TL;DR
Wood fences want a cleaner with dwell time and a brush, not high pressure -- the boards are thinner than deck boards and fur just as easily. Vinyl tolerates more but scratches from abrasives. Metal fences are a rust story rather than a dirt story. And on every material, the green side facing north is telling you about shade, not about your cleaning schedule.
Check the fence before you clean it
Ten minutes of inspection changes what the job should be.
Push on each post at ground level. Rot at the base is the most common fence failure, and a fence with soft posts needs repair before it needs washing.
Look at the fasteners. Rusted nails and screws stain the boards around them, and cleaning will not remove a rust stain that is still being fed.
Note where the growth is. Green algae and moss concentrate on the shaded side, at the bottom where splash-back hits, and anywhere a shrub touches the fence. Those are moisture conditions and they will come back unless you change them.
Trim the vegetation back. Plants pressed against a fence hold moisture against it permanently and are the reason one section always looks worse.
What is the best way to clean a wood fence?
Pre-wet the fence and surrounding plants, apply an oxygen bleach or wood-specific cleaner, let it dwell 10 to 15 minutes without drying, agitate along the grain with a stiff brush, then rinse at low pressure. Keep a pressure washer under about 1,200 PSI with a wide tip if you use one at all.
Wood fences
Fence boards are typically thinner than deck boards and often cedar or pine, both of which are soft.
The method. Pre-wet plants and lawn along both sides. Apply the cleaner from the bottom upward so runoff does not streak the dry board below it. Let it dwell 10 to 15 minutes, misting to keep it wet. Agitate with a stiff brush along the grain. Rinse from the top down.
Cleaner choice. An oxygen bleach product handles greying and mildew and is much gentler on the landscape than chlorine. Chlorine bleach works faster on heavy growth but is harsh on the wood fiber and will damage the plants on both sides of the fence.
Pressure limits. If you use a washer, stay low, use a 40-degree tip or wider, hold it 12 inches or more back, and move with the grain without stopping. Fence boards fur exactly the way deck boards do, and the mechanism is explained in why high pressure ruins a wood deck.
Never mix products. Do not combine a bleach cleaner with a brightener, a rust remover, or any acidic product -- brighteners are typically oxalic acid and bleach plus acid releases chlorine gas. If you are running a two-step system, rinse completely between the steps.
After cleaning. Let the fence dry one to three days before staining or sealing. Finish over damp wood peels.
Vinyl and PVC fences
The most forgiving material, and the one homeowners most often over-attack.
Warm water with dish soap and a soft brush handles routine dirt. For green algae film, an outdoor cleaner with a dwell works well. Rinse thoroughly so no residue is left to attract dirt.
Avoid abrasives. Scouring pads and abrasive powders leave a scratched matte surface that then holds dirt permanently and looks worse than the original film. That is the main way people ruin a vinyl fence.
Vinyl tolerates moderate pressure, but a narrow tip at close range still gouges it and can force water into the hollow rails where it sits. A wide tip at a distance is plenty. The stubborn stains on vinyl are usually rust from an adjacent metal fitting or a sprinkler, and those need a rust remover applied on its own with a full rinse before or after any other product.
Wrought iron and aluminum
Wrought iron. Wash, rinse, and dry, because water sitting at the joints and in the bottom of hollow sections is what starts rust. Remove rust back to sound metal with a wire brush, prime with a rust-inhibiting primer, and topcoat. Do not paint over active rust; it bubbles back within a season.
Powder-coated aluminum. Mild soap and a soft cloth only. Abrasives and solvents damage the coating, and once the coating is broken the aluminum oxidizes at that spot into white chalky pitting. Touch up chips promptly.
Neither material should meet a close-range pressure stream, which drives water into hollow sections and under coatings.
Masonry and stone fences
Brick, block, and stone walls are a low-pressure job because the mortar is deliberately softer than the units. Detergent with a dwell plus a bristle brush is the method, and the rinse should never be aimed straight into a joint. The overall approach is the soft wash logic described in how soft washing works.
Protecting the plants on both sides
A fence has landscaping on two sides and both are in the runoff path.
Pre-wet everything with plain water before applying anything, and rinse the beds again afterward. Cover anything delicate. Chlorine bleach solutions in particular will burn foliage, and a fence line is a narrow strip where the runoff concentrates rather than dispersing.
This is worth mentioning to a neighbor before you start on a shared fence, since the far side is their planting.
How often, and what makes it come back
Once a year suits most fences, generally in spring. The shaded side and the bottom foot will always be the first to green up again.
The durable improvements are not cleaning-related. Trim shrubs back so air moves, adjust sprinklers that hit the fence, and keep mulch and soil from being piled against the boards. A fence with airflow stays clean two to three times longer than one with a hedge pressed against it. For pressure limits by surface, see what PSI each surface can take, and for how fences sit alongside the rest of the exterior, the exterior surface cleaning overview.
FAQ
Can you pressure wash a wood fence?
Carefully, at low pressure with a 40-degree or wider tip held at least 12 inches back and moved with the grain. Fence boards are thinner than deck boards and fur easily, leaving a splintery surface that holds dirt. A cleaner with dwell time and a stiff brush is the safer method.
What is the best cleaner for a vinyl fence?
Warm water with dish soap and a soft brush for routine dirt, and an outdoor cleaner with a 10 minute dwell for algae film. Avoid abrasive pads and scouring powders entirely, since scratches in vinyl hold dirt permanently and look worse than the film you were removing.
How do I remove green algae from a fence?
Pre-wet the plants on both sides, apply an oxygen bleach or outdoor cleaner, let it dwell 10 to 15 minutes without drying, agitate with a brush, then rinse. Algae returns wherever the surface stays damp, so trimming back vegetation and fixing sprinkler overspray matters more long term.
Will bleach damage my plants along the fence?
Chlorine bleach runoff will burn foliage and can harm roots, and a fence line concentrates the runoff into a narrow strip rather than dispersing it. Pre-wet with plain water, keep the mix weak, and flush the beds afterward. Oxygen bleach products are considerably gentler.
How do I stop a metal fence from rusting?
Dry it after washing, particularly at joints and the bottoms of hollow sections where water pools, and touch up chipped coating promptly. Where rust already exists, brush it back to sound metal, prime with a rust-inhibiting primer, then topcoat. Painting over active rust always bubbles back.
Should I stain a wood fence after cleaning it?
If you plan to, wait one to three dry days first, since finish applied over damp wood peels and blisters. Cleaning is what determines how evenly stain absorbs, so a fence washed with a torn, furred surface will take stain unevenly regardless of how many coats go on.
How often should a fence be cleaned?
Once a year is right for most fences, usually in spring. The shaded side and the lowest foot of boards green up first and fastest. Improving airflow by trimming back plantings, and keeping sprinklers off the fence, extends the interval more than any product does.
Fence length, material, condition of the posts, and how much growth has established all change what the job actually takes, and a fence with rotted posts needs repair rather than washing. Get a quote and we will look at yours, or read more about pressure washing services.
