Stains on your roof?? And other houses' roofs??

OK, my Mom is going bonkers over this one... Does anyone know WHY so many roofs of houses are stained?? Anyone notice this? It seems like more and more lately - and I've been noticing it for the past couple of years.

We were looking at houses last night and my Mom kept saying why is this happening? We noticed it on houses where it was not caused from a drain, the house had NO trees around it, etc. Just RANDOM staining. Like long black streaks going down the roof.

Why only in the last few years? Why so much more lately? HOW do you get rid of it? And more than anything - what in the world is causing it?

Re: Stains on your roof?? And other houses' roofs??

we have that too.. but its only on the backside of our house.. its the weirdest thing!
i notice it more on slanted roofs like Capes. (mine) it bothers me!!!

Re: Stains on your roof?? And other houses' roofs??

very odd. i haven't noticed but will keep a look out now. total stab but since you said it is somewhat of a recent occurrence, could it possibly be from tree spraying (either personal company or county)?

Message edited 7/8/2009 12:50:51 PM.

Re: Stains on your roof?? And other houses' roofs??

yep very true, like all things they really don't make things like the used to. You can powerwash the stains out.

Re: Stains on your roof?? And other houses' roofs??

Ive noticed this too and have always wondered the same thing!

Re: Stains on your roof?? And other houses' roofs??

I've always noticed that. Main reason I chose a dark roof when we redid ours.

Re: Stains on your roof?? And other houses' roofs??

possible minerals/chemicals in the rain??
repeated rainfall etc could cause it

Re: Stains on your roof?? And other houses' roofs??

Ours is a light grey roof and has stains in some areas. When we redo our roof we will go with a darker roof, probably black.

Re: Stains on your roof?? And other houses' roofs??

Ours has rust stains from our chimney cap. The cap was replaced but we still have stains. We may try power washing but it's a delicate process (don't want to destroy the roof).

Re: Stains on your roof?? And other houses' roofs??

The black streaks are algae-growth.

click on #1

Re: Stains on your roof?? And other houses' roofs??

Re: Stains on your roof?? And other houses' roofs??

We have the black streaks also on our cape. If we do a dormer we will be getting a darker colored roof, but not black. Many contractors have told us that black roofs do not last as long as other colored roofs. I am not sure why though.

You cannot power wash your roof - because the pressure will make the roof come apart

Message edited 7/8/2009 4:16:50 PM.

Re: Stains on your roof?? And other houses' roofs??

I don't know about random streaks, but we have a stain that runs from our chimney down a bit and most of the houses in our area have it.
It's soot stain - generally in homes with oil heat - that runs down the chimney onto the roof. There isn't much that can be done about it and I certainly wouldn't powerwash my roof since that would do more harm than good in the long run.

Re: Stains on your roof?? And other houses' roofs??

Re: Stains on your roof?? And other houses' roofs??

If anyone needs a power washer recommendation, I can fm it to you. Thanks :)

Re: Stains on your roof?? And other houses' roofs??

When we saw our house, I asked the same question and got the same answer as a PP said - algae growth.

Although the staining is only on the north-facing side, it is complete from left to right. The previous homeowner did say that there were more trees but he had them cut down.

It makes sense that it would be only on the north side, since the sun is strongest on your southern exposure. I did notice since we had all the rain that the side under my oak tree has some green algae on it.

We are biding our time till we can extend the house and do a new roof. I know it needs to be done, but we don't want to do it now and then do a section over again when we do construction.

Re: Stains on your roof?? And other houses' roofs??

i have seen this too and was told it was fungi traveling in the air from house to house ??

...i have been told that power washing is risky on roofs.

Re: Stains on your roof?? And other houses' roofs??

We have this algae on the steepest slope of our north facing roof (a Levittown cape) and it bugs the crap outa me everytime I drive up to the house.

The fella's over at Ask this Old House recommend a 50/50 mixture of water and bleach to wipe out the algae (see: Getting Algae and Moss Off the Roof)

May try it this weekend.