Mold Removal + Concrete

As you know, water or moisture can cause the most damage to buildings. Whether from a leaking roof or something as disastrous as a flood, water can be considered the root of all building problems. Water and moisture often lead to mold growth, sometimes in visible locations, but also in unseen locales throughout your building. One of the most important tasks after water damage is to remove all items from the building that have been touched by the water: sheetrock, insulation, rugs, furniture, everything.

Following the removal of flood water and then the removal of mud, we removed all items from the basement. It took days to remove all of the mud and over one week to get the basement to where it looked dry.  We washed our belongings, sanitized them, and have yet to return anything to the basement.

Now we are dealing with mold issues on the concrete basement walls, generally in locations at or below where the muddy water settled for a few hours. Originally we thought bleach would do the job, but it’s been a few rounds of bleach (one of those rounds was undiluted bleach!) and the white, fuzzy mold on the walls keeps appearing.

We have heard conflicting information, too. First, we heard that bleach would remove the mold and that the other products were all marketing. Then we heard otherwise. So, like a good homeowner and preservationist, I turned to my books and online resources. I learned that the chemicals in bleach are inactivated by organic compounds.

Darn. But, that explains why the white fuzzy mold keeps returning.

The concrete walls in our basement are certainly not of the non-porous variety. They are 83 years old and quite porous. In a handful of locations, I can see the aggregate that composes the concrete. It is not like today’s concrete, that’s for sure. Thus, the dirt and whatever else has migrated into my concrete walls is deactivating the bleach, and allowing the mold to grow.

We’re stumped.

All of the literature I have read, whether it’s from the National Trust or a university or any random website, simply talks about the importance of mold removal and safety precautions. The articles discuss the importance of drying out the basement and air circulation and a dehumidifier, of course. But, I need to know what to use in order to remove the mold and keep it away. I have yet to find a resource that mentions specific products proven to remove mold from concrete.

Can you offer a suggestion? What should we do?

I think our next step is to suit up and scrub the walls. But, with what? I’ll keep looking, but if you have an idea or even better – a proven solution – I would love to know.

Thank you!


19 thoughts on “Mold Removal + Concrete

  1. Frank says:

    And you’re sure it’s not efflorescence due to the moisture penetrating deeply into the concrete, dissolving the concrete salts into solution, bringing them to the surface, and then leaving the salts behind when the water evaporates? Sometimes masonry efflorescence can look a lot like mold, and your use of the terms “white” and “fuzzy” to describe it got me thinking.

  2. Luke says:

    Trisodium Phosphate is illegal to sell in Vermont, mainly because phosphates contribute to algae blooms in Lake Champlain. In Vermont they sell TSP-Substitute, in my experience it does not as work as well as the real thing (I’ve used it for cleaning siding and roofs). TSP is still sold in NH and you can probably be found online as well.

    At Gettysburg we use a product called D/2 Biological solution on the granite sculptures and marble headstones that tend to host biological growth (lichens mainly) it works fairly well. It is non toxic and biodegradable (user friendly) but fairly expensive. I’m not sure if it is recommended for mold but it might be worth some research.

  3. larry waldrop says:

    Hey, you should check out Nisus mold clean, it was made for wood but works well on concrete also. Nisus only sells to pest control companies but you can usually find their products online for sale from other companies.

  4. Kate Walsh / designhouse9 says:

    Hydrogen peroxide perhaps? It has removed mold from plastic for me but may not be as effective on concrete. Still, I thought I’d pass it on since you are researching. Best of luck. Sounds like a nasty problem you’ve got there. Another thought–are there any mold remediation companies in your area? They might be another source of info or solution.

  5. Tom Athey says:

    Are you a Los Angeles homeowner? If so, do you currently have a mold problem? Even if you don’t have a mold problem right now, there may come a time when your home develops one in the future. Although mold is often talked about in a negative way, it is something that many homeowners have to deal with. The problem is that many homeowners do not realize how serious mold can be. That is why many choose to not have their homes undergo a Los Angeles mold removal project, even when it needs it.

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