While best results from users were those used on vinyl siding the manufacturer also claims it is effective on wooden and metal surfaces and especially roof shingles.
Metal siding washer.
Best siding roof cleaner.
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Using too much pressure can dent your steel siding or damage the paint.
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Make sure to use the power washer on the lowest setting it has.
Steel has different cleaning requirements than wood or vinyl.
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Vinyl siding cleaner is commonly applied in three ways.
It will definitely remove the dirt but the paint as well.
Here are the specifics.
Use your pressure washer to get to all the cracks and crevices you could not reach with the brush.
Via a pressure washer through a cleaning bottle with a built in applicator or manually with a long handled brush.
Chemicals you might use on wood or vinyl siding can cause damage to steel.