Cleaning and sealing
Indian sandstone.
Sandstone is porous, which is exactly why it looks so good and exactly why it needs a bit of looking after. Here's the routine that keeps it right.
Sweep it through the year, give it one proper wash each spring with a pH neutral cleaner, treat black spot separately, and re-seal every three to five years. That is the whole job.
Start dry
Clear leaves, moss and grit off the surface with a stiff brush before any water goes down. Organic debris left sitting on shaded slabs is what feeds the algae in the first place, and half of what people call staining brushes straight off.
Wash with the right stuff
A pH neutral patio cleaner or a sandstone-specific product, worked in with a brush and left to dwell as the label says. Skip household bleach and anything acidic. Acid eats into the stone and can strip the colour out in patches that never come back.
Jet wash carefully or not at all
If you do use a pressure washer, fan nozzle, moderate pressure, roughly 30cm off the surface, moving in one consistent direction. Too close and you scour the face, blow out the joints, and leave tiger stripes that show up every time it rains.
Treat black spot as its own job
Those stubborn dark dots are lichen with a root in the stone. A dedicated black spot remover, left to dwell and then rinsed, is what clears it. Expect to repeat it on north-facing or heavily shaded patios.
Seal on a dry slab
Wait until the paving is completely dry and the jointing has fully cured, usually a few weeks after laying. Use an impregnating sealer rather than a surface coating, apply thin and even, and pick a dry spell with no rain forecast for 24 hours.
Keep the routine light
A brush through in autumn, a wash in spring, a re-seal every three to five years. Sandstone that gets that looks better at year ten than it did at year one. Sandstone that gets nothing goes green and then people blame the stone.
Can you jet wash Indian sandstone?
Yes, but keep the pressure moderate, use a fan nozzle and hold it around 30cm from the surface. A tight nozzle held close will scour the surface and blow the jointing out. Wash in a consistent direction so the finish stays even.
Does Indian sandstone need sealing?
It is not compulsory, but it is worth it. Sandstone is porous, so an impregnating sealer makes it far easier to clean and slows down algae and staining. Seal once the slabs are fully dry and the jointing has cured, then re-seal every three to five years.
What causes black spots on sandstone paving?
Black spot is lichen, not dirt. Jet washing knocks the top off it but the root stays in the stone and it comes back. A dedicated lichen or black spot remover left to dwell is the only thing that clears it properly.
Why has my sandstone gone white and patchy?
That is usually efflorescence, mineral salts drawn to the surface as the slab dries. It is harmless and it normally weathers off within the first year. If it lingers, a proprietary efflorescence remover will lift it.
Can I use bleach or patio cleaner on sandstone?
Avoid household bleach and anything acid based. Acid attacks the stone and can bleach the colour permanently. Use a pH neutral or sandstone-specific cleaner and always test a hidden slab first.
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