Black marks on roof
 

I know this is a one answer thread, but I'm dying to know what causes the black marks on the roof, the one that looks like a black dirt bomb has been dropped....

It's sad to see such a nice looking house and a good roof, but there's just that little droppped-bomb look.

What is it? What causes it? Can it be gotten rid of?

I'd bet it is algae.

Check this link: http://www.naturalhandyman.com/iip/infxtra/infroo.shtm

or this one: http://www.thisoldhouse.com/toh/tvpr...401167,00.html

I'm going to say it's mildew. Strips of zinc placed below the ridge will release zinc oxide and inhibit further growth-you've still got to clean off the existing crud.

Is it just random patches, or near roof ventilation? If random I'd third the fungus thing. Is the roof ventilated? Attic conversions without adequate venting can promote growth of junk. Do you see signs of moss?

If the dark spots are around vents it could be smoke damage. Usually also shows up around the soffit vents.

I had this and it was mildew. I hate to tell you, but i had to scrub it all off, and then put a mildew resistant paint back on, and re stucco the celing. It was a huuuge job :-(

It could be a number of things. The most likely culprit is tree sap. Are there any trees hanging over the roof? Especially ELMS. Those trees are beautiful but they suck. My neighbor has two monstrous elms hanging over our houses. My roof looks like it's been in a fire. :(

The next culprit is mildew or algae. But, if you're getting plenty of sun then you probably don't have that problem.


Just to be sure, we are talking about the roof (exterior) and not the ceiling (interior) right?

terodactyl poop marks. Those damn things fly by drop a bomb on the house. Just be glad the roof held up.

Be careful scrubbing since shingles are easy to damge.

Try spraying first with a water and bleach mix (5 parts water 1 part bleach). If results don't ocur within half an hour increase to 3:1 then 2:1. The bleech should kill the mildew/moss and dry it out. Later you should be able to hose it off or if necessary sweep it off.

I just had to chime in here. I glanced at the headline and thought it said "Black man on roof."

Nearly snapped my neck doing a double take.

Here's another roof-related question. We have a large limb that has fallen on our roof and it is propped up by some electrical line. Part of the limb is on the roof and part of the limb is on the electrical line. How can I tell what type of line it is and whether or not I can move the limb myself without getting fried?

It's usually pretty easy to follow the wire back and determine if it is cable TV or incoming power. Also the cable TV will be one thin black cable usually and the power will be three cables twisted together with one of them most often uninsulated.

aloha.
 

i think black marks on your roof is the same with black algae, it is a stain occur on a asphalt shingle roofs.The roof algae starts as dots, then takes a cone shape and can eventually cover your entire roof! Introduce copper or zinc strips to kill roof algae. You can also use Oxygen Bleach.