Waterproof canvas is typically used on boats as well as other similar outdoor surfaces. The heavy duty canvas does not absorb water, so you avoid some of the mould and mildew problems which are common with other types of outdoor materials. Waterproof canvas needs cleaned just like any other fabric, so clean the canvas as you see fit with a mild solution that removes build-up without deteriorating the canvas.
Rinse the canvas regularly with your hose. Do this on a warm, sunny day when possible, as this allows the water to air dry quickly.
Mix a 50/50 solution of water and white vinegar in a spray bottle. Spray this over the waterproof canvas. The vinegar disinfects and deodorises, plus gets rid of any mould or mildew growth. While mould and mildew are not typically an issue with waterproof canvas, the elements can sometimes build up if the canvas is subjected to standing water for long periods of time.
Mix 1 gallon water with 2 tbsp washing powder. Dip a sponge in the bucket and scrub down the canvas to remove bird droppings and other residue built up on the canvas.
Rinse the waterproof canvas with your hose once more and allow it to air dry.