Wet leaves on a shaded front path are a reason to pause before stepping out with a brush. Start from secure footing, with a safe route around the work and a plan for any water you add. Do not walk across suspect paving to test its grip.
Green growth on brick paving, shown as a surface illustration. Photograph: Shutterstock, via RHS; location unknown.
The RHS identifies a thin green coating as typical of algae, while moss forms more substantial tufts. Dampness and shade favour growth. Pale, flat marks may instead be lichens, which can also occur in bright, dry places. The practical priority is a surface people walk on, especially a step or entrance; growth on an ornamental feature need not prompt the same response.
1. Make access safe and clear loose debris
Keep children, pets and visitors away from the working area. If the only entrance is dangerously slick, or there is no stable place to work, arrange help and safe access before cleaning. Work in suitable daylight and weather, with footwear that gives secure footing. Avoid adding water when frost or freezing conditions could turn the route into a different hazard.
From secure ground, remove loose leaves and other debris first. Marshalls recommends regular sweeping and avoiding prolonged contact between wet leaves and paving. Collect the material rather than washing it into a drain. Once the surface is visible, look for loose units, crumbling joints and places where water stands. Those defects affect what cleaning it can tolerate.
2. Check the material before scrubbing
Find the paving supplier’s care instructions, including those for the jointing material or sealant. A method suitable for sound concrete paving may be wrong for weathered brick, soft stone or a coated surface. If you cannot identify a vulnerable material, ask the supplier or a paving specialist before choosing tools or chemicals.
For sound paving where the manufacturer permits it, start with a bristle brush and a small inconspicuous trial. Marshalls describes brushing with a suitable detergent solution followed by a thorough clean-water rinse for general dirt and algae. Use a product compatible with the exact surface, follow its instructions and remove all residue. Do not assume a wire brush is harmless to every stone or finish.
Lift loose moss carefully without gouging sound joints. Stop if the paving surface or jointing starts to break away. Timber and composite decking need their own manufacturer’s method; treating them like stone can damage their surface. A cleaned colour is not proof of safe grip, so keep the route protected while it remains wet and reassess it before reopening.
3. Resist turning up the pressure
Marshalls warns that pressure cleaning can remove jointing material and damage paving. Its guidance varies with the product and joint system, which is a good reason to follow the instructions for yours rather than adopt one pressure or nozzle distance for every path. A powerful jet is a poor way to investigate already failing pointing.
If pressure washing is appropriate, wear eye protection and follow the machine’s safety instructions. Electrical Safety First advises RCD protection for sockets supplying outdoor equipment, checking cables for damage and keeping spray away from electrics. Work from a stable position, never a ladder, and do not use a pressure washer in rain or wind. If those conditions cannot be met, choose another method or get help.
Plan where rinse water and loosened material will go before starting. Keep contaminated runoff away from ponds, watercourses and planted areas; do not assume a surface-water drain is an acceptable disposal route for cleaning chemicals. Avoid improvised bleach or acid mixtures. Product instructions and the paving supplier must govern any chemical treatment, including protection for people, animals and nearby plants.
4. Deal with water that keeps returning
The RHS recommends keeping drains clear of leaves and reducing avoidable shade where practical. It also cautions that growth will return if the conditions remain unchanged. Safe, reachable maintenance may help, but do not tackle overhead branches or alter drainage simply to complete a patio-cleaning job.
After rain, observe the path from firm ground. Repeated pooling, visibly displaced paving or deteriorating joints call for a competent paving or drainage assessment. If you have already noticed movement underfoot, report it rather than stepping on suspect units to test them. Ask whether falls, settlement or a blocked outlet need correcting, and where water can safely discharge. If the puddle is still there once the leaves are gone, make that the next job to investigate before buying a stronger cleaner.