Sandstone-Fixing & Sealing Outside.

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We have recently been contacted by numerous customers who have been having problems with spot stains appearing on their sandstone patios.

Sandstone Flags with Spot Fixing Issues.

Sandstone Flags with Spot Fixing Issues.

This is a common problem, so we thought we should share why and how this issue sometimes occurs. The pictures in this post are supplied by customers showing the problems that are occurring.

 

Understanding Sandstone

Many of the imported sandstones, and some limestones and granites,are very porous. If fixing natural sandstone or limestone outside DO NOT SPOT FIX!!

They are not man made concrete pavers and should not be treated the same.

The sandstone should be fixed to an even mortar bed and then each piece of stone back buttered for a solid fix…

This will help illuminate possibilities of staining from moisture and mortar.

Natural stones like sandstone are not as dense as concrete pavers and are full of microscopic capillaries. These capillaries can draw up moisture from mortar through to the face of the stone. The moisture dries out to leave a deposit of mortar residue and minerals within the pores of the stone.Img3701 Sealing too soon after spot fixing can sometimes highlight these issues and also slow down the transition of moisture, suspending the cement residues within the stone.

The introduction of moisture from rain can also further highlight these issues. This is because the moisture collects and dwells within the voids between the mortar spots underneath the stone. As it dries out and the moisture rises carrying more minerals from the sand and cement to the surface of the stone.

Most sealers used for outside use are breathable and allow microscopic transition of moisture, so any trapped moisture is still able to dry out should it become trapped beneath the stone. Sealing does not cause the issues associated with spot fixing nor should it be considered a method for covering up the stains should they occur.

If your stone pavers have been spot fixed, then we would suggest not sealing them for at least 3 months after installation. This should allow for any mortars to full harden and any released minerals to completely dissipate. Clean surfaces well using LTP Power Stripper and leave to dry for 24 hrs. Test the sealer on a small area before general application to make sure that the mortar spots are not highlighted and after a few days make the test area wet and allow it to dry out. If staining does not occur the rest of the surface can be sealed.

If your stone has been fixed correctly into a solid bed then we would suggest a drying time of two weeks before sealing. This should allow enough time for all mortars to fully dry. Solid fixing will not allow any rain water to sit beneath the pavers and dwell. Clean surfaces well using LTP Power Stripper and leave to dry for 24 hrs. Seal using an impregnating sealer and apply as many coats as necessary to completely saturate the stone.

When sealing using an impregnating sealer it is important to remember that the solution needs to fully absorb into the stone without drying on the surface and do not apply in direct sunlight. If sealer is still visible on the surface after 45 minutes saturation has been achieved and any excess should be toweled off. For best results allow at least 3 full dry days after treatment.

 

LTP IMPREGNATING SEALERS SUITABLE FOR EXTERNAL USE

LTP MATTSTONE H20

LTP EXTERNAL STONE SEALER

LTP STONE OIL

 

CLEANING SANDSTONES & LIMESTONE  WITH SPOT FIXING ISSUES

Use: LTP Power Stripper

Apply undiluted to the surface of the stone and agitate using a black emulsifying pad. Add a little water and agitate again. Leave the solution on the surface of the stone for 15 minutes and agitate again. Rinse well with water. Repeat until the stains are no longer visible. Leave to dry for a minimum of 24 hours before sealing. Before re-sealing the whole area test the sealer on a small area before general application to make sure that the mortar spots are not highlighted. Leave to dry and after a few days make the test area wet and allow it to dry out. If staining does not occur then the rest of the surface can be sealed.

CLEANING MORTAR STAINS FROM SANDSTONES AFTER POINTING

Use: LTP Grout Stain RemoverGrout_Residue_Remover_Pack2

Apply un-diluted onto the surface of the stone and agitate immediately using a black emulsifying pad to release the mortar stains from the surface of the stone. Using a sponge and water rinse well immediately after use and change rinsing water after every 5 sq/m.

MOULD, MILDEW AND BLACK SPOT

Use: LTP Mouldex

Spray LTP  Mouldex onto the surface of the stone and leave for 1 hour. Using a black emulsifying pad agitate the surface and rinse well with plenty of water. Repeat until all organic matter has been removed. Re-seal surfaces once thoroughly dry.

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

 

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Patio & Driveway Surfaces – Cleaning, Sealing & Maintenance

Natural Stone Surfaces – External Application

Cleaning, Sealing and Maintaining Natural Stone – Part Three

Natural stone has been used as an external surface covering for paths, driveways, patios, court yards, terraces, porch areas,verandas, loggia and sun decks for centuries. As with all natural materials, it does need a certain level of care.

This is the third in a 16 part series of posts that will offer a comprehensive guide to cleaning, sealing and maintaining all types of stone, porcelain, quarry, terracotta and glazed ceramic tiles and surfaces. This post explains the LTP three-step approach to cleaning, protecting and maintaining natural stone surfaces used in external applications such as paths, driveways, patios, court yards, terraces, porch areas,verandas, loggia and sun decks. Natural riven or rough cut stones are often used outside because they are naturally slip resistant. Normally thicker than internally fixed stone they are more robust and harder wearing. The following guide will explain the process and help keep your surfaces maintained and in good condition for many years.

Natural Stone Surfaces – External Application

The following instructions are for sawn and honed, riven or rough cut finish: sandstone, slate, granite, quartzite and rough cut and riven limestone.

Step one: Initial cleaning

Before sealing, clean natural stone thoroughly to make sure that the surface is sealed  effectively. This is true of newly installed surfaces, as well as existing, due to the contamination that can occur during fitting. On existing surfaces such as patios, driveways, paths and terraces remove old layers of sealer, dirt residues and light deposits of organic matter and algae  from the surface and pores of the stone. For newly installed surfaces cleaning should remove all grout and cement residue and any general dirt or grime that has built up while fitting. Bucket, mop, sponge, scrubbing-brush or scrubber dryer machine if available.

Newly installed surfaces

Before grouting and once surfaces are clean and dry: Apply one coat of LTP Colour Intensifier & Stainblock before grouting. This treatment will help with the removal of residual cement and grout from the surface of the stone paths, driveways, patios, court yards, terraces, porch areas, verandas, loggia and sun decksLTP recommends using LTP Grout Stain Remover to clean and remove residual grout and mortar from the textured riven surface of natural stone driveways, patios, court yards, paths, stone terraces,verandas, porch areas and sun decks once they have been laid.

Please note: Do not use LTP Grout Stain Remover on honed and smooth limestone. 
This product is only suitable for use on riven limestone.

Cleaning newly installed reclaimed flagstones, rough cut, honed and tumbled stone surfaces

  1. Dilute LTP Grout Stain Remover 1:2 with water. On rough cut limestone dilute 1:6
  2. Apply solution to the surface with a stiff brush and agitate immediately.
  3. Leave for 5 minutes and agitate again. Rinse well with water.
  4. Rinse well with plenty of clean water.
  5. Allow the surface to dry.

Step One Cleaning External Stone Surfaces

Refurbishing used and heavily soiled stone surfaces

  1. Before sealing the clean stone thoroughly. 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.
  2. Dilute LTP Grimex 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.
  3. Agitate the surface with a stiff deck brush every 5-10 minutes (scrubber machines can be used).
  4. Continue to scrub while adding clean water. Remove residues from the surface with water or scrubber machine.
  5. Rinse thoroughly with clean fresh water to remove all remaining residues. Use a power washer if necessary.
  6. Allow the surface a minimum of 3 dry and damp free days before applying the protective seal.
  7. For the removal of other types of dirt refer to the table below.
  8. Do not allow the sealer to dry on the surface. Carefully buff with a soft cloth or machine to remove any excess. Complete this within 1 hour of application.

For the removal of other types of dirt refer to the list below. If you are unsure please call our helpline for advice.

Step two: Protect your natural stone surface from stains

To protects sawn and honed, riven or rough cut finish: sandstone, slate, granite, quartzite and rough cut and riven limestone surfaces and help prevent staining LTP recommends the application of LTP Colour Intensifier & Stainblock.

The equipment you will need for this task: bucket, applicator, brush, cloth.

Application of LTP Colour Intensifier Stainblock: Enhanced natural finish protects against water, oil, grease, dirt, grime, organic matter and aids maintenance

  1. Clean surfaces and ensure they are dry.
  2. Apply the product to the surface evenly using a sponge, brush or soft cloth.
  3. Redistribute to remove excess product and avoid pooling on the surface.
  4. Allow to dry. Do not walk on the surface for at least 3 hours.
  5. Protect from damp and wet conditions for at least 3 days.

Step 2: Sealing external stone surfaces

Step three: Maintaining your reclaimed flagstones, rough cut, honed and tumbled stone surfaces

Using the correct maintenance product will increase the life of your stone seal, provide more protection against staining and make sure your path, driveway, patio, court-yard, terrace, porch area, veranda, loggia or sun deck looks great. Common household cleaning products often contain harsh substances that can breakdown sealing products applied to stone. For this reason LTP recommends using LTP Grimex on external surfaces sealed with LTP Colour Intensifier & Stainblock. LTP Grimex will remove surface dirt when required (normally every 3-6 months).

Regular maintenance on sawn and honed, riven or rough cut finish: sandstone, slate, granite, quartzite and rough cut and riven limestone

  1. Dilute LTP Grimex 1:3 with water.
  2. Apply the solution to the surface and agitate.
  3. Leave for 10 minutes before agitating again and then rinse with water.
  4. Leave to dry for 24 hours and then if necessary re-apply a light coat of sealer.
  5. Protect from damp and wet conditions for a minimum of 3 days.

Step 3: Maintaining External Stone Surface.

Should you use a professional floor restoration company?

The application techniques described above are achievable by a competent DIY enthusiast using the products as described. However, natural stone products are often expensive and by nature each stone has its own characteristics. We often find that many of our customers prefer to use the experience and skills of a professional stone restoration and cleaning company to make sure that their project is completed to the highest standard. LTP is pleased to associate with the following companies that specialise in natural stone restoration and cleaning:

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.

At LTP we believe in helping to offer solutions and this is why we offer a no obligation
LTP TECHNICAL HELPLINE
, so please give us a call on +44 (0) 1823 666213 and we will be happy to help you.

Visit www.ltp-online.co.uk to buy from the LTP Range of products or find out more about us.