How do I clean and maintain decking?

Decking has one significant hazard — it becomes genuinely slippery when algae grows on it — and one common maintenance error, which is pressure washing it hard enough to raise the grain. Raised grain holds more water and more algae, so aggressive cleaning makes the slipperiness worse over time.

Safety

What you'll need

• Stiff brush
• Decking cleaner
• Hose
• Thin tool for clearing gaps
• Decking oil (optional)

Step by step

1. Sweep thoroughly and clear the gaps between boards.Trapped debris holds moisture against the timber, which is what causes rot and feeds algae. A thin blade or a jet of water clears it.
2. Check every board for softness, rot and loose fixings.Press with your heel. A board that gives is rotten and needs replacing before anything else.
3. Wet the deck and apply a decking cleaner, following the dilution on the label.Most contain a biocide that kills algae rather than just removing the visible film.
4. Leave it to dwell, then scrub along the grain with a stiff brush.Along the grain, not across. Cross-grain scrubbing roughens the surface.
5. Rinse thoroughly with a hose.A pressure washer on a wide fan at a distance is acceptable; a close pinpoint jet is not.
6. Let it dry completely — at least two dry days.Oil applied to damp timber won't penetrate and will sit on the surface and go tacky.
7. Test whether it needs oiling by splashing water on it.If it beads, the finish is intact. If it soaks straight in, it needs re-oiling.
8. Apply decking oil along the grain, in thin coats, on a dry overcast day.Direct sun makes it dry before it penetrates. Thin coats, following the product's instructions.

Tips

• Annual cleaning before autumn is the right rhythm — you go into the wet months with a clean surface rather than a slippery one.
• Anti-slip decking strips are worth fitting on steps and any deck that stays shaded, and they're much cheaper than a fall.
• Oil rather than varnish for decking. Varnish forms a film that cracks and peels under foot traffic and weather; oil penetrates and wears gradually.
• Rags soaked in decking oil can self-heat and ignite. Lay them out flat to dry outdoors before disposal, never bundled in a bin.

Common mistakes

• Close-range pressure washing — It raises the timber grain, leaving a rougher surface that holds more water and more algae.
• Oiling damp timber — The oil can't penetrate, sits on the surface and stays tacky.
• Ignoring debris in the gaps — It traps moisture against the boards and is a leading cause of rot.
• Bundling oily rags in a bin — Drying oil generates heat and rags can spontaneously ignite. Lay them flat outdoors first.

Questions people ask