Material guide
Sandstone restoration and care
Porous, textured, and mostly used outdoors. Cleaning, sealing, and slip resistance matter more than polish.
Sandstone is a sedimentary stone of cemented sand grains, and it is defined by porosity. It absorbs water readily, which makes it prone to biological growth, salt movement, and staining — but also gives it the open, matte character it is chosen for.
Most sandstone we see is external: paving, pool surrounds, cladding, and steps. The work is generally cleaning, treating growth, addressing salt damage, and sealing appropriately, rather than the grind-and-polish sequence used on interior floors.
Sandstone is not usually a candidate for a polished finish. Its structure does not support it, and the look would be wrong for the material.
Behaviour
What makes sandstone different
These properties are the reason the method changes. They are not trivia.
- Highly porous and absorbent
- Prone to biological growth in damp and shaded conditions
- Susceptible to salt attack, especially near pools and coastlines
- Naturally textured, offering good slip resistance when clean
- Softer varieties can erode and shed grains over time
Common problems
What goes wrong, and whether it can be put right
Described as you would notice it, then what is physically happening, then what restoration can realistically achieve.
- 01
Green, black, or grey growth, slippery underfoot
- Cause
- Algae, lichen, and mould thriving in a porous, damp surface.
- Outlook
- Correctable with appropriate treatment. How long results last depends on shade, drainage, and water exposure.
- 02
White crystalline deposit or powdery bloom on the surface
- Cause
- Salt crystallising as moisture moves through and evaporates from the stone — efflorescence. Common where paving sits over damp ground or near pools.
- Outlook
- The deposit can be removed, but it recurs unless the moisture path is addressed. An honest assessment covers where the water is coming from, not just the surface.
- 03
Surface crumbling, spalling, or shedding sand
- Cause
- Salt crystallising within the stone rather than on it, or freeze-thaw and weathering in softer varieties.
- Outlook
- This is deterioration, not soiling. Some is stabilisable; badly spalled stone may need replacement. Not something to promise on before seeing it.
- 04
Dark oil or rust staining on driveways and paths
- Cause
- Absorbed vehicle fluids or iron from metal furniture and fixings.
- Outlook
- Often substantially improved by poulticing. Rust in particular can be stubborn and may not fully clear.
Looking after it
Day-to-day care for sandstone
A good share of the damage we repair was avoidable. This is the short version of how to avoid it.
Do
- Keep surfaces swept and rinsed before growth takes hold
- Ensure water drains away rather than pooling
- Use a breathable sealer suited to external stone
- Deal with rust-causing fixings and furniture feet
Avoid
- High-pressure washing, which erodes the surface and drives water in
- Film-forming sealers that trap moisture and then blister
- Acidic cleaners on adjacent calcite stone or grout
Finishes
Finishes achievable on this stone
The finish is chosen to suit the stone and the room it is in, not applied as a default.
- natural
- textured
- honed
Other materials
We restore more than one kind of stone
Looking for a particular job rather than a particular stone? Browse stone restoration by what needs doing.
Not sure what your sandstone needs?
With external sandstone the important question is usually where moisture is coming from. Treating the surface without addressing that produces a result that does not last, so the assessment looks at both.