m32825
Well-known member
Central Florida, metal garage with stuff growing on some areas of the roof. Doesn't seem to care if it's in sun or shade. No tree over the patch in this picture. What is it and how do I get rid of it?
How to clean garage roof
- Thread starter m32825
- Start date
Hobby_Man22
Well-known member
It definitely didn't scare off the hurricanes
That is mold or mildew. About all you can do to clean it is pressure wash it. You might get somewhere with a hose and a car wash brush. A mix of detergent and one cap full of bleach to a gallon of water will help cut it and keep it from coming back for a while, but it will come back.
Some zinc or galvanized sheet metal strips fastened to the ridge will keep it from coming back.
Some zinc or galvanized sheet metal strips fastened to the ridge will keep it from coming back.
marinusdees
Well-known member
I would scatter Tide WITH bleach, like a light skiff of snow. The Tide holds the bleach where you put it, the bleach kills the mildew, it will wash off. Don't expect to be able to put the Tide at the peak and it will wash down. It won't. Last Tide I bought, I bought on Amazon. If you want to hurry the process, wet the Tide with a garden hose after sprinkling. After a few weeks, wash the mold off with the same hose.Central Florida, metal garage with stuff growing on some areas of the roof. Doesn't seem to care if it's in sun or shade. No tree over the patch in this picture. What is it and how do I get rid of it?
Solpainter
Well-known member
- Joined
- Oct 27, 2011
- Messages
- 156
Use Wet and Forget. It has never let me down. Just use the proper ratio. May take some time but works.
Big Bad Dad
Well-known member
Please explain how or why attaching galv metal strips to the ridge will keep it from returning??
My slate roof has copper at the roof peaks and the valleys and flashing...
Copper and or zinc are both heavy metals and when exposed to rain will release ions...
The ions are toxic to moss and mildew preventing growth...
This is Algae not mold. Here is how the zinc works and how to clean.
www.thisoldhouse.com
Getting Algae Off Your Roof
Roof algae looks unsightly and can cause severe damage. Read more about how to spot, treat, and prevent it from the This Old House experts.
www.thisoldhouse.com
chad215
Well-known member
looks like honeydew from insects in the trees.
welder4956
Well-known member
I use a product from Lowes called Outdoor Cleaner on outdoor trim and siding. You have to mix it 50/50 with water and put it on with a garden sprayer, then rinse after it soaks in for a few minutes. I set my hand pump garden sprayer on stream and sprayed the aluminum trim on our second floor windows from the ground without using a ladder. I have tried Wet N Forget and while it may work eventually, it took way too long for me.
I was always a bit skeptical of it but the shop on my new house had one really bad section of roof because of trees in that area. The roof is basically like a "+" as the building has a RV bay in the center and 2 standard hight areas on both sides and one of the lower roofs is the problem area. I treated that whole section and about a 4' section along the bottom of the taller roof as a test. The previous section is now the best area and you can see the 4' area I treated of the taller roof and I now need to treat the entire roof.
It does not work overnight but take some before pictures to refer to in a few months.
Thanks guys. I've used Wet and Forget with success on the shingled house, so I'm going to give that a try.
For the copper/zinc strips, it seems like the runoff would keep the "valleys" of the roof clean, but would it do anything for the flat peaks? Also, seems like precautions would be in order to prevent galvanic corrosion.
For the copper/zinc strips, it seems like the runoff would keep the "valleys" of the roof clean, but would it do anything for the flat peaks? Also, seems like precautions would be in order to prevent galvanic corrosion.
Youngandfree
Well-known member
Is your roof painted silver or bare galvanized? Bleach can react with bare galvalume and make it blacker than the algae growth. If it's painted silver you shouldnt have any issue.
Youngandfree
Well-known member
As long as paint is in good condition, using a bleach product "should be fine". You can get some household bleach that's around 6%, and dilute it 50/50 in a pump sprayer. Spray it on before sun heats it up, let it dwell for 5-10min, and rinse. May need to reapply.
Galvalume or galvanized has zinc in it and should not have this issue.
Youngandfree
Well-known member
I've seen it happen in pressure washing groups.
Youngandfree
Well-known member
Corrosive Chemicals & Substances in Contact with HDG Steel
*Updated 2024 What considerations are necessary when corrosive chemicals/substances will contact hot-dip galvanized steel? The AGA has published multiple…
My point was the zinc in the galvalume should prevent algae build up. I wasn't commenting on the use of bleach.Corrosive Chemicals & Substances in Contact with HDG Steel
*Updated 2024 What considerations are necessary when corrosive chemicals/substances will contact hot-dip galvanized steel? The AGA has published multiple…galvanizeit.org
Youngandfree
Well-known member
I've seen a ton of them get it. Fairly common.
marinusdees
Well-known member
My house had a cedar shake roof when I moved in in 1970. The local hardware was selling 1" wide rolls of zinc strips. I put them at the peak. Killed the moss for about 10" below the peak. The zinc washes only a sort distance at an effective level. My buddy who is superintendent for the largest commercial roofer in Washington (they don't do residential) is the person who told me about Tide+bleach. 25 or so years ago. I tried a number of thing before that. I now have a composition roof, still use Tide. Moss is the problem where I live.Central Florida, metal garage with stuff growing on some areas of the roof. Doesn't seem to care if it's in sun or shade. No tree over the patch in this picture. What is it and how do I get rid of it?
Youngandfree
Well-known member
Pump sprayer. Or build a bucket sprayer like this. El cheapo 1.2gpm water pump, battery adapter, spray wand, and some hose. 
Youngandfree
Well-known member
Not a whole lot with proper footwear.
Ahh, but to be young and free…(just kidding)
What is proper footwear for a soapy, smooth steel roof?
Youngandfree
Well-known member
Roofer boots with magnets in the sole sure make things easier. I've heard of guys wearing no slip deck boots on metal roof also.
marinusdees
Well-known member
You must have some brown guys (Hispanics). Typically they hang around Home Depot, looking for work. Show a little Gj resourcefulness. Wages are typically negotiable.
Don't cut your toenails for a few months?
Everyone has a different level of risk they're willing to accept. For me, the proper footwear would be whatever I had on while operating the lift I rented. I'm conflicted because in true GJ form, I want to do this myself, but I'm also a cheapskate cost sensitive. So I'm trying to figure out how to do it from the ground.
Youngandfree
Well-known member
Put a ladder against the eave is the easiest. Clean the gutters while you're up there.
I have no-slip deck boots and I would not walk with them on a soapy roof. Bad enough on a soapy deck...
In any event, walking on most any roof can damage the roof and should generally be avoided.
Stand on the tractor.
Long handled brush, you can use a pipe for an extension.
Do it in the rain. You're in central Florida, in a couple months that will be an every day event, yes?
Big Bad Dad
Well-known member
I bought one of these Doca Poles for getting insecticide powder into carpenter bee holes high up in the barn. But you can attach different fixtures to it. Last time I used it with a push broom head to get leaves, twigs, and debris off of my metal garage roof. Lightweight and extends to 12 feet.
docadone.com
Docadone - High Reach Extension Poles and Acccessories
Whether you need to clean the interior or exterior of your home, auto, or RV- we have everything you need to eliminate ladders and get the job easily done
docadone.com
welder4956
Well-known member
I used a 1 gallon pump sprayer set to spray a stream when I cleaned the second floor window trim. It was about 20 ft up to the top of the windows and I could easily have done the soffit about 2 ft higher. You should be able to get good coverage on your roof with a pump sprayer. Be sure to wear safety glasses or goggles to protect your eyes.
Sigh... More fodder for the "Have you ever bought tools..." thread.I bought one of these Doca Poles for getting insecticide powder into carpenter bee holes high up in the barn. But you can attach different fixtures to it. Last time I used it with a push broom head to get leaves, twigs, and debris off of my metal garage roof. Lightweight and extends to 12 feet.
Docadone - High Reach Extension Poles and Acccessories
Whether you need to clean the interior or exterior of your home, auto, or RV- we have everything you need to eliminate ladders and get the job easily done
Doug
Well-known member
I had the black streaks removed professionally from my asphalt-shingled house roof just last week. The stains were identified as an algae called 'gloeocapsa magma.'
The house is 42' long with a 5/12 pitch. The contractor had this weird looking sprayer nozzle that easily reached the peak from the ground. He give it two applications (and a rinse) and I watched the green stuff run out of my gutter outlets. It works almost immediately. The roof looks like new now.
He said the bleach he uses is several times stronger than what you'd get from the store.
The house is 42' long with a 5/12 pitch. The contractor had this weird looking sprayer nozzle that easily reached the peak from the ground. He give it two applications (and a rinse) and I watched the green stuff run out of my gutter outlets. It works almost immediately. The roof looks like new now.
He said the bleach he uses is several times stronger than what you'd get from the store.
