When washing houses I run across some staining on the Facia/Eaves which is black and grey in color. Generally it is tin/sheet metal and I have tried many different chemicals and still haven't found one to get it back to bright white.Anyone else have this problem???
I'm guessing that you're referring to areas where run-off from the roof has stained the trim. (This is the same stain that causes streaks on the gutters.) I have found that Simple Green will remove both. Be careful though, sometimes the finish on metal (gutters or wrapped trim) will come off if you are too aggressive. I always point out the situation to the customer so that they can take corrective measures - if possible - or the stains will return.
Be careful, because in some cases there is nothing you can do about it. Often times they use the very cheapest, low quality aluminum and coatings on those surfaces, and you can very easily completely remove the finish if you're not careful.
Try a test patch before you do a large area, preferably on the back of the house, just in case.