Issue #54 September 1, 2001

Roofing Stains

On June 23rd this newsletter was two parts one about sagging floors and the other about white roofs. One thing about this business is that I am constantly learning every day. To have all of the knowledge really needed for home inspections on homes built from the beginning of time to the present is an absolute impossibility, but those of us in this industry try to do the best we can with the information we have. Some of us have more or less knowledge than others, depending on our training, background and experience and some fools like me stick our neck out there by writing things like this newsletter. 

All of that being said this is one of those, I screwed up letters. Now you will understand why I have all of those disclaimers on what I write. If I am convinced I told you something that may have been misleading or down right wrong, I will be the first to step up to the plate and correct my short comings. A few have demanded such from my last newsletter on radon test placement, but I don't think that's going to happen unless there is someone out there who tops the EPA. 

In my June 23rd newsletter I made reference to a 2" wide metal strip which had been nailed to the top of the roof slope to prevent stains. This strip was improperly installed and the exposed nails will leak, the magic solution which had supposedly been applied to the roof to prevent stains is bunk (unless I learn different later), and the lady was ripped off by what she had to pay for the work. But, I made some pretty strong statements about these issues. After reading an article entitled "What's up on the roof? How to cope with an unwelcome streak of bad yuck." by A. M. Hennessey in the August issue of North Carolina Builder magazine, I need to back up and correct my position on this metal strip and roof stains, and share with you additional helpful information on roof stains. 

I am sure you have noticed those ugly black stains on your listings, the homes you are showing, your neighbors or possibly your own home. According to the article mentioned: "The problem isn't mildew, as most people think, or dumped fuel from airplanes or accumulated dirt or a funky fungus. It's a hardy type of algae found on rooftops throughout much of the United States. It thrives in warm, humid environments, with the most severe problems found in the Southeast, Middle Atlantic and Pacific northwest." I am going to make an attempt to summarize the information made available without outright plagiarizing it, but credit for the information is the articles authors and not mine. 

The most common is a blue-green variety called Gloeocapsa magma (when I read that name I knew this guy must know what he is talking about or he has a creative imagination). This algae may have been present for months or years before you notice the dark pigment it produces to protect itself from the sun. This dark stains are a buildup of generations of dead algae cells which usually begins on the North side or where shade or moisture support its growth. Gloeocapasa feeds on the asphalt shingle filler, calcium carbonate which has been increased over the years contributing to this increase in algae staining. 

As this stain grows its spreads from roof to roof infesting whole neighborhoods and effects most types of roofs including tile, wood shake, concrete, clay and asphalt. Think you can solve it by using a dark roof, think again, it infects and shows up on dark roofs as well. Roof algae are visible on all roof types and all shingle colors. 

This algae does not directly damage the roofing but the dark streaks absorb heat from the sun, causing the shingles to deteriorate faster. This staining is the number one appearance-related problem reported to roofing contractors.

What can you do about it?

Cleaning is a quick fix, must be done every year to minimize staining, is costly and may damage the roofing and shorten its life or damage shrubs. 

The best option is the use of asphalt shingles with metals such as zinc and copper granules, coatings or metal strips (and I said they wouldn't work!!). Many roofing manufactures provide such shingles, but they are more expensive and require replacing the roof to prevent staining. 

From here I am going to quote. These are A. M. Hennessey's words so we hope he is better informed than me when it comes to those "metal strips.":

"If you have a client who has an algae problem but won't agree to reroofing, many in the field recommend Shingle Shield Roof Cleaner, which is specifically designed to clean roofs prior to applying zinc roof protector strips. A power washer can speed up the process, but a maximum pressure setting of 500 psi should be used so the shingles aren't damaged."

"In most cases, one row of zinc strip at or near the ridgeline will inhibit (not kill) the algae growth. (Be forewarned, though. While the zinc works as an algae-inhibitor, it can display what is known as 'white rust' on the original shingle color.) On roof slopes longer than 20 feet, or roofs with a severe or persistent problem, install a second row halfway down the roof. Additional pieces should be placed below dormers, chimneys or any other obstruction that blocks the flow of rainwater from the ridgeline. A dab of roofing cement or polyurethane caulking over the nail head will ensure a watertight seal."

(A.M. Hennessey is a freelance journalist living in Pungo, Va.)

End of quote.

I don't make a practice of recommending products or suppliers, but the magazine gave the following information which may be of interest to you and your clients:

"Editor's note: Shingle Shield zinc strips are sold through roofing and building supply stores such as Lowe's and The Home Depot. To find a dealer near you, call Chicago Metallic at (800) 323-7164. Although select branches of Ace Hardware have been known to carry the liquid roof protector, your best bet is to call K & B Building Products in Albertiville, Ala., a company that distributes Shingle Shield products nationwide, at (800) 776-9830."

The North Carolina Home BUILDER is the official publication of the home building industry, North Carolina Builder is published monthly for the members of the North Carolina Home Builders Association, P.O. Box 99090 Raleigh, N. C. 27624-9090, Raleigh, N.C. Complete credit for the information provided in this article is given to this magazine and the author of the original article Mr. A. M. Hennessey of Pungo, Va. you can contact the Home Builders Association at (919) 676-9090 or visit their web site at http://www.nchba.com/.

Thought for the week

"Even if you are on the right track, you'll get run over if you just sit there"