the salting can become a ‘crust’ and is difficult to remove due to calcification unless abraded.
Once the efflorescence is removed check for any re-occurrence. If efflorescence reoccurs it may be linked to a newly laid exterior stone (which is still drying). Or the floor has an ongoing damp issue, typically if the floor is laid on earth.
Please be aware that efflorescence can occur after deep cleaning of any old floor. Particularly old floors where there is no damp-proof membrane present. Generally, it is not serious, the salting can usually be removed by brushing it away or with a treatment of Floorseal Cement & Grout Haze Remover.
Removing rust can be carried out with Floorseal Rust Remover for Stone. It is a non-acidic solution which can be also applied to York sandstone or other acid-sensitive stones.
This product is to be applied undiluted (it turns a purple colour when reacting with rust) and should be rinsed away before it dries. Do not allow the product to dry on the surface.
Floorseal Rust Remover for Stone will remove surface contaminations and ingrained rusting. With heavier rust stains, you may need to apply the solution more than once to remove all staining. Whilst the solution/rust/stone retains a strong colour you should keep re-treating until the marks clear.
The removal of old sealers is problematic and not always economically possible. Solvent-based acrylics are very difficult to remove and will require a solvent-based stripper to be successful.
Polyurethane sealers are very difficult to strip from interior floors. They require a very powerful stripping agent, these stripping agents are not particularly pleasant! They create strong fumes and are generally unpleasant to work with.
In our experience, if polyurethane has been applied to an interior floor, many people prefer to sand/media blast the surface (where possible). This is often carried out on old Yorkshire sandstone slabs as a property is renovated i.e. not occupied.
It is not possible to fully remove impregnating sealers (or required). Cleaning will break surface tension and allow more impregnator to be applied. Over time old impregnators will break down so are usually not much of a problem.
If the stone has a shiny topical sealer applied i.e. one that dries as a film on the surface, they are difficult to remove. The exception to this is wax, but wax is rarely applied to York stone.
To strip a sealer, you will need to identify which sealer it is by brand/type. There is no ‘one’ product that will strip all sealers. If the sealer is unknown, you will need to purchase a few different stripping agents and test them. Stripping floors usually requires a professional familiar with stripping processes to undertake the work.
Screeds and bitumen often lift away from the York sandstone in sheets, so appear to be easy to remove. Unfortunately, we have found that bitumen often penetrates the surface of the stone. This is common on old interior Yorkshire sandstone flags. The traces of bitumen may still be present on exterior York stone flags as the contamination is lodged in the pores. Many reclaimed (interior) stained flags have been used to then make patios – or re-laid within other houses.
Screeds, if cement-based, can cause the surface of the stone to become softer as moisture is held/trapped under the screed. This can also happen if old sandstones have been under laminate (or other floor covering) for a long period of time. Trapped moisture collecting at the juncture between the stone and the screed causes various issues such as delamination, discolouration and dusting.
Old floors appearing from under bitumen and screeds are usually in poor condition. If bitumen has been applied sand/media blasting is often the only solution. If the surface has become soft and is de-laminating the same applies.
It is possible to remove any general cement-based residues with Floorseal Cement & Grout Haze Remover.
To date, we have not found any totally (cost) effective way of using a cleaning agent to remove ingrained bitumen residues, although there are some solvents on the market which have limited impact.
We have also used various brush attachments, fitted to mechanical rotary machines, to test their effectiveness in removing the issues listed above. We have found that they produce mixed results. Mechanical methods tested include diamond pad systems, diamond brush systems & silicon carbide brushes.
If an interior York stone flagged floor is heavily stained with bitumen, or if it has become soft and is de-laminating, then sand/media blasting possibly offers the best solution – it is a last resort though.
Obviously, a grimy or even blackened floor can respond to intensive cleaning with Floorseal Stone Floor Cleaner. Sand/media blasting is a last resort for any interior floor.
Exterior York stone floors can be cleaned with pressure washers, black spot lichen removal can be carried out with Floorseal Black Spot Remover Plus.
When pointing an interior floor, we have pointed with both lime and sand & Portland cement mixes, depending on the situation. On very old floors where there is a narrow, almost non-existent joint, it is time-consuming work.
We have widened some narrow joints to avoid the patchwork quilt effect i.e. some areas obviously pointed and others not. The Victorians followed a floor laying system known as monolithic fixing. In other words, they butted one slab directly up to another. Lime from the ‘bed’ underneath was pushed up from below, due to the weight of the slab.
Over time some joints become wider, and others remain narrow. In this situation, if you repoint without remedial work, you will end up with the patchwork effect. It is for this reason widening the joints to at least 4mm is preferable. When the floor is finally pointed the floor will look more attractive.
If an old floor is being uplifted and re-laid most builders will relay the floor with a 25mm joint and fit a damp proof membrane under the floor. This wider joint means it is possible to identify a stone floor which has been uplifted/disturbed. Or perhaps reclaimed York Stone slabs fitted where previously there were no flagged floors present.
Exterior York stone floors formed from older slabs look prettier with a sand & cement mortar. Many landscapers will opt to use a brush in compound on newly laid ‘modern’ York stone pavers.
Sand & cement mortars are usually stronger than brush in compounds. The resin-based brush in compounds should not be used indoors; they are weaker and usually appear out of character. In our opinion resin-based brush in compounds have a very limited lifespan.
Floorseal Stone Floor Cleaner is used to remove most ingrained dirt/marks and superficial oil marks. This product can also be used to remove water-based paints (with dwell time) and some old water-based acrylic sealers. This product will help break the surface tension created by old impregnating sealers.
Floorseal Cement & Grout Haze Remover use for the removal of cement-based grouts and general cement/mortar staining. The solution can be used to remove the haze from lime pointing & efflorescence salting.
Rust Remover for Stone is a non-acidic rust remover suitable for use on most kinds of stone. It can also remove iron sulphate fertiliser staining.
Black Spot Remover Plus can be used on exterior sandstone to remove black spot lichens. It will also remove other organic contaminations like algae and bird droppings.
Stone Pro for use on interior surfaces such as lintels and stone mullions. Stone Pro will remove black moulds which form quickly during the colder months of the year.
Floorseal Black Spot Remover Plus can be used in conjunction with Floorseal Cleaner Additive. Cleaner Additive will thicken the product creating a slight foam. It helps to prevent premature drying and makes the removal product cling to vertical surfaces.
Please Click Here to view all our products & accessories for cleaning and sealing York sandstone. This includes our handy ‘how to’ guides & user 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
