I keep a spray bottle near my shower with a mix of bleach & water, about 30% bleach and spray the problem areas weekly. Be sure that the shower is not very wet when you spray or the moisture will dilute it even more.

For some reason, you've provided mold a nice home in which to grow. You need to be a less hospitable host. I'm suspicious as to the detailing between your floor and wall tile. I'd eliminate whatever is between them now completely, and pump the joint full of 100% color matched silicone. If that didn't do it, I'd start looking at more invasive and expensive cures.

Last summer my brand new shower grout never fully dried and as a result I had mold. After the issue was corrected, i.e. Shower was redone, I now never need to use a mold elimination product at all. I have not had any mold since the redo in November.

Is your shower pitched properly? Is it draining well? Or could the grout be wicking undrained water from the pan and thus never fully drying? Do you use a properly sized fan with each shower?

Good luck.

Thanks girlnamedgale .. I'll check into that.

Joseph Corlett, LLC , forgive my ignorance, but can mold not grow on silicone? Is that why you suggested it. I feel like this could really help, although I feel I have too much moisture sitting in the shower.

I have a 90s builder grade home with the original fan so I'm pretty sure the fan isn't doing the best job.

roarah , my shower/grout sat for a couple weeks before we used it (because we were waiting on the door to get installed) so I'm pretty sure the grout was fully dried.

As for the pitch, I'm not sure. It does drain well. Shower was professionally installed with a wedi system. I do believe my fan is under performing.

"Or could the grout be wicking undrained water from the pan and thus never fully drying?" Maybe ??? I had to read this three times and I'm not sure I understand completely...

I should add that I had this shower installed early 2015. I'm embarrassed to say that I didn't clean the grout (not even once) for the first year and a half, maybe longer. I think the mold started getting really noticeable mid to late 2016.

We started drying off at least the corners of the shower enclosure at the end of every shower when we redid a bathroom to put the house on the market and had a 2 hour notice for showings.

Honestly that worked so well that when we moved into a new house and started redoing the bathrooms we started drying the shower enclosure tile completely. This bathroom does have a decent fan but it is in the basement and there are no windows at all and it's dark. No sign of mildew at all in three years of continual use. (And the liner of the shower curtain does occasionally show a little at the hem). And no scrubbing of grout needed. The tile has been cleaned in general with Scrubbing Bubbles but no stain or sign of mildew in the grout or caulk at all.

It only takes a minute. Maybe if you do that it will at least greatly slow down the development.

How do you not clean the grout on a shower floor for a year and a half? You somehow skip the grout when you scrub the floor?

I do not clean my grout or scrub my shower floors and have zero mildew. I squeegee the walls, glass and floor after use, takes less than a minute, leave fan on for 30 minutes and once per week spray with vinegar but no scrubbing, and rinse with hot water. I have never used glass cleaner on my doors either and they are as clean as the day they were installed last September...

Featherbe, by grout not drying I meant that after a few days of no use and a fan on 24/7 if I took a paper towel to the corners of my shower it would seep water. This was because of an install flaw. I too had a pro installation and waterproofed it with a kerdi pan and membrane but something went wrong and the shower never fully drained and my grout was always dark because water was trapped between the pan and the grouted tile. I use to squeegee the same than as I do now but due to constant moisture had mold...

Now that the pan works and drains correctly I have no mold with less than seven minutes per week of maintance...

edited to add pictures of how much fixing my drainage issue improved the appearance of my grout.

This is a picture before my shower redo. The grout in many areas never returned to its dry color, you can see water seeping from the corner walls...it was breeding mold!

this was taken days after a shower

And this is now after the redo. This is less than two hours after use and more than six months after install with not ever a scrub or more than a daily quick squeegee and weekly vinegar spray.

Mold cannot grow on silicone.

Yours is a detail problem; try the easiest fix first, please.

Thanks for the details and explanations roarah. (oh, and beautiful shower btw)

This morning after my shower I switched things up. I usually only squeeze the glass but this time I did the all the walls and floor. Then I took a dry cloth and hit the corners and areas where the walls meet the floor. I then left the door open and kept the fan on longer than usual. I'm going to try and keep this routine going and see if the mold comes back.

I'm convinced for now that I just had too much moisture sitting too long after showering. I will check closer over the next few days, but I believe my grout dries after showering so I'm hoping it's nothing underneath.

If additional wiping down and drying doesn't help then it'll look into Joseph's suggestion of silicone.

Thanks palimpsest !! I'm hoping my new routine (similar to the one you mentioned) keeps the mold away :)

MongoCT - thank you for the explanation and weed example. Things are making sense now :)

I'm looking into Concorbium now!

I mention Concorbium because it's usually available at the box stores. There are regional differences in what the box stores carry, but Concorbium or an equivalent.

MongoCT - it looks like I can order from Lowes. Is this it-

https://www.lowes.com/pd/Concrobium-68-oz-Liquid-Mold-Remover/4741343?cm_mmc=SCE_PLA_ONLY--Paint--ThinnersAndSolvents-_-4741343:Concrobium&CAWELAID=&kpid=4741343&CAGPSPN=pla&k_clickID=646ae8a6-86b2-483f-9093-96daddb181ec&gclid=CjwKEAjw4IjKBRDr6p752cCUm3kSJAC-eqRtcUcvP6pEyFv-0upC_R6oc3gGqRPDWvTrPfOXOUjkExoCy_bw_wcB

If you have black mold on your grout, I think there might possibly be a problem with the way your shower floor was constructed. There should not be any mold growing at all in a shower that dries properly. We had a similar problem with the shower in our master bath and during the demo for the new shower the tile setter discovered that there were tree roots coming up from the ground which was causing the wetness that caused the mold. (I live in Florida where things outside tend to want to grow inside too :-)). He had to treat the walls with an antimold product and the shower bed also got redone. He did a Kerdi shower and we have not seen one iota of mold since that time.

I'd recommend the regular Mold Control over the outdoor hose-end sprayer version that you linked to. The Mold Control comes in quarts and gallons:

Thanks Mongo, I'll find that one :)

jerzeegirl - I think my laziness is the reason for my mold issues. I believe my shower was properly installed and I'm convinced that if I dry the walls and floors better, leave the door open after showering, keep the fan running, then the mold will stay away... We shall see.

I didn't get a pic before the floor went down.

While dilute bleach (alkali) is a great disinfectant, vinegar (acid) is more effective in killing mold.

Please do not mix bleach & vinegar together, the chemical reaction causes harmful gases.

Some great information above.
Whom ever installed the tile did not caulk (silicon grout caulking) around the parameter of the floor properly, thus allowing moisture to collect under the tile on the wall. I agree with Joe about adding additional caulking here to stop the mold growth. Most grout products have a matching color silicon grout caulk available. You're not stuck with just the standard stark white or brown caulk colors.

The photo you posted of your shower prior to wall tile being installed shows no moisture barrier being. Cement board is not a moisture barrier. Can you confirm that one was installed? This also could be a clue as to why you're having so much trouble with mold.

"The photo you posted of your shower prior to wall tile being installed
shows no moisture barrier being. Cement board is not a moisture barrier.
Can you confirm that one was installed?"

The previous photo shows Wedi Board as the tile backer. Wedi Board is an appropriate stand-alone tile backer board for a shower. It does have a cementious surface coating that looks similar to cement board, but it is a different animal.

Wedi is A great system . I have installed many wedi showers. Heres a few things I can share.

If your tiler Installed all of Wedi Properly and used The *****PROPER WEDI brand sealant ON EVERY SEAM., the system is very solid. A wedi shower build mixed with porcelain or dense glazed ceramics and good grout will Dry out very fast after use, this means they dont retain much water if installed correctly. Things like the pan being set level, mortar selection and application, 98% coverage and proper key in. followed by pure silicone changes of plane and its pretty much a home run for me.

If you called me to your home to investigate this problem, id first get a complete and detailed list of what CLEANING CHEMICALS you tried several of..... id politley advise you , you may have worsened or created this issue. :):):).... and how you applied them and removed them and mixed them.

There is a reason we use Tile specific cleaners in showers and other than the Vinegar, Dawn, baking soda type remedies I dont veer to far outside of using ANY cleaners that aren't specific for the tile/stone and grout you have and I wouldnt be online taking random advise. I 'd call the MFG of wedi, or the Thinset/grout MFG, or the, Sealers/cleaners MFG Tech support. This is how the tile pros deal with these issues, direct from the horses mouth when problems arise.

What I would be be looking at ( after what chemicals have been introduced) Id be asking for pictures of setting materials used to set all the tile, Id inquire about curing and dry times and focus on the possibilty you may have either latex leaching from a latex based caulk in the assembly, Or A Bucket ready mixed setting material in the vien of mastic or a new age grout not meant for submerged applications. Could be as simple as Using latex sanded grout caulk in the pan that will mold.

Rest assured body and soap scum, in a properly built shower with the properly applied materials would have a real hard time producing this effect in a Wedi or topical waterproofed shower. . How is your bathroom ventilated? the fan runs after each shower? the windows get opened? etc etc.....

Eliminate what chemicals you used that may be causing this and inquire about Grout, mortar, mortar coverage, Sealants at change of plane and the proper Wedi sealant was used. If your installer wont help you here id first call Wedi and request a site visit from there rep.

My free advice to you based on My years of hands on Industry proven tiling experience and Wedi expertise.. -best

Tundra, is a fifty fifty vinegar/ water solution ok on porcelain and grout. It was what my tiler orginally suggested to me but I trust your judgement more. We are trying to be a chemically free clean house due to a cancer diagnosis last year but I would consider a product occasionally used if it is safer for my grout and tiles. Thanks

Hi Roarah,

I use mainly tile lab or Miracle seallants for cleaners, and id suggest calling them directly to find their safest cleaners for your chemical sensitivity and specific to your tile/grout. Vinegar I use mainly for efflorecense upkeep.

For your shower the main issue with distilled vinegar is stone curb, Its also prone to strip color from cement grouts over time, Just like sulfamic acid would and some grouts do not accept any acidic cleaners.. I only suggest using a vinegar/dawn/water solution as a problem solver rather than maintanance cleaning in showers.

It will not effect Porcelain but could effect some tile glazes, and coated porcelains so I dont randomly tell people to use it unless its my client and I know the tile.. It can be a gamble with your grout and it can in extreme cases effect metal trims, glass coatings, and there is safer methods.

Vinegar for anyone reading along, while seemingly safe and natural is caustic and should be avoided unless you know EXACTLY what type tile and GROUT you have and i dont suggest a 50/50 mix for daily upkeep.

NEVER use vinegar on stones of any kind and do be careful with NEW age type grouts . as well as cement based.

Roarah, are you sure you have a bead of silicone in there?

That picture was my original non draining shower, it did not have silicone and you advised me in the fall to make sure it was redone with silicone at all change of planes and he did it properly on the redo. I believe I have epoxy grout now. I do not use the vinegar every day but do spritz once per week or two... I have marble counters in the kitchen so have not been spraying my curb to avoid etching.

Thanks!

of course thats the old one.

Epoxy, porcelain id not worry.. careful w/glass/stone/metal.-best