The laserlite polycarbonate sheets on my pergola roof are looking a bit grubby and have built up dirt and grit over time. We use our outdoor entertaining area quite a lot in summer time and it doesn't look great when you look up and see the build up. Does anyone have any suggestions on what is the best way to clean this material? We've tried to use a pressure hose which hasn't worked as well as we'd like - plus the pergoa is quite high and hard to get to (in the centre especially) without an appropriate ladder, making it difficult to reach all areas to clean. We've considered going up onto the roof to scrub with a broom as well as clean with a pressure hose, however i'm concerned that after years of sun exposure the materials might be brittle and break. I'm guessing the laserlite is approximately 10 years old. Would love to hear your suggestions!