Know what your patio is made of
Most Kent gardens have one of a handful of patio types: riven concrete slabs, Indian sandstone, limestone, slate, or older brick and clay pavers. Each behaves differently. Concrete slabs are hard wearing and forgiving. Sandstone is porous and relatively soft, so it absorbs stains readily and can be etched by high pressure held too close. Slate is dense but can flake along its layers, and limestone can react badly to acidic products.
If you are not sure what you have, a photo is usually enough for us to judge the right approach before we arrive, and it goes into your free written quote.
Why patios go green and black
Patios sit low, often beside lawns and borders, and they stay damp far longer than a driveway because foot traffic is light and planting shades them. Algae forms the green film first, then lichen settles as small black or grey spots that grip hard onto the stone. Moss fills the joints and weeds follow. In practice the north facing end of a patio, and anywhere under a tree, is usually the worst.
How the clean is carried out
A careful patio clean starts with clearing furniture and pots and brushing out loose debris. Joints are raked where weeds have taken hold. The surface is then washed at a pressure chosen for the stone, working in overlapping passes so the finish is even rather than striped. Delicate stone is treated more gently, sometimes with a treatment left to dwell so the growth releases without heavy force.
Once the surface is rinsed, joints can be repointed or refilled where they have eroded. On a sand jointed patio that means brushing new sand back in, while mortar jointed patios may show gaps that need attention separately.
Signs the wrong method was used
These are the marks that give away a rushed or heavy handed patio clean.
- Pale swirls or lance lines across the stone
- Soft sandstone faces that look sandy or pitted afterwards
- Joints blown empty and not refilled
- Muddy slurry left on walls, doors and neighbouring plants
- Black lichen spots still visible once the stone has dried
Lichen spots need patience
Lichen is the most stubborn thing on a patio. The visible spot can be removed, but the root structure sometimes leaves a faint pale mark in the stone that fades over the following weeks as weather does its work. A treatment applied after cleaning helps prevent new spots forming. Blasting harder at lichen rarely helps and is the fastest route to damaged stone.
Keeping it safe and clean afterwards
Sweep the patio regularly, especially in autumn, so leaves do not rot on the surface. Trim back plants that overhang it, and check that water drains away rather than pooling. Some owners seal natural stone once it is clean and dry, which can help with staining from food and drink spills. The 9 photo patio gallery on our homepage shows a real OOR External patio job from start to finish, so you can see the kind of result to expect.