I have a large and steep roof with moss on the north side, the roof is about 20 years old and has never been cleaned. I requested estimates from what appears to be the two leading companies on Angie's list, 'Margarets' and 'Centsible Services', I will to some extent address both so you can evaluate my thinking process. It should be noted that they both take different approaches to the cleaning process and this might be a deciding factor for you. They both came out on the same day I contacted them. The 'Margarets' representative appears to be a marketing person, he did not strike me as someone who would be getting his hands dirty, let alone climb up on the roof. I determined two things from this, first that I was not interviewing the person who would do the actual work, and second that the price would have to include the cost of management overhead. Representing 'Centsible Services' was Jeff who owns and operates his own company and therefore does the work. Regarding cost, 'Margarets' wanted $900 and would need to come out twice. But since the roof is steep, anchors would have to be first installed by a Roofing Company. A Roofing Company wont even show up for less than a $100 and then add additional charges for each anchor, the roof required 5 anchors. 'Centsible Services' would charge $600 to clean the roof, and $100 to install the 5 anchors, which he would do himself. You probably know by now that I went with 'Centsible Services'. The owner, Jeff, was pleasant, seemed intelligent and gave a sense of competence. When we spoke I asked if he would let me know if there were any areas that needed the attention of a roofer, we get a hard wind out of the north and I have had to have small pieces of roofing replaced in the past. Jeff said he routinely carried extra roofing material with him and would take care of anything he saw. That of course also weighed in his favor. But ----, when he finished he asked if I would pay him then while he was there, and he would email me an invoice when he got home, that is never a good sign but it appeared he had done a thorough job, and I 'mistakenly' wrote him a check. After he left I found that he must have dropped some heavy piece of equipment because there was a 1" by 3" chip out of my driveway laying about where the side of his pickup would have been, something he neglected to tell me. Then I found a 8" square piece of roofing laying on TOP of my water hose directly under the faucet he had hooked his pressure washer to. He had to have seen it when he disconnected his hose, as well as when he blew it loose from the roof. Several other smaller pieces were laying on the ground all around the house. I had neglected to ask him if he had seen anything that needed attention, and he certainly didn't volunteer anything, now I'm concerned about rain damage this winter because of him. When I saw him spraying the loose 'sand? from the roof' off of the back sidewalk, I opened the door and asked if he was using clean water, not water with the chemicals he had sprayed on the roof, because my cat will drink from any puddle of water it finds, and the spray was forming puddles in the lower areas. He assured me it was clean water. A couple days later when I was in the back yard I noticed that there were a lot of brown splashes on the side of my house where the faucet is. A rectangular area about 3 foot by 8 foot, that won't clean off. Jeff apparently cleaned his equipment back there and got the chemicals all over the house and the sidewalk. This means I'm stuck with the mess until the next time I have the house cleaned and I don't know about the sidewalk if pressure washing will remove the brown stain. AND, it means that he might have been using clean water, but the puddles would have had the chemicals that he washed out of his equipment. He would rather take a chance of my cat dying than my knowing what a mess he was making. I'm quite certain he did not disconnect the down spouts, so the heavy material that washed loose from the roof must have gone down the spouts and is now laying in the drain system partially clogging it. All in all, not satisfied, and concerned about damage he might have done, not only to missing roofing material, but I also wonder if he was smart enough to use very low pressure when spraying, there is still a lot of 'sand?' laying on the ground where he didn't bother to clean up.