Why Your Patio Needs More Than a Hose-Down

British weather is hard on paving. Between the damp winters, the shaded corners that never quite dry out, and the odd heatwave, your patio quietly collects a layer of algae, lichen, moss and general grime. It starts as a faint green tinge in the joints, then spreads across the surface until the whole area looks tired and feels slippery underfoot.

A quick blast with the hose might shift the worst of the mud, but it does nothing about the algae holding on beneath. And once paving is clean, leaving it bare means it will soak up every spill, leaf stain and splash of oil that comes its way. The answer is a two-part job: clean it properly, then seal it with a breathable product so it stays cleaner for longer.

Choosing the Right Cleaner

Not all patio cleaners are equal, so match the product to the problem.

• Light green algae and general dirt: a general-purpose patio cleaner, diluted to the maker's instructions and applied with a watering can or low-pressure sprayer.
• Black spot lichen and stubborn staining: a dedicated fungicidal wash. These need more dwell time and often a second application.
• Oil, grease and barbecue splatter: a degreaser or a poultice, applied before you clean the rest of the patio.

Always work in sections of a few square metres rather than soaking the entire patio at once, and keep the cleaner off lawns, borders and neighbouring walls. If you have plants nearby, water them thoroughly before and after to dilute any run-off.

Cleaning Step by Step

Start by clearing the area — furniture, planters, that rogue bag of compost — then sweep off leaves and loose debris. Wet the paving first so the cleaner doesn't dry out too quickly, then apply your chosen product at the recommended dilution and leave it to work for the time stated on the label. Usually that's ten to twenty minutes, but in warm weather check it doesn't dry on the surface.

Agitate the joints and textured areas with a stiff broom, then rinse thoroughly. A pressure washer is fine on most paving, but keep it sensible:

• Use a fan jet rather than a pencil jet, which can etch the surface.
• Keep the nozzle at least 20–30cm from the paving and work at a shallow angle.
• Stay below about 100 bar and avoid lingering on pointing, which erodes quickly.
• Never use a pressure washer on old lime mortar or on soft sandstone — a garden hose and brush is safer.

Rinse again with clean water, then repeat on any patches that still show colour. Algae often needs a second pass, and black spot may need two or three over a couple of weeks.

Let It Dry and Put Things Right

Sealer will not bond to a damp surface, so this stage matters as much as the cleaning. Give the patio at least 24 to 48 hours of dry weather to dry out completely. Check the joints too — if pointing has crumbled, rake out the loose material and repoint before sealing, otherwise water will find its way underneath.

While you're inspecting, note any wobbly slabs or cracked units. Fixing them now saves you sealing over a problem. Once the paving is dry and sound, sweep it once more to remove dust and grit. A dry patio should look noticeably lighter in colour than a damp one; if it still looks dark, give it another day.

Applying a Breathable Sealer

Sealers come in two broad types. Film-forming acrylics sit on the surface and can look glossy, but they trap moisture and tend to peel in frost. Impregnating or breathable sealers sink into the paving and line the pores, repelling water and stains while still letting the stone breathe. For most UK patios, breathable is the better choice.

Pick a dry day with temperatures above about 10°C and no rain forecast for 24 hours. Always test a small, inconspicuous area first to check the finish and colour change.

• Stir the sealer thoroughly — don't shake it, which creates bubbles.
• Apply with a low-pressure sprayer, roller or wide brush, working in manageable sections.
• Go for thin, even coats rather than one heavy soaking. Two coats are typical.
• Allow the first coat to become touch-dry, usually 1–4 hours depending on the product, before applying the second.
• Keep foot traffic off for at least 24 hours and furniture off for 48–72 hours.

Coverage varies by paving type, but most products do roughly 4–6 square metres per litre per coat. Porcelain and dense natural stone absorb less and may need only one coat; porous sandstone and concrete blocks may drink in more.

Keeping It Looking Good

Once sealed, maintenance becomes far easier. Sweep regularly, wash with warm soapy water and a soft brush, and deal with spills quickly before they have a chance to set. Re-sealing is usually needed every two to five years, or when you notice water no longer beading on the surface — a simple test is to flick a little water across the paving and watch whether it sits or soaks in.

Set aside a dry weekend each spring for the annual clean, and your patio will stay safe underfoot, free of green tinges and ready for the first barbecue of the year.