Sealing Stone Outside

Limestone, Sandstone, Travertine, Marble, Slate, Granite, concrete:
Regardless of what type of flooring you choose, the likelihood is it will require some form of sealing.

This is because natural stone is porous, and therefore if left unsealed, any moisture will be soaked up by the stone making it very difficult to remove, and potentially leaving the surface permanently stained (sometimes even fallen leaves can cause stains).

The best way to prevent all this is to seal the stone.

When you seal a stone, you are essentially filling any voids or pores of the stone with the sealer. This prevents any further liquid to absorb in to the tile, as demonstrated here with this close up shot of a water droplet on a tile sealed with LTP Mattstone.

When sealing natural stone outside it is important to use a breathable impregnating sealer, this will allow the transition of moisture from underneath.
Examples include LTP Mattstone H20 which will leave the stone looking as it does naturally. And LTP External Stone Sealer which will enhance any natural colour in the stone, both of these are water based breathable sealers and will require 24 hours to cure.

It is important to note that all stones located outdoors are susceptible to a condition known as efflorescence.
This blooming is caused by water moving through the substrate of a material and carrying minerals and salts found in the mortar bed, grout, soil or the stone itself.
We have a blog here all about efflorescence.

Its also very important when laying Natural stone to make sure that its fixed on a full bed of adhesive and not spot fixed.
The end result could look like this if its spot fixed.
Spot fixing issue Sandstone

If this has already happened to your patio, we have a blog here.

When sealing different natural stones, what will vary the most will be how many coats the stone will need before it is fully sealed.
Each stone exhibits different levels of porosity. A tumbled Limestone may have a higher porosity level than a Honed and filled Limestone.

Sealing natural stone with Mattstone H20 

Shake bottle before use.

Test the porosity of your stone with water and a teaspoon, using the LTP porosity test.

Once surfaces are clean and dry, apply the product to the surface evenly using a sealant applicator pad, brush or soft cloth.

When sealing its important not to over apply the sealer and redistribute excess, avoid letting the sealer pool on the surface, as this can cause white marks to appear on the stone when it dries.
On highly absorbent surfaces apply several coats wet-in-wet.
After 15 minutes, remove any excess sealer with an absorbent cloth. Do not allow residues to dry on the surface.
Do not walk on the surface for 3 hours and protect from wet conditions for 3 days.

Sealing Stone With LTP External Stone Sealer.

Shake bottle well before use. Apply evenly to the surface using a foam roller or paint brush. On more absorbent surfaces apply further coats at hourly intervals until the surface is completely saturated. Remove any residual sealer if still visible after one hour

Cleaning Tiles Outside

Before you start sealing your stone it is important to make sure your stone is clean and dry, other wise you will just seal in dirt and grime.

Old layers of sealer, dirt residues and light deposits of organic matter and algae must be removed from the surface and pores of the stone.

This can be done by either using LTP Grimex which is a intensive cleaner or LTP Mouldex Paving Cleaner.

To Clean with LTP Grimex, dilute 1:3 with water, apply to the surface with a sponge or water brush and leave to sit on the surface of the tiles for as long as it takes for the dirt to release. (5-30 minutes depending upon the level of dirt). If areas look as if they are drying out just add a little more solution to keep the area wet.

Agitate the surface with a stiff deck brush after approx 10 minutes (scrubber machines can be used).

Continue to scrub while adding clean water. Remove residues from the surface with water or scrubber machine.

Rinse thoroughly with clean fresh water to remove all remaining residues. Use a power washer if necessary.

Allow the surface at least 24 hours to dry before sealing.

To clean with LTP Mouldex Paving Cleaner, Shake well before use.
Surfaces to be treated should be completely dry before application.
Pour solution undiluted directly onto the pavers and spread out evenly using a sponge or paint brush, Garden sprayers can also be used and leave for a minimum of 1 hour.

Apply a little water and agitate with a stiff Deck brush or emulsifying pad to release the dirt and grime, and then rinse thoroughly using a hose or jet wash.
Some stubborn stains and black spot may require a longer treatment, in which case apply and leave on surfaces overnight. If some black spot remains after treatment, It should fade and disappear after a few days following the treatment. If not: re-apply. Keep pets off at all times during treatment. In case of contact with metals, fabrics and painted surfaces rinse with water immediately. Do not use on warm surfaces. Do not apply if rain is imminent. Avoid contact with ponds & plant life: if contact is made rinse well with plenty of water.

General Maintenance.
Weekly or daily depending on conditions, use a hose and a brush to remove any debris that may be lying on the stone.
Then annually if required use LTP Grimex, this will remove surface dirt and grime, possibly every 6-12 months depending on condition.
Dilute Grimex 1:3 parts water and apply the solution on to the surface and agitate.
Leave for 10 minutes before agitating again and then rinse with water.
Allow 24 hours to dry and then if necessary re-apply a light coat of sealer.

PLEASE NOTE: Always follow the detailed instructions on the product labels. Protect stone surfaces from contact with acidic substances. Do not use abrasive materials on honed or polished stones. Avoid using normal detergents or strong bleach cleaners on sealed surfaces as they will gradually remove the protective seal.

Please note that this information is offered as general guidance only and without guarantee. Your specific circumstances may need an alternative approach. In case of doubt, any process should be tried out in an inconspicuous area before general application.


Problem Solving Black Limestone

We are often contacted in particular about black limestone, the appearance of stains and mineral deposits is not uncommon and occurs with most types of limestone, however the appearance on black limestone or darker stone is more prevalent. This is why it is possible to notice some marks appearing even before sealing. As a naturally occurring chemical reaction it is often difficult to avoid. So this blog is all about some of the different things that can happen, what you can do to prevent it or what you can do to resolve the issues as best you can.

Mineral Stains

Mineral deposit stains on black limstone

Mineral stains are sometimes caused when rain water trickles through sand-cement mortar screeds, toppings and bedding under limestone paving can become moderately alkaline. As this rainwater evaporates, its alkalinity increases until the solution becomes saturated.
This solution then can travel to the surface within the limestone where it starts to deposit solids such as white and grey encrustations of calcium carbonate also known as lime plumes.
To remove the the mineral salts from the surface wash the surface with a mild solution of acid*. This will help disperse the mineral salt deposits from the surface.
LTP Grout Stain Remover is a product suitable for the task, dilute 1 part LTP Grout Stain remover in 4 parts warm water and apply to the surface of the stone. Agitate using an emulsifying pad or similar abrasive pad and then rinse thoroughly with plenty of clean water. Repeat process if necessary.
For more information about LTP Grout Stain Remover please see the Technical Data Sheet.

*N.B Grout stain remover may etch the surface and cause the stone to dry lighter.
If the Limestone is either Honed or Polished do not use LTP Grout Stain Remover and instead use LTP Powerstripper.

Mineral deposits causing a banding effect

Halo Stains & Bands Of Mineral Deposits.

This is caused by trace amounts of sodium and potassium oxides within the Limestone which can also be activated by rain water. Even where rain is slightly acidic, the solutions of these salts in rainwater will gradually become alkaline. Surface wetting and evaporation can produce recurrent patches and bands of dampness known as accumulation zones ( rainwater pooling on the surface where it cannot run off).

Evaporation concentrates the alkaline solutions until they become saturated at the  outer limits or edge of accumulation zones. Further evaporation then causes precipitation, crystallisation and immobilisation of the salt at the surface and in pores immediately below the surface. The resulting bands of distinct pigmentation are halo stains as seen in the image above of Limestone.

Grout & Adhesive Stains.


Adhesive Stains On Limestone

Grout and adhesive stains like this appear often, if the stone has been sealed beforehand then the process of removing the residues is easier.
After grouting most of the residues should be taken off with water before it fully dries on the surface. For the removal of most grout residues on Limestone we would recommend using LTP Powerstripper. However on more severe cases as shown in the picture above, using a mild solution of LTP Grout Stain Remover may be more effective.
Grout Stain Remover is an acid based cleaner and will etch any acid sensitive surfaces (Limestone, marble, some sandstones, chrome etc).
We would always recommend to test on a small inconspicuous area first.
LTP Grout Stain Remover Tech Data Sheet.

General Dirt & Grime

If your limestone has been outside for a couple of years, it may have seen better days.
General dirt and grime can be easily removed with LTP Grimex.
Dilute in a bucket of water as per instructions on the back of the bottle, then apply and leave for 10 minutes. Give it a scrub with a deck brush or an emulsifying pad and then rinse with plenty of clean water.
After cleaning allow to dry for 24 hours and then the stone will be ready for resealing.

Protect your Limestone with the correct sealing product.

Sealers used to enhance the appearance and help prevent limestone pavers staining from organic matter outside need to be breathable. LTP Mattstone H20 & LTP Stone Oil are examples of breathable sealers suitable for external use. As well as protecting the stone from staining, breathable sealers will allow the microscopic transition of moisture assisting any trapped moisture to escape through the stone from the mortar and sub surfaces. However, moisture permeating through the stone and sealer to the surface can still dry to leave a calciferous deposit.

Once the stone is thoroughly dry and mineral salt deposits are greatly reduced, general dirt and grime has been cleaned off, reseal the stone with an appropriate limestone sealer. LTP Mattstone H20 is highly effective natural stone sealing solution and is suitable for exterior use. However many of our customers have used LTP Stone Oil after acid washing their stone as it helps to re-enhance and deepen the colour.

Apply LTP Stone Oil to the surface of the stone using a paint brush. Allow it to absorb into the stone and then remove any visible excess from the surface after 45 minutes using an absorbent dry towel. The aim is to completely saturate the stone with as many coats of the sealer as necessary, but do not allow the sealer to dry and leave a film on the surface. Do not apply in direct sunlight.
For more information on how to apply please see the Technical Data Sheet.

LTP Mattstone H20 is applied to the surface with a paint brush, allow to absorb for 15 minutes and then apply a second coat. Remove any visible excess on the surface after 45 minutes.
For more information on how to apply please see the Technical Data Sheet.


Please note that this information is offered as general guidance only and without guarantee. Your specific circumstances may need an alternative approach. In case of doubt, any process should be tried out in an inconspicous area before general application. 

Encaustic Tiles

Encaustic tile

Encaustic tiles are made of two or more colours of clay that are then mixed or inlaid together to create a pattern, they are then fired.
Encaustic effect Cement tiles are created by pouring different colour mineral pigments into a mold, grey cement then fills the rest of the body of the tile, this gets hydraulically compressed and left to set or cure for 3 weeks.
Both tiles are unglazed and would require sealing.
For more information please follow this link.

Prior to sealing it is always advisable to clean the tiles thoroughly with a solution of LTP Grimex. This advice goes for both newly laid and renovation projects. Remember not to use acid based cleaner with encaustic tiles .

When it comes to sealing there are various options available depending on the desired look of the floor, however the most popular are the natural Matt finish using either LTP Mattstone or the water based equivalent LTP Mattstone H20. Depending on the type of encaustic tile being used, up to three or four light coats of sealer might be required. Always test on an inconspicuous area first and buff off any excess.

LTP Colour Intensifier is also popular as its use offers a delicate enhancement of the different coloured patterns within the encaustic tile.

Finally, as always, the use of a compatible aftercare product in this case LTP Waxwash, will ensure optimum longevity for the sealed surface as standard household Encaustic 2 pg guidescleaners may compromise the effectiveness of the seal over time.

Correctly sealed and maintained an encaustic floor should last three to four years before re sealing is required.

To download an information sheet, Please follow the link below.

Encaustic Tiles guide


This information is offered without guarantee . The material should be used so as to take into account of the local conditions and the surfaces to be treated. In case of doubt, the products should be tried out in an inconspicuous area before general application.

Natural Stone – Pedestrian Walkways & Driveways

LTP_Sealing_Cobblestone_ Walkways_and_Driveways_18


LTP Mattstone H20 is both hydrophobic and oleophobic and offers excellent resistance to staining and moisture ingress. If sprayed onto the surface a single coat is normally sufficient, if brushed two coats. The low viscosity allows the active ingredients to absorb into the surface and dry, to provide an in depth mesh of protection within the pores of the stone without creating a film or altering the surface character. Despite being extremely repellent the treated surfaces remain breathable. Dirt and moisture are prevented from absorbing making removal much easier. Ensure that the natural stones are dry and free from as much dust and dirt as possible before treating.

SEALING:        LTP MATTSTONE H20 (environmentally friendly)       5ltr containers

Fill sprayer with 5 litres of LTP Mattstone H20, set pressure to 1 bar. Hold nozzle of the sprayer approximately 50cm from the surface to be treated and apply evenly using a LTP-MattstoneH20_5L_Websweeping motion.
SPRAYERThe sealer will take about 15-20 minutes to absorb into the stone. Gloves, eye protection and face mask should be worn. Two hours after application test a small area for resistance to moisture by flicking a little water onto the surface.
If water beads, enough sealer has been applied. If moisture absorbs, a second coat may be need to be applied. Treated surfaces will take about 3 days to become fully resistant. If Spraying equipment is not available apply using a roller or large paint brush, making sure to work the sealer into any uneven edges of the stone.
Approx coverage: 5ltrs = 50M2


AFTERCARE:    LTP POWER STRIPPER (water based solvent free) 5ltr containersLTP-Powerstrip5L_2011_Web

PERIODICALLY/WHEN REQUIRED spray and scrub surfaces clean. Scrubber dryer

machines can be used in conjunction with LTP Power stripper. Dilution should be 1 part Power stripper with 20 Parts water. This cleaner will help assist removal of general dirt and grime, chewing gum and stains from pollution from the treated external stone surfaces. Approx coverage: 5 ltrs : 500M2



Provided the surfaces are correctly sealed, protection should last 3-4 years before considering applying a top up coat.
After intensive cleaning to remove graffiti or other staining, and once dry, always test for moisture ingress. If evident, cleaned areas should be re-sealed.
When using Mattstone H20, gloves, eye protection and if spraying a face mask with appropriate filter should be worn.
This information is offered without guarantee . The material should be used so as to take into account of the local conditions and the surfaces to be treated. In case of doubt, the products should be tried out in an inconspicuous area before general application.