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treatment for black mold/damp smell on bricks?


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Does anyone know how to treat black mold on bricks? They have just been power cleaned and I understand there may be a "product" that can be sprayed on them to prevent the mold from reoccurring.  These bricks are surrounding a swimming pool so they are often damp and they get very black and smelly - particularly in the shady side of the yard.

Thank you

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I use a diluted bleach in either a garden sprayer or hand held spray bottle. When going after what grew during a rainy period a brushing of the area to help bust the surface of the mold helps the bleach do it's thing. Sometimes leaving the bleach on after it appears dry gets even better results making the mold disappear. It grows over a period of time so treatments sometimes aren't a rush job so taking days of lazily working it. If you want it gone in one work period a brush and bleach diluted or not is the way I go. One thing about concrete is it seems bleach can have an effect on it so rinsing helps prevent deteriorating the concrete. The bleach doesn't do the grass and worms in the soil any good so best to go light and wait till the bleach has done its thing.

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You might try taking a picture and showing it to a gardening specialist, nursery or pool specialist. There is black algae that grows on areas that get wet even with sunshine during the day and it keeps building up. A garden supply store or pool maintenance store with a lot of fancy stuff could have stuff like you are looking for. A concrete pouring businesses is another place to ask.

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We remove it with wire brushes that do not damage as much as the karsher but then it has to be done every season.. I am going to ask what they do in France and get the name of the product. I would think that people who live in the Mobile , New Orleans area would know as well as they have the same problem.

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Thanks everyone -  I appreciate the insights.  I discussed the bleaching option with my gardener. He has power sprayed all the bricks to remove the black mold and now he is going to try a bleach/water solution.  He also mentioned Muriatic acid/water solution  -  I am not keen to use anything toxic but apparently this is safe. We are going to test both out  -  I will post with results. 

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12 hours ago, feewee said:

Thanks everyone -  I appreciate the insights.  I discussed the bleaching option with my gardener. He has power sprayed all the bricks to remove the black mold and now he is going to try a bleach/water solution.  He also mentioned Muriatic acid/water solution  -  I am not keen to use anything toxic but apparently this is safe. We are going to test both out  -  I will post with results. 

That type of acid eats some sorts of plastic and definitely concrete and plaster. It's good for taking mineralization off pool plaster when drained but you have to ph up the wash off with a baking soda type of stuff so it doesn't eat drainpipes downstream of the wash off and that's even in diluted form as a washed off solution. Muriatic acid is a diluted hydrochloric acid. Although it will eat the brick and concrete and mortar taking the mold or algae with it. I'd go liquid pool chlorine that's much stronger that store bleach you'd normally consider chlorine but it just isn't as strong as the pool chlorine in gallon jugs. Stuff is strong. I noticed pressure washing getting up cllose with the nozzle tears up concrete hehehe oops then it can even drive the black stuff deeper into concrete pores. Hard to win sometimes.

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11 hours ago, mudgirl said:

A regular stiff scrub brush and bleach solution works fine and doesn't damage the bricks at all. Wire brushes and powerwashers are not necessary and don't work nearly as well.

Yep. going after algae every year or when rains cause it to build they'll just trash the brick. I'm currently using a short handled car tire scrubber. Doesn't damage anything. Just rinse when you think it should of had effect so you can see if any stuff is still sticking. Worth taking a break to let the chlorine do its thing since a little remaining stuff will of disappeared from residual chlorine by time you finish watching the world go by for 10 minutes or so. The brush busts the surface of the black algae so clorox can get in then and finish it off.

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One thing I found out through experience is never to use that 5-1 sealer (the stuff that smells like Elmer's glue) on outside stuff where mold builds up. Mold loves to grow on that product. Years ago I had used it on my tile and cement walkway, but only did a small portion of it, as I ran out of the sealer. The area where I had put that sealer grew lots of black mold, and the rest of the walkway didn't.

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  • 2 weeks later...

UPDATE: 

We sprayed with power washer (just water) before I posted for advice.  I agree this has the risk of breaking down the bricks - some weren't in great condition to begin with but I can see where good bricks are now pitted.  Suggest going easy on power washer -  if you can turn down the dial or use a less powerful alternative.  A long handled stiff or wire yard brush might have been handy but I couldn't find one in local shop. Stiff scrub brush (handheld) -  used it on small test area and it worked ok but the elbow grease required to do whole pool area and patio was just too overwhelming and Gardener would probably quit!

We followed up with diluted bleach (chose to forego the muriatic acid solution based on the above advice from Stream) and it did seem to soak into the bricks and so far they remain fairly clean and less moldy (some are good, some are still blackish but in a less dramatic way). The areas in the shade took days to dry out but now that they are dry they look better.  The best part is that the acrid moldy smell has dissipated (although I can still catch a whiff from time to time ). Getting rid of the smell was the reason for all this effort in the first place.

I can see that this is not a "one and done" kind of chore but will need to be added to the growing list of regular maintenance post rainy season...just a reality of life in this area.  I also think staying on top of it as one poster remarked is a good idea.

Thanks all for your help, everyone!  

 

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46 minutes ago, feewee said:

will need to be added to the growing list of regular maintenance post rainy season

Actually, you should clean them before the rainy season- mold grows on organic material, i.e. dirt. So without going on a big bleach cleaning chore, just hosing them down on a regular basis will help keep the mold from wantting  to grow there. And give them a bleach scrub halfway through the rainy season.

It's much less work if you never let it build up badly to start with. 

And when using a powerwasher, do not aim the spray directly at what you are cleaning. Use the widest spray setting, and spray at an angle, more from the side than the top. Not only will it lessen the scoring of the brick, it does a better, quicker job of "lifting" the black mold off.

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I have removed 100s of acres of moss, algae, mold and insects from historic buildings. The tool of choice is a super heated steam cleaner. I have a consumer level steamer here, which would do the job, and are not expensive. There is a local company offering steam cleaning.

The steam " cooks" the organic matter and bugs. Most importantly, this goes down to the roots and kills them. Chlorine just makes the organic matter white, you have come every year because like a grass lawn, it will just grow back. There are two reasons pressure washers should not be used. The first is that weakens or destroys the grout more than the brick. Repointing the mortar, using a professional Mason, and project specific grouts, is not inexpensive. The second is that it creates a big mess. In Vancouver, where I was from, all water and detergents have to be removed from the jobsite. The steam cleaning works up to three years versus an annual haircut.

One tip I can give you is go to a local vet or agricultural store and buy a jar of horse shampoo, containing Laural Sulfate. This is a wetting agent, not a detergent, it loosens the crud, making it easier to remove. It is used for horses because it cleans out the dirt, not the oils. This way the horse does not have frizzy hair. A lot of humans use the 'mane and tail ' cleaners on their own hair, for a nice shiny coat.😊😊

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Thanks Chilin  -  steaming sounds promising  -  do you know if there is anyone in the lakeside area that provides this service?  If not, I am not opposed to buying a steamer but not entirely sure what it is. I use a steam cleaner on my tiled floors up north -  same thing? 

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They seem to be only on Facebook. 

https://m.facebook.com/ajijicsteamclean/

I think you are describing a steam mop. The trouble here is that the cleaning ladies are afraid of these newfangled gadgets. They are excellent if you have pets because they get itchy and swollen paws from some of the floor soaps we use here.

If you search "vapor cleaners" that will get you lots of hits in the U.S. and Mexico.

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