Green and Black Mould on a Vinyl Fence
A white vinyl fence shows every bit of growth, and it almost always goes on one side first — the shaded side, or the side your sprinklers hit.
Why fences grow so readily
A fence is shaded on one face for most of the day, sits at ground level where humidity is highest, and is usually surrounded by grass and planting that hold moisture against it.
Vinyl is not porous the way stucco is, so growth sits on the surface — which is good news for removal. But the surface holds a fine texture that gives spores somewhere to settle, and once established the colony spreads along the panel.
White vinyl shows it far more than tan or grey, which is why the same growth on a neighbour's darker fence can look like nothing at all.
The sprinkler line
The single most common pattern we see is a green band along the bottom two feet of a fence run, sharply defined at the top edge.
That is irrigation. A head throwing onto the fence several mornings a week keeps that band permanently damp and feeds it mineral-rich water. It will regrow within weeks of any cleaning while the head is still pointed there.
If your fence has a clean upper section and a green lower band that stops abruptly, adjust the sprinkler before you book anything. Otherwise you are paying to clean the same band repeatedly.
What not to do
Do not pressure wash vinyl fencing. Panels are thin and unsupported between rails. Pressure flexes them, can crack older brittle vinyl outright, and forces water into the hollow posts where it sits.
Do not use a stiff brush along the grain. It scratches the surface, and the scratches hold dirt permanently so the fence looks dirty even when clean.
Do not treat only the visible face. Growth on the back face will re-seed the front within a season.
How we clean it
Soft washing, both faces, full runs rather than patches. A cleaning solution kills the growth at the root and is rinsed at low pressure, so the vinyl is never flexed or scratched.
Post caps, rails and gate hardware are done as part of the run, and we rinse the planting either side before and after.
A soft-washed vinyl fence typically stays clean for a year or more — unless irrigation is hitting it, which we will point out if we see it.
Questions we get about this
Why is only the bottom of my fence green?
Can vinyl fencing be pressure washed?
Do you clean both sides?
Will it damage my grass or planting?
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