Block paving cleaning and re-sanding explained
Why block paving needs re-sanding after cleaning, and how to keep it looking its best.
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The fastest, most effective way to remove moss and algae from a patio is pressure washing, followed by a treatment to slow regrowth. For lighter growth you can use a stiff brush with a dedicated patio cleaner or a diluted solution, but for established moss, algae and black spots, professional pressure washing restores the surface in a single visit. The key is matching the pressure and method to your specific surface.
Why moss and algae take over
Moss and algae thrive wherever it is damp and shaded, which is why north-facing patios, areas under trees and shaded driveways are usually the worst affected. Beyond looking tired and green, the growth makes paving genuinely slippery and unsafe, especially in wet British weather. The Royal Horticultural Society notes that algae and moss are most active in cool, damp conditions, which describes much of the UK year.
Method 1: pressure washing (most surfaces)
Pressure washing strips moss, algae, dirt and black spots quickly. It works on most hard surfaces, but technique matters:
- Clear the surface and pre-soak stubborn areas.
- Use a fan nozzle, not a pinpoint jet, to avoid gouging.
- Keep the lance moving and at a consistent distance.
- Work in overlapping passes for an even finish.
- Rinse debris away and let the surface dry.
Method 2: brush and treatment (light growth)
For a light green film, a stiff brush with a patio cleaner often does the job without a pressure washer. Apply the cleaner, leave it to work, scrub, then rinse. This is gentler and a good top-up between deeper cleans.
Match the method to your surface
| Surface | Best approach |
|---|---|
| Concrete and stone slabs | Pressure washing |
| Block paving | Pressure washing, then re-sand the joints |
| Natural stone (softer) | Lower pressure and care, or professional cleaning |
| Decking | Lower pressure and the correct nozzle to avoid splintering |
Block paving needs kiln-dried sand brushed back into the joints after washing, or the blocks can shift. This is one of the most common DIY mistakes.
How to stop moss coming back
Cleaning removes what is there now, but regrowth is inevitable in damp spots unless you slow it down. Improving drainage, cutting back overhanging branches to let light in, and applying an algae or moss treatment after cleaning all keep the surface cleaner for longer.
When to call a professional
If the growth is established, the area is large, or you are unsure about pressure on a softer surface, professional driveway and patio cleaning is the safe choice. We use surface-appropriate pressure, re-sand block paving and can treat the area to slow regrowth, across Derby and the surrounding towns.
Need a hand in Derby & Derbyshire?
Get a fast, free, no-obligation quote for driveway & patio from your friendly local eMobile Cleaning team.
