How to Clean a Grey Cedar Fence
To clean a grey cedar fence, apply a wood-safe cleaner to loosen the grey fibres and kill the algae, then rinse at low pressure with a wide fan tip, moving along the grain. High pressure held close tears out the soft wood between the grain lines and leaves a furry, striped surface. Re-stain soon after, while the wood is clean.
A Lower Mainland cedar fence goes grey, then green on the shady side, within a few years. Under the weathering, the original wood colour is almost always still there.
Why fences grey and green
Two things happen at once. UV light breaks down the surface fibres of the wood and turns them silver-grey. Meanwhile the shaded, damp side of the fence grows algae and mildew, which reads as green-black streaking and makes the boards slimy to the touch. Both problems live in the very top layer of the wood.
That is good news, because it means cleaning can restore the colour dramatically, you are removing a thin spent layer and the growth on it, not trying to fix the whole board.
Cleaner first, low pressure second
Wood is soft, so fences follow the same rule as decks: a wood-safe cleaner does the work, not brute force. The cleaner loosens the grey fibres and kills the algae and mildew at the root, and then the fence is rinsed at low pressure with a wide fan tip, worked along the grain and kept moving. The result is even, bright wood with no wand marks.
High pressure held close is what ruins fences, it tears out the soft early wood between the grain lines, leaving a furry, striped surface that then weathers even faster. Once wood is gouged, only sanding fixes it, so technique matters.
Clean now, stain while it is fresh
If you plan to stain or seal the fence, the clean comes first, stain applied over grey, algae-laden wood does not bond well and traps the growth underneath. Clean, dry wood takes stain evenly and the colour lasts far longer. Give the fence a few dry days after cleaning before staining.
Fences are usually priced by length and height. A quick photo or two and your fence's run length get you an accurate free quote, and it is often worth bundling with a deck clean since the crew and equipment are already set up.