The level of weeds, moss, algae etc. determines the level of cleaning required, but generally, block paving would be hot pressure cleaned, old sand in joints removed and then re-sanded with fresh kiln-dried sand. Additional treatments can be advised to ensure the best results possible. Patios, paths and decking are a general hot clean, with decking being cleaned at a lower pressure to avoid damage and the dreaded stripe effect! In certain instances, pre-treatment may have to be used to eradicated any biofilm present.