What Happened

[dirtdobber]

Recently cleaned a roof that had a good amount of algae discoloration. After the roof dried I came back to take some after pictures. The roof looked good except under the dormers where the roof actually looked cleaner or lighter colored than the rest. I don't know if it is actually cleaner there and the rest needs another application or if it is some sort of discoloration from the windows like a paint chalking that has just bled into the shingles. Anyone ever seen anything like this before? Attached are some before and after photos so you can see my delimma.

[Apple Roof Cleaning]

Originally Posted by dirtdobber

Recently cleaned a roof that had a good amount of algae discoloration. After the roof dried I came back to take some after pictures. The roof looked good except under the dormers where the roof actually looked cleaner or lighter colored than the rest. I don't know if it is actually cleaner there and the rest needs another application or if it is some sort of discoloration from the windows like a paint chalking that has just bled into the shingles. Anyone ever seen anything like this before? Attached are some before and after photos so you can see my delimma.

Yes, we see it often.
The sides of the dormer protect the shingles from the elements by shading them, and sheltering them from wind.
As a result, they look more like new shingles then ones exposed more to the elements.

[dirtdobber]

Originally Posted by Apple Roof Cleaning

Yes, we see it often.
The sides of the dormer protect the shingles from the elements by shading them, and sheltering them from wind.
As a result, they look more like new shingles then ones exposed more to the elements.

Wind? Did you mean sun? Why isn't it darker if it is shielded and rest of the roof lighter colored due to the elements? What do you tell the customer?

[dirtdobber]

Obviously I haven't mastered posting photos. Don't know what went wrong with them either!! Take my word for it though, the roof was cleaned and the shingles directly below the dormers are lighter colored between the bottom of the dormer and the gutter, the width of the dormer...

[Don Phelps]

What mix did you use?

[Apple Roof Cleaning]

Originally Posted by dirtdobber

Wind? Did you mean sun? Why isn't it darker if it is shielded and rest of the roof lighter colored due to the elements? What do you tell the customer?

Asphalt is BLACK, what determines color is the granules.
IF the granules are starting to fall off the unprotected areas of the roof, the roof will look darker in those areas.
Conversely, the protected areas of the roof may look lighter, since granule loss could be less in those areas.
I am not there, but that may be what you are seeing.

[dirtdobber]

Originally Posted by Don Phelps

What mix did you use?

I wish my pictures came out better but to answer your question I used 15 gal bleach, 38 or 40 gal. of water ,2 bottles of dawn and about 11 cups of TSP.

Actually if you look at the pictures as they appear in the link without clicking on them, the first photo is a before picture that really doesnt show alot of staining ( but there was alot). The finished product looked alot like the first photo without the algae staining but with the lighter colored shingles below the dormers but not quite as obvious.....Does that even make any sense?!!

[Apple Roof Cleaning]

Look what I found ?
Causes & effects of the loss of protective mineral granules from asphalt roof shingles or roll roofing

[Don Phelps]

Originally Posted by dirtdobber

Recently cleaned a roof that had a good amount of algae discoloration. After the roof dried I came back to take some after pictures. The roof looked good except under the dormers where the roof actually looked cleaner or lighter colored than the rest. I don't know if it is actually cleaner there and the rest needs another application or if it is some sort of discoloration from the windows like a paint chalking that has just bled into the shingles. Anyone ever seen anything like this before? Attached are some before and after photos so you can see my delimma.

Where did the 2nd pic go?

[dirtdobber]

Originally Posted by Don Phelps

Where did the 2nd pic go?

I tried to fix the sorry pics and ended up losing one

[jon chapman]

I have to agree with Chris. With only being able to see the 1st pic, I cant be sure, but if it still looks dark and your sure you put enough mix on it, then the loss of granules will show as darker than the surrounding area. Remember the granules are lighter in color, remove them and you just have the shingle itself.

[dirtdobber]

Just for my peace of mind, I told the homeowners that I wanted to re-do that side of the roof at no additional cost of course. My reputation is at stake! Honestly I hope it cleans up because it just doesn't look good and is a poor advertisement.

[fishgazam]

Galvanized flashing under the dormer at the siding and roof meet causes the algae to die. Galvanized metal is made by afixing zink crystals to metal. as the zink oxidizes the algae beneath is killed. That area of the roof will look better when cleaned because there is nothing to clean there. te other areas have dead algae and chemicals on the roof untill a few good heavy rains. then the roof will look mostly consistant.

This is also how fungal resistant shingles are made. Manufacturers add zink or copper granuals to the ceramic aggrigate on the top of the shingle. when the copper or zink oxodises "sp" it kills any algae there.

Roof should look fine in a month or so.

AC