If this doesn t work you can sand the pergola and apply a fresh layer of stain and sealant.
How to clean pergola roof.
Regular clean ups will ensure that these stains are tackled and your pergola looks elegant all through the year.
You want to keep the bleach concentration low to avoid staining or damaging the wood.
Leave it on for a few minutes and use a brush to gently rub the stains off.
Gently wash your pergola with soap and hot water in sections.
If it needs cleaning you can use a low pressure power washer to clean away any debris or mud.
Rinse immediately after each section.
Mildew and mold can be cleaned with a mixture of bleach and water.
Take a garden hose and give the entire aluminium pergola a good hosing down from top to bottom.
But your hard work will pay off.
How to clean an aluminium pergola.
Most manufacturers and installers seem to recommend to clean your polycarb roofing pretty regularly with warm soapy water and a soft brush.
To remove stains and mildew mix a cup of vinegar oxygen bleach with a gallon of plain water and apply it on the stains soon after hosing down your pergola.
Here is a link for the thompson s water seal i used.
In a bucket combine some cold or warm water with some liquid dishwashing soap the kind you use for washing.