Power Washing and Roof Cleaning Forum

Let me first start off by saying  "Hi Gary "  I understand he can't get enough of this place and tries to hide his IP with hide your ass or somthing like that.

I have cleaned a handful of slate roofs about two a year and they always looked great after a rain. About two months ago I cleaned an entire house and a garage and left it for the rain. About a week ago the homeowner called to say he believed there were "patches "of lichen still on the slate. Upon inspection I noticed it was not Lichen but a red almost sulfar looking color on the slate on several different parts of the roof front and back and toward the peak. I noticed both sides of the garage roof was perfect. The homeowner has lived in the home about twenty years and was told upon purchase that it was a fairly new roof. With a ladder put up for a closer look these slates were "flaking " and it definitely was not lichen. I did what anyone one of us should do on here, I made a phone call to a fellow member. I called Art who suggested I call Eric from A&E because he has done many slate roofs. Eric called me back { unfortunately I was in the middle of another job and couldn't talk long } he told me that the cause was delamination. He said it was a normal process to the slate caused by the weather,sun and loss of minerals, he said this usually started when the slate get's anywhere between forty and sixty years old. Thanks to this quick information by Eric I felt a little bit more relaxed as you can imagine. I remember reading on "Gary's board " that using alcohol in your mix can cause a white "Stain or streak "to the slate shingles..that is now not true. I did some research this morning and that is actually a sign of ageing of the slate. So this is what I figured out, The roof is probably a little older then first thought. The problem was covered by the dirt and algae. It is a normal process caused over time by weather, the garage roof front and back is in total tree/shade there fore protected from the eliments some what. I did notice it { much worse } on other homes in the area when I left but this little knowledge should be in your head for pricing slate roofs, "what can be under the Algae " I found a quick little sight for some shared reading.   Thank's again Eric sorry I was in a rush but I know you understand.

                     Inspectapedia.com/roof/Slate_Roof_Defects.htm#delaminating

                     Inspectapedia.com/roof/Slate_Roof_Defects.htm#delaminating