Black roofing stains


I live in the Williamsburg area of Virginia and am on a committee of our homeowners association. Some of our homes have a black algae or mold stain on the north side of their roofs. from what I have read the best way to remove the stain without damaging the roof is via an oxygen bleach. The prevention of recurrence seems to be another matter. I have read that installing zinc or copper strips at the peak of the roof will help but in another article it said that won’t help much unless they are installed when the roof is installed. I would like to advise our homeowners of a good way to deal with the problem in a way to minimize cost and also to prevent its recurrence. Any suggestions???


do you have a gutter from aluminium. Than it cupper not good idea.


In my opinion the best way to solve this problem is to replace the roof with a high quality algae resistant shingle and also go with a dark color. As far as washing the roof, this I do not reccomend because it could wash away granules therefore the shingles will not last as long. Please consider hiring a contractor with a good reputation in roofing to solve this problem,and not mister handy pressure washer which could result in problems worse than just cosmetics.


I have the AR shingles and they still do it after about 6 yrs. I used a product called spray and forget and it works great.Look it up on Google


Three years ago I did a roof that had zinc strips on it which had non AR shingles.

The home owner got sick of looking up at his black shingles while sitting in his pool so he decided to try to cure the problem.

He hired a contractor to come out and spray the North side of the roof with the three part chemical system which worked for a while. The algea came back at which time he had a roofer install zinc strips. Within a few months the staining was long gone. The North roof looked great for a couple years until the South side failed due to being organic shingles.

When we put on his new roof we re-used the zinc strips.

A friend of mine who works a lot with insurance claims saw a roof hit by lightening in which the lightening strike ran along the zinc strips and popped all the ridge off as it ran along the peak.

I have put zinc strips on since then without doing any other treatment and it’s worked great for removing staining.


How old are the shingles or the roof itself?

Depending on the age, you can purchase products (mentioned above) which can be sprayed with a Hudson (garden) sprayer. Let it dwell, and then rinse.

The zinc strips can be used AFTER the roof has been cleaned. They do not work very well without cleaning first. It should be mentioned however, the strips installed directly below the ridge line are unsightly in my opinion.

There is another problem. Once cleaned the fungus and algae WILL come back in a couple of years if you do not use the zinc strips.

Today’s shingles will have a 10-year fungus/algae resistance warranty. The copper and zinc oxide granules do a very good job during those 1st ten years. However, after that period expires the northern exposure/slope will start to show the stains.

Hope that helps and
Good Luck.


hey meki,
nice to see germany in the house.

ditto everyone.



Call Preston construction. He is a local guy. He does the work at Busch Gardens. Nice guy and a very roofing contractor. 592 5507


It’s been my experience that the black algae growth is not always actually algae and is sometimes granular loss. There are various products on the market which claim to remove the algage on the roof when introduced with moderate pressure, not high pressure. The point being let the chemical do the work and disolve or cleak or kill the algae then a light rinse to remove the chemical.

As far as copper or zinc strips go, I personally feel they need to be installed at more than just the ridge. You may consider installing them half way down the rafter as well.

When all is said and done, none of these solutions can be warranted. If the customer really desires a warranty, sell them new shingles with the AR and a 10-15 year warranty against algae depending on manufacturer.


Shingle shield moss and algae remover.
You can get it at your local shingle supplier.


The chemicals like spray and forget will work, but it takes time for the effects to be seen. Zinc strips also work, but you may have to install several rows depending on your roof configuration and size. More importantly, if you are anywhere near Colonial Williamsburg I suspect you are going to have some pretty tight building restrictions. The fact you have shingles instead of slate tells me you probably have a little leeway.


Simple and easy fix, guaranteed to work. Use a mix of bleach and water, sprayed with a garden sprayer, on the entire roof on a day when you do not expect rain or direct sunlight. Let it sit for a day and rinse the roof the following day. This process may need to be repeated occasionally (every year or so), however it is an easy and effective alternative to strips or expensive cleaners. Strips are a sham in my opinion, I live in the Northwest and they ALWAYS leave striping in the roof which makes it even uglier than the stripping itself.


April, what ratio do you use for the bleach and water solution?



Tallman: it really doesn’t take much bleach. Try just a cup of bleach for each 3 gallon sprayer bottle. Use as little bleach as possible to decrease impact on the environment, don’t forget your downspouts run to your lawn and garden most usually.


the problem is the bleech water can prematurely dry out the shingles and shorten there life.


APRIL, the girl roofer?

first post?

nice to meet you?



It didnt take gweedo long to self introduce… :slight_smile: