Due to their low cost, canvas canopies have become an increasingly popular way of roofing a gazebo. Since the canvas is exposed to the elements all day, every day throughout the year, it naturally becomes a magnet for dust, grime, mold and mildew. Cleaning your gazebo canopy once or twice a year will keep it looking good and protect your investment at the same time.
Pick a warm, sunny day to clean your canopy. This will help it dry more quickly, and therefore prevent your cleaning from potentially causing more mold and mildew to grow on the canvas.
Knock off loose dirt and debris from both sides of a canopy with a push broom.
Pour 4 gallons of water into a 5-gallon bucket and add 4 cups of borax. This is your cleaning solution. You will probably require more than one bucket's worth of the solution to clean an entire gazebo canopy, so be liberal with the solution and make more as necessary.
Get up on the canvas and apply your cleaning solution to the entire inner surface of the canopy with a sponge. Let that sit for 5 minutes and then scrub especially dirty, mildewed or moldy areas with more cleaning solution and a plastic-bristle scrub brush.
Rinse the inside of the canvas canopy with a hose.
Repeat Steps 4 and 5 on the outside of the canopy.