How to Clean Sandstone Patio – Safe Methods That Won’t Damage Stone

Sandstone patios look stunning — but they’re also one of the easiest surfaces to damage if you clean them the wrong way. Many homeowners worry about fading colour, rough patches, or permanent marks after cleaning, especially on premium stone like Indian sandstone. In this guide, you’ll learn exactly how to clean sandstone safely, which methods to avoid, and how to deal with common problems without ruining the surface. Whether your patio is lightly dirty or covered in algae and black spots, this article explains the safest way to restore it without causing damage.

---

Why Sandstone Needs Different Care

Sandstone isn’t like concrete or porcelain. It’s a porous natural stone, which means it absorbs water, cleaning chemicals and contaminants easily. What you put on sandstone doesn’t just sit on the surface — it gets drawn inside. That’s why the wrong products can cause patchy discolouration, white residues, or long-term stains.

Sandstone is also physically softer than stones like granite or slate. Aggressive scrubbing, wire brushes and powerful pressure washing can erode the top layer, leaving the surface rough, faded and more vulnerable to water damage. Once that protective surface layer is lost, the stone weathers much faster.

Another important factor is acid sensitivity. Many types of sandstone contain minerals that react badly with acidic cleaners. This can lead to bleaching, rough patches, or loss of colour. Varieties such as Raj Green, Autumn Brown and Kandla Grey are particularly prone to visible surface damage from acid-based products.

Because of this, sandstone needs gentle treatment, correct products, and low-impact techniques. Never treat it like patio slabs or block paving. Always test first, avoid acids, and use the lightest method that will achieve the result.

---

Safe Cleaning Methods for Sandstone

The key to keeping sandstone in good condition is choosing the least aggressive method that gets the job done.

1. Warm soapy water (best for routine cleaning)
This is the safest option for regular maintenance. Use warm water, washing-up liquid and a soft or medium brush. Scrub gently in sections, rinse thoroughly and avoid letting soapy water dry on the surface. Work with the natural grain of the stone rather than across it.

2. pH-neutral patio cleaner (recommended for deeper cleaning)
For algae, grime and general discolouration, use a pH neutral patio cleaner designed for natural stone. These products clean effectively without damaging the stone or reacting with minerals. Apply evenly using a garden sprayer and follow the dwell time instructions carefully. This is the safest way to deal with biological growth on sandstone.

3. Low-pressure washing (only if absolutely necessary)
If you use a pressure washer at all, it must be on the lowest setting, with a wide fan nozzle and held at least 40–50 cm from the surface. Never use a turbo nozzle. Keep the lance moving and avoid concentrating on joints or edges.

4. Methods to avoid completely

• Acid-based cleaners

• High-pressure washing

• Wire brushes

• Undiluted bleach

• Brick or patio acid

• Grinding or abrasive pads

Always test on a hidden section first before applying anything across the patio.

Patio Guard is pH-neutral and safe for all sandstone varieties. Learn more.

---

Dealing with Common Sandstone Problems

Black spots on sandstone
These are lichen, not dirt. Scrubbing rarely works. Use a spray-and-leave cleaner that penetrates and kills growth at the root. Results are gradual and appear over weeks.

Green algae on sandstone
Warm soapy water can help for light growth, but a pH-neutral cleaner is more effective and prevents quick regrowth.

Oil stains
Absorb fresh spills with paper towel or cat litter. For older stains, use a sandstone-safe degreaser and avoid scrubbing aggressively.

Efflorescence (white marks)
These are mineral salts, not growth. Often they disappear naturally as the stone weathers. If needed, use a specialist remover that is safe for sandstone and never an acid wash.