Guide · DY Exterior Cleaning Ltd
How to clean block paving (the professional method)
Clean block paving by pre-treating algae with a biocide, then using a flat rotary surface cleaner at controlled pressure, never a narrow lance. Re-sand the joints with kiln-dried sand afterwards to lock the surface and slow weed regrowth.
Step 1, Pre-treat
Apply a biocide (sodium hypochlorite or quaternary ammonium based) to areas of heavy moss and black lichen. Let it dwell 15,20 minutes. This kills the organic growth so cleaning lifts it cleanly instead of just smearing it.
Step 2, Use a rotary surface cleaner
A flat rotary head, not a narrow lance, is the key to even results. The rotating jets sweep the whole surface at controlled pressure, lifting dirt without firing jointing sand out or scarring the blocks. Held flat with overlapping passes you get an even finish across the whole drive.
Step 3, Detail the edges
A rotary head can't reach right to walls, kerbs and weed lines. Switch to a hand lance to detail those, keep the lance 15,20cm off the surface to avoid scarring.
Step 4, Re-sand the joints
Cleaning will wash some jointing sand out. Once the drive is dry, brush kiln-dried sand into the joints, this locks the blocks back together, helps shed water, and dramatically slows weed and moss regrowth.
Common mistakes
Using only a narrow lance (zebra stripes). Skipping the pre-treatment (moss grows straight back). Cleaning then sealing immediately (paving must be fully dry first). Sealing without re-sanding (sealer doesn't bind to empty joints).