Black Mold On Concrete

[Loaded]

My balcony (concrete) is under the roof overhang and when it rains water drips onto it. There's a black mold spread over the surface that looks unattractive and seems to eat into the paint on the concrete. It's the same mold that covers most concrete buildings in this part of the world.

Any ideas how to dissolve/clean and how to prevent?

Cheers

[Lost in LOS]

mix bleach and water and spray and it will disappear

concrete sealer to prevent further

[Shrubbery]

You may be better off asking this question in the real estate forum. There are some helpful people there.

[onzestan]

mix bleach and water and spray and it will disappear

concrete sealer to prevent further

Concur, btw bleach is "haiter"in Thai.

cheers

onzestan

[JetsetBkk]

mix bleach and water and spray and it will disappear

concrete sealer to prevent further

Concur, btw bleach is "haiter"in Thai.

cheers

onzestan

Concur duay. Use the one for "whites" - contains about 6% chlorine.

[lazeeboy]

mix bleach and water and spray and it will disappear

concrete sealer to prevent further

Concur, btw bleach is "haiter"in Thai.

cheers

onzestan

Concur duay. Use the one for "whites" - contains about 6% chlorine.

scrubbing brush and a little elbow grease should do the trick

[ProThaiExpat]

I have a serrated concrete driveway that got black, as did the approaches and the street in general. I used my high pressure water sprayer and it took it all off. Driveway looked new again when I finished.

Will have to do it again though, it is good for about a year. The soot from spring burning probably adds to the problem.

[MrSquigle]

Exactly....try to give the environment a little break...more chemiclas into the drains to empty into the sea...specially when a hard scrub with hot water will do the same job.......ahhh bugger it, not like the klongs are a pristine environment to protect, go for it and double up on the bleach.

[Scott]

Yes, give the environment a break, don't heat water!

I have the same problem, I just let it be, it helps keep the neighbors thinking badly about farangs!

Actually, I will follow this thread in the event that I find an easy way to clean it up. It actually does bother me. I tried brushing mine and I ended up with a gooey mess. When it rained again, everything got black!

[Grover]

hydrochloric acid, quick, easy, and ends up very white.

it gets rid of everything on concrete, easily does oil stains and mold. I put some on a driveway oil stain once, got rid of the oil but now I ended up with a white patch instead of a black one

Edited October 23, 2007 by Grover

[cdnvic]

All good ideas. Just bear in mind the balconies, clothes lines, cars, and pedestrians under you (if any) when using chemicals.

[percy2]

mix bleach and water and spray and it will disappear

concrete sealer to prevent further

Concur, btw bleach is "haiter"in Thai.

cheers

onzestan

Correct.

But like "Fab" for detergent "Haiter" is a brand name.

Cheers

[my friend I]

Vinegar

[naka]

Exactly....try to give the environment a little break...more chemiclas into the drains to empty into the sea...specially when a hard scrub with hot water will do the same job.......ahhh bugger it, not like the klongs are a pristine environment to protect, go for it and double up on the bleach.

Agreed Mr.S ... plenty of my old unrecoverable jocks go floating down the klong !

Naka.

[Tony Clifton]

Clean it ONCE.

Let dry.

Apply an epoxy style paint mixed with a bit of fine sand to avoid slipping when wet.

Never clean it again.

Watch out for dripping onto people and stuff under.

[Loaded]

appreciate the answers- thanks gents.

I'll experiment with the bleach idea first. Bit worried as the run off from the balcony goes on to red roof tiles just above the front door. I've scrubbed with soap and water before but the paint is starting to flake.

[JetsetBkk]

hydrochloric acid, quick, easy, and ends up very white.

it gets rid of everything on concrete, easily does oil stains and mold. I put some on a driveway oil stain once, got rid of the oil but now I ended up with a white patch instead of a black one

Hmm, I might give white "Vixol" bathroom cleaner a try - 20% HCl. My concrete drive is very dark now so I will try the cleaner (diluted) and plastic broom to scrub it. Have to wait for the rain to stop first though.

[cdnvic]

appreciate the answers- thanks gents.

I'll experiment with the bleach idea first. Bit worried as the run off from the balcony goes on to red roof tiles just above the front door. I've scrubbed with soap and water before but the paint is starting to flake.

Just get a spray bottle and mist the bleach/water mix on. Apply it several times and let it sit for awhile.

[Grover]

just be careful with these chemicals, with the HCl wash your skin immediately if you get in on you, especially at 20% concentration, wear gloves and careful not to get in on your clothes or eyes. It will lose its potency if you dilute it too much though. 20% is a good concentration I think. Dont worry about the fizz, it looks evil but its normal.

with the mist bleach, careful not to breath the fumes/mist or get it in your eyes as its a toxin.

[qualtrough]

You can buy a brass brush with a long handle for under 100 B in hardware stores. I used that to clean black algae growing on my red brick walkway. Scrubbed them up nicely like new. As for treatment, go to a Homepro store and check out Thompson's Waterseal products.

[dominique355]

Great tips for removing the black stuff, thanks all.

What might help prevent it from coming back is to install a gutter. Most Thai houses have no gutter so that the rain water just pours down on anything below.

About the high power water jet, such as Kaercher, does someone know what model is good? I need to clean my drive way.

[tgeezer]

Great tips for removing the black stuff, thanks all.

What might help prevent it from coming back is to install a gutter. Most Thai houses have no gutter so that the rain water just pours down on anything below.

About the high power water jet, such as Kaercher, does someone know what model is good? I need to clean my drive way.

Are you sure it is mould? I go away for six months and the red terra cotta tiles on my roof garden go absoultely black when water accumulates and evaporates leaving the soot behind. (This is Bangkok problem in case anyone thinks we are in the wrong forum. I used to have planes overflying from the old airport and it was worse) I can soak it and then brush but it will take months ti la nit ti la noy and If I was here I would try to rinse the roof with freshers often if it has rained. You may be in a position to do this next year.

[stateman]

I'll experiment with the bleach idea first. Bit worried as the run off from the balcony goes on to red roof tiles just above the front door. I've scrubbed with soap and water before but the paint is starting to flake.

How about putting a piece or cardboard (tape it down if need to) or somthing to catch the runoff. Toss the cardboard afterward.

[stateman]

Clean it ONCE.

Let dry.

Apply an epoxy style paint mixed with a bit of fine sand to avoid slipping when wet.

Never clean it again.

Watch out for dripping onto people and stuff under.

bleach works wonder.

On the subject of bleach going into the sea, etc. I can say from my experience when I took care of my swimming pool, for which I had to keep measuring the bleach/chlorine ph. I found that in a short few days it lost a lot of its concentration. So I think for a small quantity under discussion here, given its breakdown effect shortly, I'd think it should be OK. Some chemist may comment about this.

Then on sealing.. In the US, they sell packets of somthing to prevent mold from growing. Very inexpensive.. like about $1 a packet (sorry don't remember the weight). I was told that expensive paints already have these mixed in. For inexpensive paint we are supposed to mix this in the prevent the ugly black mold you often see. I wonder if you can add this to the sealant before applying to concrete.

Just a thought.

[chownah]

Throw your compost onto the mold and toss on some grass seeds....in about a year it will be a lawn and all you will have to do is mow it!!!!

[elkangorito]

I quickly glanced through the comments. I saw that someone mentioned vinegar...a great choice.

Many current commercial products for removing concrete stains are now based on ascorbic acid (fruit juice).

[percy2]

I quickly glanced through the comments. I saw that someone mentioned vinegar...a great choice.

Many current commercial products for removing concrete stains are now based on ascorbic acid (fruit juice).

Most people refer to ascorbic acid (though not completely correctly) as Vitamin C.

Cheers

[Crossy]

Throw your compost onto the mold and toss on some grass seeds....in about a year it will be a lawn and all you will have to do is mow it!!!!

If you get some ducks and geese you won't have to mow it either, decorative and functional (you can eat the eggs too )

You will however have to remove goose turds

[wineaux]

will these solutions also work for stains on sandwash?

[raro]

got a similar problem in the bedroom for a week now after the heavy rains we had recently. We have the windows open for a couple of hours in daytime and use aircon which also dries up the air at night, so the bedroom has good air circulation.

Used to have this before in another house I lived in. The maid cleaned the walls several times but it always came back.

I suspect the mould sits inside the wall and what we see is only the tip of the iceberg. Any idea how to remove the cause and not only the symptoms? Is bleach with water enough?