How to Clean Block Paving: The Complete Guide

Why Block Paving Gets Dirty

Block paving is an incredibly durable surface — but it does need regular maintenance to keep it looking its best. The main culprits are algae and green mould (which thrive in the UK's damp climate), weeds growing through joints as kiln-dried sand breaks down, and general traffic staining from oil, tyres and leaf tannins.

The good news is that cleaning block paving is a straightforward job if you follow the right sequence. Done correctly, it will look almost new. Done wrong — particularly with too-high jet wash pressure — you can damage the block surface and blow out jointing sand that takes time to replace.

What You'll Need

• Pressure washer (1,200–1,800 PSI maximum for standard clay or concrete blocks)
• Surface cleaner attachment (strongly recommended over a lance — distributes pressure evenly)
• Stiff-bristled broom or deck scrubber
• Patio and block paving cleaner / algaecide
• Weed killer (sodium chlorate-free formulation — safer for surrounding soil)
• Kiln-dried jointing sand
• Block paving sealer (optional but recommended every 3–5 years)

Step 1 — Clear and Pre-Treat

Before you touch the pressure washer, clear everything off the driveway. Apply a proprietary block paving cleaner or diluted patio algaecide to the entire surface and leave it to work for 15–30 minutes. This loosens biological growth and makes the subsequent wash far more effective — you'll get better results with a shorter wash time.

If weeds are established in the joints, apply a targeted path weed killer a few days before cleaning. This kills the roots rather than just burning off the visible growth, which reduces regrowth.

Step 2 — Pressure Wash Correctly

This is where most people go wrong. The key rules:

• Keep pressure below 1,800 PSI — higher pressures pit the block surface and strip the sand from joints very aggressively
• Use a surface cleaner attachment rather than a lance. A rotating surface cleaner maintains consistent distance, avoids striping, and removes sand much more gently
• Work in the direction of the block pattern — follow the joint lines rather than working across them, which minimises sand removal
• Keep the head moving — don't dwell on one spot

A surface cleaner on a standard domestic pressure washer will clean an average driveway in 1–2 hours and produces dramatically better results than a lance.

Step 3 — Re-Sand the Joints

This step is essential and frequently skipped. Jet washing removes kiln-dried jointing sand from the joints — without replacing it, weeds establish much faster, blocks lose lateral support, and the driveway looks unfinished.

Allow the surface to dry fully (ideally 24–48 hours in dry weather). Then brush kiln-dried jointing sand across the entire surface with a soft broom, working it into all joints. Repeat two or three times until joints are fully filled and no more sand is being absorbed. Blow or brush off any excess from block surfaces.

Use proper kiln-dried jointing sand, not builder's sand or sharp sand. Builder's sand is too coarse and retains moisture, encouraging weed growth.

Step 4 — Apply Sealer (Optional)

Sealing block paving every 3–5 years offers several benefits: it locks the jointing sand in place (significantly reducing weed growth), enhances colour (either a natural matt finish or a wet-look gloss), and makes the surface easier to keep clean in future.

Apply sealer only to a fully dry, freshly cleaned surface. Use a block paving-specific sealer — not a general stone sealer — and follow the manufacturer's dilution and coverage rates. Most sealers are applied with a garden sprayer or roller and need two coats with a drying interval between them.

How Often Should You Clean Block Paving?

A full clean (wash, re-sand, optional seal) every 2–3 years keeps most driveways in excellent condition. In shaded areas with heavy algae growth, an annual wash may be needed. A quick brush with weed killer in spring and autumn takes 10 minutes and prevents joint weeds from establishing between full cleans.

When to Call a Professional

If your block paving has significant oil or fuel staining, multiple sunken or rocking sections, or joints that are entirely void of sand, a DIY clean may not be enough. Oil staining in particular requires specialist degreasers applied before washing, and sunken blocks need lifting, re-compacting the sub-base, and re-laying — which is a job for an experienced installer.

We carry out block paving repairs and re-sanding services across Bristol, Gloucester, Cardiff and the South West. If your driveway needs more than a clean, get in touch for a free assessment.

If you're considering a full replacement rather than a clean, see our guide on 5 signs your driveway needs replacing — and explore the full range of block paving options in Gloucester and across the South West.