Originally Posted by happy2bretired
If the dark streaking is mold, would covering it up with a new metal roof cause problems on down the line? Also, if the metal roof is installed over existing shingles, how can the condition of the actual wood under the shingles be inspected for any damage or deterioration?
Originally Posted by HFWR
Maybe it's just me, but I would never do a roof-over. I want my new roof on solid decking.
Roof-overs are standard with regular shingles. One roof-over, then a tear-off the next time. Doing a tear-off pretty much doubles the cost, and isn't necessary unless a problem is detected.
I don't know if they put metal over asphalt shingles. I'm just guessing here, but if they do roof over the shingles I don't think the mold will be an issued. It's all outside. You can check the condition of the sheathing from the inside, but an experienced roofer can tell a lot just by looking at the condition of the existing shingles. By the way, my brother was a roofer, and I helped him on side jobs a couple times. Not enough to make me an expert, just enough to be dangerous if you listen to my opinion.
Also, just fyi, they have fungicide sprays that can be applied to the black streaks and shingles. I've read fairly good things about the results.