What this guide covers: How to clean timber and composite decking with a pressure washer — including the correct grain direction for timber, how to check composite manufacturer guidance before starting, and why oiling or treating the surface after the wash is essential.
Decking is one of the most satisfying things to pressure wash — the before and after difference is dramatic. It's also one of the easiest surfaces to get wrong. Too much pressure on timber decking raises the grain and splinters the surface. The wrong technique on composite decking can void the manufacturer's warranty. Algae and moss on decking also creates one of the most slippery surfaces in the garden — a thorough clean before the main outdoor season is as much a safety measure as a cosmetic one.
Timber or composite?
Timber decking — work across the grain with the fan nozzle, never along it; softwood is more vulnerable than hardwood; apply decking oil or preservative after full drying. Composite decking — check manufacturer's guidance for maximum pressure; use a fan nozzle; work along the board direction (opposite to timber); a stiff brush along the grooves before washing loosens embedded contamination.
What you need
- Pressure washer — V-TUF V3 at 150 bar, or V-TUF V5 for larger decks
- Fan nozzle (25° or 40°)
- Decking cleaner with biocidal action
- Stiff brush — for composite deck grooves before washing
- Decking oil, stain or preservative — for timber after washing and full drying
How to clean your decking
Apply decking cleaner and allow 15 minutes dwell time. For composite, work a stiff brush along the grooves before washing. Use the fan nozzle: on timber work across the grain in smooth overlapping passes; on composite work along the board direction. Rinse thoroughly from one end to the other. Allow to dry fully before replacing furniture. For timber, apply decking oil once the surface is completely dry — two thin coats give better penetration than one heavy coat.
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