Fence panels take a real battering from algae, moss and general weathering, especially the shaded side that never quite dries out between rain showers. Cleaning them properly is straightforward, but the pressure setting that works fine on a driveway will shred softwood fence panels if you're not careful.
This guide covers safe pressure for timber fence panels, and why treating the wood straight after cleaning matters as much as the clean itself.
Why fence timber needs low pressure
Fence panels are typically thin, relatively soft softwood, sometimes pre-treated but often not sealed to any great depth, which means they're far more vulnerable to pressure washing damage than decking or structural timber. High pressure held close can strip the wood's surface fibres, leaving a fuzzy, roughened texture, or blast straight through thin panel sections entirely, particularly on the thinner, overlapping lap-style panels common on most residential boundaries.
Keep pressure low, well under what's used on hard landscaping, use a wide fan nozzle, and keep the lance moving steadily rather than dwelling on any one board. Working with the grain rather than directly perpendicular to it also helps avoid forcing water into the wood fibres, and gives a more even finish across the panel too.
Dealing with algae and green staining
The green staining common on shaded fence panels is algae, and like most exterior algae, pressure alone tends to just knock the visible layer off while spores remain in the wood grain. A mild fence and decking cleaner or diluted biocide solution applied first, left to dwell briefly, then rinsed gently, gives a more thorough and longer-lasting result than pressure alone, particularly on rougher-sawn timber where the surface texture holds onto spores more readily than a smooth, planed board would.
Avoid neat bleach on fence timber, since it can bleach and damage the wood surface unevenly, particularly on panels that already have visible weathering, leaving a patchy, blotched appearance that's harder to correct than the original algae staining.
Why treating straight after matters
Cleaning removes algae and grime but also strips away any existing wood treatment or protective layer, leaving bare, freshly-exposed timber more vulnerable to moisture absorption than before it was cleaned. Applying a fence treatment or preservative once the panels are fully dry, ideally within a few days of cleaning, seals that vulnerability back up before the next spell of rain gets into the grain.
Skipping this step is a common reason fence panels seem to need cleaning again sooner than expected: without fresh treatment, the timber absorbs moisture faster and grows algae back more quickly than it would with a protective coat applied, sometimes noticeably so within a single wet North East winter.
Costs and timing
DIY fence cleaning costs little beyond a cleaner and treatment product, while professional fence and timber cleaning typically costs around £3-£6 per panel or is priced per linear metre for larger runs. Late spring through early autumn is generally the best window, giving treatment plenty of dry weather to cure before winter.
Gates and posts are often overlooked in a fence clean but weather in exactly the same way as the panels either side, so it's worth including them in the same pass rather than treating them as an afterthought, particularly on load-bearing posts where rot caused by trapped moisture can eventually affect the whole fence line's stability.
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