Mold Removal and Disinfectants

The CDC has a pretty good sectionof advice on cleaning and preventing mold. I don't know if you ran across that one in your searching, if not check it out. Keep in mind some molds are pretty nasty to humans. Yes - you want to remove the mold. Straight bleach does a better job but is also much more hazardous to you and the area. Check out the CDC site, search on mold removal for those ideas. Hey, maybe your squirrels will eat the mold since they can't get to your solar cables now! Just kidding, sorry for the bad joke.

No problem Matt. I needed a little comic relief. It seems like everything comes at once. In the last month I've had the solar squirrel problem, my HVAC broke, I have a roof leak, my dog was poisoned with rat poison, and the access road to my subdivision was flooded, with 2' of water at one point, for the last week. That's a good idea to look at the CDC site. I should have thought of that; maybe all that mold is affecting my mind.

Thanks, and Merry Christmas.

Don

Wow you have had a bunch of things to deal with. Hang in there. I hope you have a great Christmas too and that the New Year brings less "events" at your place.

Whatever you use, just remember enough chlorine gas can be deadly and also reactive to some things so be very careful!!

I was removing the reflective aluminum coating from a parabolic mirror and while there are better acids suited to this process, the only thing at hand was muriatic acid from a Home Center.

I cast about for a plastic tub to bring outside for the stripping process but couldn't find one. The grounds superintendent told me not to bother as they use muriatic acid to bleach stains in the cement anyway and to remove stubborn moss from the shaded areas

I'm not a biologist but my limited knowledge suggests that muriatic acid may prove more effective in destroying mold spores than any of the chemistry you've tried thus far. To date the plastic has not shown any reaction but the metal in the drain did.

Extended exposure to the fumes from muriatic acid should be prevented. When I use it in my bathroom, I make it a point to pour it where it's needed and leave the room immediately, closing the door behind me for a few hours.

L.J.

L.J.,

The CDC web site recommends using a mild solution of soap or detergent to clean mold. I think the muriatic acid would work but it's pretty strong stuff unless diluted. If you are using a strong concentration you may find that the vapors will oxidize (rust) metal parts in the area. That happened when floor installers used muriatic acid to clean grout they left on my tiled floor surface. All of the door hinges in the bathroom rusted. I think one reason that vinegar (acetic acid) is recommended by some is that vinegar is a very weak concentration of acetic acid.

Thanks,

Don

Hi Don!

What you wrote is accurate Don and consistent with what I wrote about the effects on the metal drain.

When forced to use something more aggressive, like muriatic acid, I now either dilute it, as you suggested, or build a damn around the drain using glazing putty.or a modeling clay (Plasticine). I've not tried it yet, but another suggested a damn of silicone which when cured can be easily pulled free from the shower floor.

Have a nice Holiday

L.J.

I have found a strong solution of Hydrogen Peroxide works very well and I am very sensitive to mildew. 3% you can try for a start but you may need to go stronger such as the grade that hairdressers use. Anything above 3% you must use care with since it is very strong. Health food stores have 35% and you can dilute to what ever works and spray it on being very generous. HAZMAT training is recommended for the strong solutions.

Roy,

I hadn't thought of hydrogen peroxide. As a retired firefighter and HAZMAT responder, although I haven't dealt with mold in that capacity, I can tell you that you are correct about having to be careful about using the stronger concentrations of hydrogen peroxide. HP is a strong oxidizer (that's why it works so well) and, at high concentrations, can initiate combustion when in contact with combustibles such as wood. I think I will still have to remove my shower pan though, because there are some areas that I just can't access----hidden compartments underneath. The pan is constructed in a honeycomb fashion for structural stability. After I remove the shower stall and pan I think I will treat all of the remaining wood bottom plates and studs with a detergent solution as the CDC recommended and then treat everything with HP.

Thanks for your input.

Don

Even at 35% you do not have to worry about the combustion factor but it should be kept cool. I would not waste my time on detergent you have to kill the spores and the safest is for sure the H202. If you fog it in with air you should get most areas since it will creep quite a distance. I have had 100% success with it in many areas including wood soaked. I cannot stay in a building with mildew for even a short length of time. For fogging you can use an air operated undercoat gun or similar you may even be able to rent same. Good luck.

While sometimes it simply takes what it takes and costs what it costs, I hate it you might have to pull the entire stall and all out.

It crossed my mind that to get whatever the best mold killer chemical at difficult places to access it might be possible to rig a plastic detergent bottle with a plastic tube and squirt stuff into the difficult to reach areas otherwise.

(When I was a kid we didn't have money for real squirt guns and dishwashing bottles were very powerful in the role.)

Who knows even if to scrape and wipe away the mold there is required, maybe some holes in the shower stall with plugs would allow that sort of rig to be used for periodic preventative treatments in the future.

Seems like some environments have some endemic molds around for I had to go back every so often and spray diluted chlorine onto the walls of a painted garage to knock back mold that kept coming back.

It was in a wooded area near a creek.

I think Kilz Primer is supposed to inhibit molds and if you have to go to the trouble of tearing everything out and putting it all back, painting with that may be preventative. Who knows, maybe if you do have to take everything apart and put it all back together, just in case, salt back there would be of aid.

Don,

I think there is a bit of overhype about molds, but can you put an ultraviolet light on it for awhile (overnight)? but beyond that, if you solve the leak and the area is relatively dry afterwards, I doubt any further growth of the mold will take place.

I have lived in houses that were exceedingly damp and know full well what a problem like mold can be. But I doubt it will secretly grow into some mass that will get loose and destroy your neighborhood.

If you have a basement below this area is it worth cutting a hole to allow air flow and help keep the area dry?

Good luck and Merry Christmas.

Thom.

Thom,

Initially I didn't know what was going on. I started out with a sinus infection but it persisted for another couple of weeks. Then I found the mold. I actually had to take out about 12 sq. ft. of wood flooring next to the shower. My house is on a concrete slab so I can't access the shower from underneath. According to the EPA, even dead mold spores can still pose a health problem although I guess if I sealed everything up the spores wouldn't have anywhere to go if I cure the moisture problem.

Merry Christmas.

Don

Don,

I've had a problem with black mold in condensation areas around the windows. It can be cleaned off with soapy water but returns at the first hint of moisture. I experimented with a few treatments and the one that worked is to put a dash of juniper essential oil in your soapy water. Not only it made it much easier to remove the mold completely, but in areas kept dry the mold does not return. Juniper is strongly antifungal, and the residue that penetrates and protects the wood is not harmful.

But if you are trying to disinfect a concrete slab, that's a different matter. I suspect that, after cleaning and removing all mold and moisture, an anti-fungal paint job is probably your best bet to prevent mold from returning. A bare concrete surface is dusty and it's too easy for spores to hide in that dust. Paint will help - make sure it is interior rated to avoid any allergic reactions to the paint itself.

Hope this will be the end of your run of bad luck! Merry xmas.

Thanks again to everyone for your comments. I have a lot to consider. The UV light is another consideration. During my HVAC repair, the technician recommended installing a UV light in the the HVAC to kill any mold spores in the damp area of the HVAC, I think by the A-coil. Evidently, mold growth in the HVAC is not unusual. I just don't know if it is a problem of such magnitude that needs addressing. My wife is sensitive to mold and I believe that the recent mold problem caused my sinus infection. However, I checked the EPA website and the EPA says that the type of UV lights typically installed in HVAC's don't kill all of the mold spores. Are there different types/energy level UV lights that will perform more effectively for use in my shower and HVAC?

I hope everyone had a good Christmas.

Don

had dinner at a friends house and I met a person who made Ozone generators just for odour removal. industrial/ commercial i believe. if you do your house, I think you have to leave the premises for 2 days. Ozone is the strongest oxidizer, then hydrogen peroxide, then chlorine bleach. I have removed mould and mildew from several houses and originally the senior person preferred bleach. nearly killed us even with fans. I would see if you can rent a commercial ozone generator and also spray H2o2. wipe up surplus liquid. if it [odour/mildew is persistent, sounds like you have already tried, there may be mildew in / on drywall, plaster, vapour barriers, fibreglas insulation, heating ducts, wood and odour even in concrete.

ozone will fade curtains, rugs, paint etc. keep that bath fan on after showers.

I cut out the fiberglass shower stall. Good thing; there was mold in inaccessible areas on the underside. I vacuumed the concrete and wood studs under and around the stall, brushed everything, vacuumed again, and sprayed everything with detergent and let it air dry. I no longer smell the mold. It has been about a week. The only evidence that I can see is some black color on a couple of wood framing members. Is it possible that the black is just residual staining from the mold, or mold "imbedded" in the wood? Sometimes we forget, but most times we turn on the bath exhaust fan before showering and leave it on for at least 10 minutes after.

Thanks,

Don

If the area is still accessible I would still spray it down with Hydrogen Peroxide. You can get away with the 3 % drugstore stuff and be generous. Works great and gets into all areas and wood grain. Not dangerous at this %.

Remove all evidence of stain, cut it out for sure you don't want to do this again soon.

I find it more effective to open the bathroom door especially in winter the humidity is favorable when widely dispersed.

sorry took so long. missed your reply. It is both permanent stain and i'm sure some active mildew spores. we usually take out any wood that has been water logged, even if it is not contaminated with mildew. It is quite often soft. I understand it is necessary to meet code requirements.

Pretzyl, bwire, roy,

Thanks for the info. The black stain I told you about is on some of the studs but mostly on the pressure treated bottom plates. I can sand, shave, chisel the wood off of the studs to get to unaffected wood. However, the bottom plate is another story. When I originally discovered the problem it was because I saw water staining on the outside concrete slab. So, I'm sure that water and mold got underneath the 2X4 bottom plate. Is that going to pose a problem if I don't replace the plate? I can force H2O2 under the plate with a garden sprayer or make a dam along the plate, fill the area with H2O2 and let it soak into the plate.

I sometimes wonder if I should go back to an outside shower, which I used when we were building our previous house!

Thanks again,

Don

Replace the plate, it's not so much ordeal get the sawzall cut the nails an git'r done, get it all out.

I have some very effective mold control products and in the fine print you always find repeat when the mold returns

the plate has got to come out. the plates we have taken out had leaf like patterns of fungus/mold on the bottoms. when we remove a plate in sections, we check for water damage and fungus mold on the removed wood. keep chopping out [small pieces at a time] until 2 feet past end of contamination. while portions of the plate come out you can check for water damage and or fungal/ mold infection in the studs at the same time.

support can be made from 2 x 4's 2 inches longer than floor to ceiling height. place in strong position on ceiling and jam bottom towards plate. it can take a lot of load. use enough to carry load temporarily.

to take the plate out in small pieces, 6 inches from a stud, cut through the plate just about to the floor. make another cut 4 or 5 inches towards the stud. take this piece out. make another cut on the other side of the stud. use an old wood chisel or a nail bar and split the plate down the grain towards the stud. say 1/4 to 1/3 rd of the thickness. there are nails coming down from the stud. or there should be.

this way you are only splitting a small amount of wood at a time and when the wood is clear of the nails you can hacksaw 1/2 way through the nails and snap off. inspect and determine how much rust these nails have endured. at this time you can determine the condition of the bottom of the exposed stud bottom.

If you have one rotten stud bottom, I will tell you what we did once. in a carport, repaired and seismic upgrade. we cut off the lower 1 1/2 inch of the stud. this removed all rot and stain. we placed another plate from beside left neighbouring stud across to beside far right neighbouring stud. about 32 inches double thick plate under one stud.

is this is a supporting wall or a privacy wall? you don't want to do this for another 25 years at least.maybe with a knife cut a sliver off the bottom 4 inches of the stud 1/4 inch thick. you will be able to see if the dark stain is surface/superficial or through and through. you should be able to determine if this is fungal - bacterial infected or water logged for too long a time. wood cells easily crumbled/splintered apart. or if you have a sliver of wood which does not crumble easy or does not compress easily between the fingers when pinched hard it probably is all right. check for odour also.

then sweep, sterilize, rinse, dry and repeat if necessary.[joke]

if half is removed and there is still more damage, then replace half of the plate at a time. unless you have some safe way of supporting the entire wall while the whole plate is removed.

try to remove any dust, sawdust left behind on walls, floors. it retains moisture if it ever does invade and is future food for decay and mold/ bacteria.

don't use your household vacuum cleaner unless it is easy to disassemble and sterilize entirely. [we have a dedicated shop vac with a 50 foot exhaust extension hose to the outside for when we drill, saw, grind contaminated areas]. you could easily be spreading mold spores, bacteria into your house later. some fungus spores -and bacteria are extremely serious hazard to health when ingested airborne. [gone aerosol] wear respirator with HEPA filter when cutting. the ones that look like paper and certified for hazard dusts are adequate also. hope this helps out.

bwire and pretzyl,

Thanks for the detailed response. I didn't mean to sound like a crybaby about having to remove the bottom plate. I guess I knew the answer before I asked! The walls are supporting walls. The largest contaminated part is where the side walls meet the exterior walls so there are two corner "T's" 48" apart where the shower stall was. I've seen the 2X4 temporary supports used sveral times and I used that method several years ago to support a carport while I was inserting columns. Now I just have to find out EXACTLY how the wife wants it rebuilt since we may be moving things around.

Thanks again,

Don