8 min read · Updated 29 August 2026
Indian Sandstone Patio Care: A Practical Guide
Why sandstone goes green and orange, what to use on each stain, and the yearly routine that keeps a riven stone terrace looking like it did in year one.
Why sandstone behaves the way it does
Indian sandstone is a porous sedimentary stone. It absorbs water, and that single property explains algae, staining, efflorescence and frost damage. It is not a fault, it is the material, and working with it rather than against it is the whole of good sandstone care.
In our climate a sandstone patio in shade will grow algae. A patio under a lime or a sycamore will stain. Neither means the stone is poor quality.
The yearly routine
Spring: sweep thoroughly, then wash with warm water and a dedicated patio cleaner, working in sections with a stiff brush. Rinse well. Check the pointing for cracks and gaps while it is clean.
Summer: this is the window for sealing if you seal, and for any rejointing. Both need dry stone and settled weather.
Autumn: clear leaves regularly. Leaf litter left on sandstone over winter is the main cause of black tannin staining and the damp mat that algae grows in.
Winter: use sharp sand or grit for ice rather than rock salt, which accelerates efflorescence and can pit the surface.
Stain by stain
Match the treatment to the stain rather than reaching for the pressure washer.
| Problem | Cause | Treatment | Cost |
|---|---|---|---|
| Green algae film | Damp and shade | Algae treatment, soft wash, rinse | £15 - £30 DIY |
| Black spots | Lichen | Lichen specific treatment, repeat | £20 - £40 |
| White powder bloom | Efflorescence from salts | Dry brush, patience, no acid | Free |
| Orange or brown spots | Iron pyrites in the stone | Rust remover for stone, spot treat | £20 - £35 |
| Dark tannin patches | Leaf litter, wet timber furniture | Oxygenated stone cleaner | £20 - £40 |
| Loose or crumbling joints | Failed sand and cement pointing | Rake out and rejoint with resin | £18 - £35 per m² |
Pressure washing without wrecking it
Sandstone is soft enough that a turbo nozzle will visibly erode the surface and leave permanent tramlines. Use a wide fan tip, keep the pressure moderate, hold the lance at least 300mm off the stone and keep it moving in overlapping passes.
Never pressure wash directly into the joints. Even sound pointing will blow out, and once the joints are open, water gets under the slabs and the frost does the rest. If the patio needs that much force to look clean, it needs a chemical clean instead.
Efflorescence: wait it out
The white bloom that appears on new sandstone in the first year is salts from the bedding mortar and the stone itself migrating to the surface as moisture evaporates. It looks alarming and it worries a lot of homeowners.
Do not attack it with acid, which etches the stone and can make it worse. Dry brush it off periodically and it will stop within twelve to eighteen months as the salts deplete. Sealing before that process has finished traps it underneath, which is exactly why we say wait at least six weeks and preferably a full season before sealing new stone.
Sealing and rejointing
A breathable impregnating sealer is worth it on sandstone. It reduces absorption, slows algae and makes spills recoverable. Expect £10 to £16 per square metre applied professionally and reapplication every four to five years.
Rejointing matters more than sealing. Sand and cement pointing on a sandstone patio typically starts cracking at five to eight years. Raking it out and refilling with a two part resin jointing compound at £18 to £35 per square metre stops water getting under the slabs and is the single best thing you can do for the life of the terrace.
We do both, and we will tell you which yours needs. Call 07538 218723 or request a quote through the site.
Frequently asked questions
- How do I clean an Indian sandstone patio?
- Sweep, apply a dedicated patio or algae cleaner, agitate with a stiff brush and rinse. Use a pressure washer only on a wide fan tip at moderate pressure, held well back and never aimed into the joints.
- Why has my sandstone patio gone white?
- That is efflorescence, salts migrating to the surface as the patio dries out. It is normal on new stone, clears within 12 to 18 months, and should be dry brushed off rather than treated with acid.
- Should Indian sandstone be sealed?
- It benefits from a breathable impregnating sealer, applied at least six weeks after laying and ideally after the first season. Expect to reapply every four to five years.
- What causes orange stains on sandstone paving?
- Iron pyrites naturally present in the stone oxidising at the surface. Spot treat with a rust remover formulated for natural stone. It is a characteristic of the material, not a laying fault.