Contractor Talk - Professional Construction and Remodeling Forum banner

mold in grout

6K views 58 replies 17 participants last post by  MarcoPollo 
#1 ·
had our bathroom remodeled about 5 years ago.

tile guy did a beautiful job. noticed today though on the grout where the tile meets the tub, there is what i am assuming mold (grout is black) for about 3/4" long. no where else.

other than hire him to come back, grind it out and regrout that, are there any chemicals worth trying that would remove that black spot in the grout?
 
#3 ·
No bleach, it's more dangerous than the mold, it only works on hard surfaces and is made up of mostly water, which mold loves. While it will clean up the discoloration it's not the best for actually killing it, especially in a porous surface like grout. There are plenty of non caustic, non hazardous solutions. You can find them at pretty much any hardware store.

Also, keep in mind the mold my be coming from behind the tile. Check for any cracks in the grout above the molding area.
 
#8 ·
It doesn't like basic environments, so anything with a high PH works in your favour, baking soda, oxyclean, chlorine etc.

I know Mike Holmes rants and raves about how dangerous it is, but we still put it in the water we drink, the pools kids swim in and the dishes we eat off.
 
#9 ·
Facts are facts. Even the EPA and OSHA have removed bleach clean up on all but hard non porous surfaces.

This has nothing to do with what any one individual thinks. It's just not effective on anything other than hard non porous surfaces for killing mold.

Yes it is used to disinfect water, but in controlled environments and with great care. It's not splashed about with little to no respect to is danger.

It's is highly caustic and reactive. Not smart to use near ammonia products which are often used in bathrooms. It will discolor carpet, wood and other materials and is a skin irritant.

Why use it when there are much more effective products that are not nearly had harmful?
 
#22 ·
update..

this is why ditch diggers should stay away from mold/grout issues.

i'm scrubbing away...NOTHING happening.

wife comes in and says..."you know there is a thin bead of clear silicone over that grout, don't you? now that i think of it, for grout, it did feel mighty smooth.

i'm calling the tile guy, have him come take care of it. if i try and recaulk, i'll use a whole tube, and it'll look like chit.
 
#28 · (Edited)
If it is behind the silicone, and not on the surface, it's coming from behind and wicking forward... which would indicate a potential bigger problem that you are just starting to see (or it could be something you caught in time)... you mentioned in an earlier post that he used cement board, what type of water-proofing did he use on the walls prior to tiling and did he seal the seams and fasteners before doing so?

If there was no water proofing applied, and he was relying on the cement board as the barrier, the news may not be good as cement is porous...

One of the ways to increase the longevity of a tiled shower, is to get in the habit of squeegeeing the water off the walls after each use (literally takes 10-15 seconds)... most water evaporates naturally through the course of the day, but leaving as little water to do so increases the life of the shower...

Another question to ask is what type of grout was used... cement or epoxy, sanded/non-sanded... corners should be caulked not grouted... one of the reasons why is water follows the path of least resistance and can be absorbed into cracks in the corner and at areas where water has a tendency to pool (where horizontal and vertical surfaces meet)...

.
 
#23 ·
IMO, why is there silicone over the grout? Did you do it, or the tile installer?

Then if the grout has silicone over it,and it has mold, the issue is deeper/inside than the surface of the bathroom!

You may have a water issue behind the tile, that will need to be addressed here.

Remember one thing , EVERY house/home, has mold or the mold spores in it, just takes bit of moisture, and little heat to grow!
 
#25 ·
IMO, why is there silicone over the grout? Did you do it, or the tile installer?
we didn't do it, must have been tile installer. i know when he did it, there was like a cement board he put up behind the tile. locally, he's known as the "guy that does it best". he does tile work on most of the upscale homes here.

dunno, i'll have to ask him what's going on.
 
#27 ·
No matter what cleaner you use, it'll come back. Chances are your tile substrate is wet which will harbor the growth in the future...that is if he tiled directly over the CBU without topical waterproofing.

Best to keep grout in order and sealed with a quality product. Clean regularly, squeegee when done and ventilate the bathroom.

Oxygen bleaches are a welcome improvement over the chlorine variety cleaners on the market.
 
#31 ·
The silicone caulk sealed the grout at that spot. If the chosen grout is porous then water can be trapped behind the grout there.But since it is only at one spot, check the grout and be sure there isn't a gap or missing grout near that spot.. Also, when he originally applied the caulk, he may have left a small space where water could enter behind the caulk.
 
#32 ·
Chlorine bleach performs a good and safe job, viz-a-viz mold cleaning. However, it does a lousy job viz-a-viz mold remediation.

Bleach will only kill mold with which it comes into contact. In other words, it kills the surface but not the root/spore.

Concrobium (sp?) is a product that we have used with great effect. It (supposedly) kills the mold ... all of the mold.

Used the stuff in foggers for large area treatment. However, simply applying it to the surface, in instances that there is little mold, works quite well. Kills the stuff all of the way.

There are other products out there that do as good (or to believe their marketing) better job. However, the majority of my experience is with Concrobium.

All kinds of stuff on the world wide interweb ... look it up.

Try the bleach first. If it comes back go for another product that will effectively kill it.
 
#33 · (Edited)
Chlorine is far from good to clean and kill mold in grout and it's far from safe. It's in the same class as gasoline. It's caustic and highly reactive to other chemicals. It also leave a hazardous residue.

Bleach will not kill the mold in the grout. It even states that it's only effective on non porous surfaces.
 
#44 ·
Mold Armor is a very popular choice and claims to work on hard, as well as porous materials. It's main ingredient is Sodium Hypochlorite. When I read Clorox's safety data sheet, there's the same mention of chemical.

I'm not a full believer that standard household bleach doesn't absorb and kill mold/mildew beyond the surface of porous materials.

http://www.homedepot.com/catalog/pdfImages/89/89b9c3e0-e9dc-4fa4-bdde-708a2cacaf28.pdf

https://www.thecloroxcompany.com/downloads/msds/bleach/cloroxgermicidalbleach1jw2014-08-24.pdf
 
#48 ·
I am of the opinion, that at some point in time, no matter what the substrate, or the sealer, or the superior workmanship in the install process, its a matter of "when" mold occurs, not the "if".

And whether you just eliminate the cosmetic effects, or "kill it", its going to come back again. If not the same spot, then a new one.

No grout lasts forever, no caulk lasts forever, no two materials once joined together will forever maintain an impermeable surface.

What amazes me, is when I/we have done tear outs in really old - I mean 1900 era houses with tile work not much different than the Romans used - how little hidden mold there is.

Old tarpaper and asphalt and lead sheeting.
 
#50 ·
If you remove as much of the food and environment they thrive in, invasive mold and mildew shouldn't really ever be an issue, especially with regular cleaning and good ventilation.

We try to install showers and tubs with mold and mildew in mind.

1) Ventilation in the wet area itself controlled by a timer. Educating our customers on running it 20 minutes after the shower or bath is complete.

2) Kerdi board and Durock as our main substrates (both do not provide a hospitable environment).

3) Try to stay away from porous stone (travertine)

4) Urethane or Epoxy, both of which are not porous.

5) Moved away from grout caulks and towards mildewcide caulks.

So far so good.
 
#57 ·
If you remove as much of the food and environment they thrive in, invasive mold and mildew shouldn't really ever be an issue, especially with regular cleaning and good ventilation.

We try to install showers and tubs with mold and mildew in mind.

1) Ventilation in the wet area itself controlled by a timer. Educating our customers on running it 20 minutes after the shower or bath is complete.

2) Kerdi board and Durock as our main substrates (both do not provide a hospitable environment).

3) Try to stay away from porous stone (travertine)

4) Urethane or Epoxy, both of which are not porous.

5) Moved away from grout caulks and towards mildewcide caulks.

So far so good.
That reads good enough to put right into the warranty/service document. It is clear and states why you do what you do objectively.

One of the hardest things to do, is put in writing what the client must do to maintain the finished job and stay within warranty, yet not expose yourself (The Company) to claims, risk, or litigation.
 
#52 · (Edited)
Concrobium: Interesting that the listed active ingredient is Sodium Carbonate (washing soda).

The listed ingredient on the MSDS is TSP (Tri-Sodium Phosphate).

www.concrobium.com/faq/

"Sodium Carbonate is the listed “active ingredient” on the Concrobium Mold Control label, but in fact there are two other ingredients in the solution which, when combined with the sodium carbonate and the water, result in this patented tri-salt polymer that eliminates and prevents mold."

And then they go on to describe the resulting mixture a "polymer" - aka - a long chain molecule.

In any case, it is not a fungicide/mildewcide in the same category as those used to treat/kill wood rot molds - just basic off-the shelf chemicals that oxidize (burn) any organic compounds its put on.
 
#54 ·
True....and it works though. We're not talking about killing wood rot fungi. I'll admit that sometimes I'll use bleach based products for quicker cleaning. Products like concrobium just don't clean the staining as fast without extra scrubbing. I do rinse well, let dry and then treat with concrobium after. You just have to spray it on and let it dry.

I've seen the proof in my own house the last few years. Lots of fish tanks that evaporate so during the winter I had a few wall locations that would start getting mold, several times each winter I was cleaning those with bleach based products. Treated with concrobium and haven't had that problem again.
 
#53 ·
First, scrape and clean all that fricking silicone off. Then use Zep grout cleaner and a grout scrub brush. Then re grout if needed. Seal if needed. Then re caulk with Polyseamseal Tub and Tile caulk.


And just for the record, Depending on the circumstances I use straight chlorine on some tough mold issues. And diluted on others.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top