Maintenance
Portland stone is extremely durable and needs very little maintenance.
However, there are steps you can take to help prolong its lifespan.
Below we cover the main areas that clients frequently ask our advice on, should your query not be found please get in contact with our team.
General maintenance
The durability of natural stone can be found in the country’s wealth of historic buildings, many of which are centuries old.
Our limestone requires little maintenance and will naturally weather over time. But certain factors can cause further deterioration.
Be aware, you do not need to clean the stone to prolong its lifespan. The only reason for cleaning is to improve its appearance.
General steps to take:
- Do not leave metals or treat wood touching the stone for long periods
- Avoid spilling oils or organic substances onto the stone
- Do not treat the stone with salt – this will lead to delamination and pitting
- We do not advise painting Portland stone
Stubborn stains require specialist cleaning. Never use patio cleaner or acids to clean the stone.
Larger damage requires replacement of the stone. We advise contacting the supplier of the stone. You will need to ensure the replacement is from a similar bed to ensure it matches the existing stone.
This will only be temporary, but you can clean it using a stiff brush and rinsing with clean water then using an algaecide treatment to control this.
The external application of a proprietary persistent biocidal chemical can help to inhibit future growth of algae and lichen however, expert advice should be sought been applied.
Internal stonework
Internal stonework would normally be maintenance free, although if dust accumulates this may require a light soft brushing and a wash down using clean water and a sponge. An alkaline detergent can be added and a fine abrasive may be used to remove stubborn stains.
Fixtures
Metal fixtures attached to stonework can cause staining due to either run-off or corrosion from the metal itself. For fixing letters or similar light weight objects stainless steel or plastic fixings should be used if required.
Heavier items should only be attached to stonework after a structural appraisal of the fixings required and the ability of the stonework to accept them, care should be taken to ensure any additional loads have been taken into account. It is generally advised that heavy items should never be attached to stone cladding.
Sealant
Care should be taken to make sure that the sealant does not affect the appearance or longevity of the stone.
We do not recommend the use of sealants but in certain situations where this may be necessary (kitchen floor for example), you should consult with the sealant manufacturer for the most suitable application.
Expert guidance should be sought from reputable companies such as Lithofin for advice on sealing natural limestone.
Silicone water repellents are popular as DIY wall coatings, but must be selected carefully to ensure compatibility between the water repellent and the stonework. In old structures they should not be used on decayed or friable masonry or where salts could accumulate behind the surface.
When treating a surface such as cladding the clean appearance may last longer but there are risks involved. By sealing a section of the area or its entirety, differential weathering will occur leading to potential streaks and increased water flow down the face of the wall, this can cause penetration problems at a lower level.
Any water or moisture content trapped within the stone during sealing can cause blow out when exposed to freeze thaw action over a period of time.
Portland Stone Firms will accept no liability for an incorrect sealant used on our products.
External stonework
External stonework will normally require little or no maintenance if used correctly, with the appropriate weather course and exposure to rain.
Periodic inspection should be carried out annually to check for loose pointing and broken water pipes or guttering as this can cause accelerated decay to the stonework.
Most decay in building masonry has water as its origin, and so defective flashing or rainwater disposal should be remedied without delay. Seals in movement joints should also be examined and checked for their continued effectiveness.
Paving
Care should be taken not to apply salt or de-icing chemicals on Portland stone paving as this can lead to salt ingress into the stone, which may then cause spalling to the surface as the salt crystallise.
Brown staining
Brown staining can occur on Portland stone that is fixed onto a concrete backing or when concrete comes into contact with the stone. The stains do not arise as a result of any chemicals inherent in the stone, since there are none. They always form as a result of chemicals being introduced into the stone, either from chemical cleaning fluids or from cementicious materials.
In our experience the only way to avoid this is to use conventional hand set masonry with no concrete backing and fixed onto a granite or alternative impervious plinth.
We do not advise any remedial treatment of the stone surface, which would always be futile until the concrete mix is fully cured. Brown staining of Portland stone is perfectly normal and will persist for some time. The best remedial action is patience. In our experience gained over many years suggests that the problem will resolve itself in five to seven months with no ill effects.
For a more in depth explanation please download our information sheet.