How to Clean Patio Slabs With or Without a Pressure Washer

Why Patios Need Cleaning

Patios in the Chilterns take a beating. The wet winters, the chalk dust that blows onto surfaces, and the shade from mature trees all encourage algae and moss. A slippery green patio is not just unsightly, it is a safety hazard, especially for elderly relatives and young children. Regular cleaning keeps patios safe and looking good.

The right cleaning method depends on the surface. Hard surfaces like concrete and block paving can take pressure washing. Soft stones like Indian sandstone and limestone need gentler treatment to avoid damage. This guide explains how to clean each type of patio safely.

Step 1: Sweep and Clear

Before any cleaning, sweep the patio thoroughly to remove loose dirt, leaves and debris. Remove all furniture, pots and obstacles. Check the joints for weeds and dig them out. A clean, clear surface is essential for effective cleaning.

Step 2: Treat Stains

Different stains need different treatments:

• Oil stains: apply a dedicated oil remover, brush in, leave for 30 minutes, rinse off.
• Rust stains: apply a rust remover (oxalic acid based), leave for 15 minutes, rinse off.
• Organic stains (leaves, berries): apply a patio cleaner with sodium hypochlorite, leave for 30 minutes, rinse off.
• Barbecue grease: apply a degreaser, brush in, rinse off.
• Bird droppings: scrape off, then wash with soapy water.
• Chewing gum: freeze with a freeze spray, then chip off.

Step 3: Choose Your Cleaning Method

Method A: Pressure Washing (for hard surfaces)

Suitable for: concrete, block paving, brick, flagstones.

1. Hire or buy a pressure washer (110 to 150 bar is enough for most patios).
2. Test a small inconspicuous area first.
3. Work in sections of 2 to 3 square metres.
4. Keep the lance 20 to 30cm from the surface.
5. Keep the lance moving to avoid damaging the surface.
6. For block paving, re-sand the joints with kiln-dried sand after washing.

Method B: Hand Cleaning with a Stiff Brush (for soft stones)

Suitable for: Indian sandstone, limestone, slate, tarmac.

1. Mix a patio cleaner with water according to the instructions.
2. Apply the cleaner to the patio with a watering can.
3. Leave for 15 to 30 minutes (do not let it dry).
4. Scrub with a stiff-bristled brush.
5. Rinse with a hose or bucket of clean water.

This method takes longer than pressure washing but is safer for soft stones.

Method C: Chemical-Only Cleaning (for delicate surfaces)

Suitable for: very old or delicate stone, rendered walls, painted surfaces.

1. Apply a patio cleaner with a sprayer or watering can.
2. Leave for 30 to 60 minutes.
3. Rinse with a hose on low pressure.
4. Repeat if necessary.

Surface-Specific Cleaning Guide

Concrete

Tough surface that can take pressure washing. Use high pressure, but keep the lance moving. Re-sand any joints. Cost: 50 to 100 pounds DIY, 150 to 350 pounds professional.

Block Paving

Pressure wash on medium pressure. Always re-sand the joints with kiln-dried sand after washing. Consider sealing to keep the surface cleaner for longer. Cost: 60 to 120 pounds DIY, 200 to 450 pounds professional.

Indian Sandstone

Soft stone that can be damaged by high pressure. Hand clean with a stiff brush and patio cleaner. If pressure washing, use low pressure (under 100 bar) and keep the lance 30cm away. Cost: 70 to 150 pounds DIY, 250 to 500 pounds professional.

Limestone

Very soft stone. Hand clean only. Use a dedicated limestone cleaner (acid-free). Never use bleach or acid-based cleaners on limestone. Cost: 80 to 150 pounds DIY, 250 to 500 pounds professional.

Timber Decking

Use a dedicated decking cleaner, not pressure washing. Pressure washing raises the grain and damages the timber. Scrub with a stiff brush, rinse with a hose. Cost: 50 to 100 pounds DIY, 150 to 300 pounds professional.

Tarmac

Use low pressure only. High pressure damages tarmac. Better to hand clean with a stiff brush and tarmac cleaner. Cost: 50 to 100 pounds DIY, 150 to 300 pounds professional.

How to Prevent Patio Staining

• Seal the surface: a sealant keeps the surface cleaner for longer. Apply every 2 to 3 years.
• Improve drainage: standing water encourages algae. Fix drainage problems.
• Trim overhanging plants: shade encourages algae. Let more light in.
• Sweep regularly: leaves left on the patio cause staining.
• Treat algae annually: apply an algae killer in autumn to prevent winter growth.

Cost of Patio Cleaning

Common Mistakes

• Using high pressure on soft stone. Indian sandstone and limestone can be permanently damaged. Use low pressure or hand clean.
• Using bleach on limestone. Bleach etches limestone and leaves white marks. Use a dedicated limestone cleaner.
• Not re-sanding block paving. Pressure washing removes the joint sand. Always re-sand with kiln-dried sand.
• Not treating stains first. Pressure washing alone will not remove oil or rust stains. Treat with the right chemical first.
• Cleaning in winter. Frost can damage wet surfaces. Clean in spring or autumn.

Frequently Asked Questions

Can I use bleach to clean my patio?

On concrete and block paving, yes, diluted 1:10 with water. On sandstone and limestone, no. Bleach etches soft stones and leaves white marks. Use a dedicated patio cleaner instead.

Will pressure washing remove weeds from the joints?

It will remove the tops, but not the roots. Dig out weeds with a knife or weed tool first, then pressure wash.

How do I stop my patio going green again?

Improve drainage, trim overhanging plants to let in light, and apply an algae killer in autumn. Sealing the patio also helps.

Get Help Cleaning Your Patio

If you need help cleaning your patio in Oxfordshire, Buckinghamshire, Berkshire or Bedfordshire, send us a WhatsApp with photos and we will aim to respond within 12 to 36 hours, Monday to Sunday.

Further Reading

• When to pressure wash a patio
• Why patios go green and slippery
• Pressure washing cost guide

Sources and citations

This article draws on the following sources. Specific claims are cited inline where relevant.

1. CGM field records (2025-01. Site observations from gardens across Oxfordshire, Buckinghamshire, Berkshire and Bedfordshire.
2. Royal Horticultural Society (2024). RHS Gardening Advice and Plant Finder. Available at rhs.org.uk.
3. Met Office (2024). Regional climate averages, South East England. Available at metoffice.gov.uk.
4. British Geological Survey (2024). Soil parent material data for the Chilterns and Thames Valley. Available at bgs.ac.uk.