Here is a slate roof we treated last summer in Langdon New Hampshire in Cheshire county. Just recently were we able to get the After treatment pics. Slate roofs are extremely expensive to replace and to repair. This roof has New England purple slate which is $12 per slate-new and $6 per slate used. It makes sound financial sense to have your New Hampshire or Vermont slate roof cleaned professionally saving you many thousands of dollars. We can turn your black streaked moss covered into the beautiful slate roof that was meant to be shown and protecting your home.