Looking up at your roof and seeing ugly black streaks?! You are not alone! Your roof is the first step in protecting your house and keeping it safe and dry. As such it is exposed to all sorts of the elements ranging from rain and snow all the way up to mold, algae, and moss.
Like anything else, roofs need to be regularly cleaned and maintained to perform and function as long as they can. This quick start guide will show you to get rid of black streaks on your roof fast and keep them off.
What are black streaks on my roof?
Black streaks are a cyanobacteria known as gloeocapsa magma. It tends to grow in wetter climates and areas of high humidity. You can see it on almost any roof that hasn’t been cleaned and washed recently.
Black streaks also include moss, algae, and black mold or anything else that is growing on your roof and shouldn’t be. Not only is it ugly but it can alsi
In virtually any climate, roofs get all this stuff from trees and wind blowing spores all over the place that land on your roof and when left untreated, can wreak havoc on your roof life.
First steps to proper roof care
Most roofs have a lifespan of between 20-40 years. A roof that isn’t properly cleaned might see 5-10 years taken off its roof life.
As such it is crucial you keep up on the maintenance just like any other part of your household, roofs need regular care.
To start, as beautiful as trees are they can cause most of these problems. Trees rain debris such as needles, pinecones, and leaves and also can harbor spores of moss and mold which sprinkle down like little alien invaders.
Even if you do nothing else except keep the debris off your roof and out of your gutters your roof WILL last much longer.
Keep trees trimmed back and don’t allow them to touch your roof or home. Keep your gutters clear and flowing as they should so water can flow away. You do not want water leaking inside your home as this can lead to other types of mold growing inside the walls or basement and lead to all sorts of health problems.
Our whole house had a leak earlier this year and we had to have mold remediation specialists come and replace all the walls. Not fun!
Exactly what to use to clean your roof
I have cleaned close to 2,000 roofs at this point over the last 5 years and we use a variety of treatments in different circumstances.
The most common and quickest way for black streaks however, is to use what is called a soft wash which is a mixture of chlorine bleach, water, and soap.
The technical term for most bleach you see at the store is sodium hypochlorite (SH). This is what is used to clean our city drinking water, pools, and it works great for cleaning roofs as well.
Bleach is great because you can mix it up in something as small as a spray bottle or as large as a soft wash tank like I have and as long as you have a good ratio you can start spraying and cleaning your roof or any other surface that has mold, spores, or algae.
How to wash your roof
When people talk about soft washing the term to use is how “hot” the mixture needs to be. This isn’t a temperature thing, it’s a term for how strong your bleach solution needs to be.
That being said soft washing does tend to work better when it is a bit warmer with between 50 and 80 degrees (10- 27 degrees C). Any colder and the bleach has trouble activating and any warmer and the chlorine can evaporate off before working. If it’s cold you can use warm water and if it’s hot you can wet the roof with cold water first to cool it down before spraying.
As far as our cleaning solution I’ve found that to be effective we want a mixture of about 3% sodium hypochlorite to water and about a quarter cup of a surfactant (soap).
Most bleach you see at the store is about 5-6% SH so if you wanted to make a mix of 3% all you would need is one part bleach, one part water and a quarter cup of a surfactant, something like dawn dish soap will work or liquid laundry detergent.
There is a myth that mixing dawn soap in bleach will make mustard gas because people say it has ammonia in it but from my experience I haven’t found that to be the case. Regardless though you should be mixing outside anyways and wearing protective gear such as a respirator/mask, gloves, and eye protection.
Bleach is nasty stuff when not handled carefully. It kills things by destabilizing the cell walls and turning fatty acids and oils into soap, that’s why your hand feels slippery after touching it.
It is also very alkaline and basic in nature which most mosses, algae, and bacteria hate. These organisms tend to grow in more acidic environments.
Anyways all we want to do is thoroughly soak and spray the affected area of mold, black streaks, or moss. I will usually wash the entire roof just to be sure, also because sometimes the spores of mold or moss can be microscopic so you want to make sure you’re soaking the whole roof down and washing it well. I have a quick tutorial on my Youtube channel as well right here.
The good news is if your mixture is hot enough it will die almost instantly, you will see it turn yellow or white. and start to disappear entirely. If there is moss it will start to crumble and turn to dust within a few months. If you’re not seeing anything die yet you will want to add more bleach, sometimes I’ll test my mix on a small area first and make sure it’s hot enough then spray the rest of the roof.
All the organic material on the above roof was dead within minutes!
The next best way to chemically clean mold and moss
Chlorine bleach is the quickest and most effective but isn’t always the best to use for a variety of reasons.
Some people are sensitive to the chlorine and it also is generally considered more toxic to the environment so be careful if you are spraying it on or near any plants or water sources like a lake or river.
I personally like to use an oxygen bleach mixture which uses sodium percarbonate. This when mixed with water makes hydrogen peroxide (H2O2) and sodium carbonate.
This also does a great job of getting rid of a mold problem or moss as it is really good at killing the spores of these organisms. The only thing is it doesn’t bleach as strongly so you don’t get the instant “bleach white” look that chlorine bleach does but give it a bit more time and it is still just as effective at killing everything.
To use sodium percarbonate you want 1/2 cup to one gallon of water and it is best with hot water but I’ve used normal water and it still works just fine. This amount will cover about 150 to 300 square feet so generally I will use between 3-6 pounds to clean one whole roof.
To wash follow the same rules as above and you can bit a bit more lax with the safety gear as this stuff isn’t nearly as toxic. It’s still a good idea to put some safety glasses and protective gloves on but spray away and get that moldy roof clean!
Alternative Methods of cleaning a roof
If you don’t want to spray your roof or perhaps you want to just use what you have at your house there are other methods you can use to clean your roof.
Many, when mixed with rain water will clean the roof for you, although in most instances won’t work as quickly or as strongly as one of the soft wash treatments above.
Laundry detergent, Borax (sodium borate), baking soda (sodium bicarbonate), Zinc moss powder, and white vinegar can all be used as most surface mold or moss lives in a Ph spectrum of around 6 which is slightly acidic.
If we use anything outside of this Ph range we can still hamper any mold or algae growth.
So to use you simply need to just sprinkle these powders on the roof (or spray the vinegar) and let mother nature do the rest. I’ve used just baking soda before when I was right next to the Puget sound and as long as you clean off all the debris and clean out the gutters sometimes that’s all you need.
You might need to apply these powders every few months or at least once a year whereas if you softwash with the sodium percarbonate or sodium hypochlorite you can usually do that less often say every 3-5 years and be fine.
Conclusion
Keeping your roof clean of black streaks which we now know is a variety of different nasty things growing on your roof is as simple as keeping the roof clean and clear of debris and applying the right chemicals.
Using powdered chemicals can work well but the fastest method is amlost always to soft wash your roof with either chlorine (SH) or oxygen bleach (H2O2).
Either way keep your roof clean and if you live in the greater seattle area feel free to contact me or my company HERE and we will take care of ya!