Re-Grouting a Stall Shower

**SAS** · 03-09-2012, 06:52 AM

I have two problems with the stall shower in my bathroom.

In many places the grout between tiles is worn away and/or mildewing.
I have mildew behind the caulk where the last wall tile meets the fiberglass pan.

Do I need to scrape out the existing grout before applying new grout? I know I need to thoroughly clean away any mildew and let the grout dry. Also, what is the best way to prevent getting mildew behind the caulk at the bottom of the wall?

**jadnashua** · 03-09-2012, 03:35 PM

To get a good grip on a regrout, you need to dig out at least 1/2 of the depth of the grout. Good ventillation and good housekeeping practices can minimize two of the three things for mildew: moisture, food, spores. You can't do anything about the spores, but if you can keep down the other two, you can keep mildew (or any mold) from growing. Using a fan, leaving the door or shower curtain open or wiping the walls down after use can limit moisture. Cleaning periodically can keep down the body oil, conditioner, soap scum, etc. that feeds the mold, but the biggest thing is the moisture.

**SAS** · 03-12-2012, 09:13 AM

I just noticed that the wall "bows" a bit in the middle. The tiles seem to be solidly attached. Does it still make sense to regrout, or should I be ripping everything off (and hiring someone to re-tile)?

**jadnashua** · 03-12-2012, 04:41 PM

It's hard to say. It could have been that way before they tiled it. Do you know what is behind the tile? If it is drywall, you should plan to tear out and rebuild.

**SAS** · 03-12-2012, 07:38 PM

I'm not sure what's behind it yet, but I suspect it's just drywall. We re-did another bathroom and it was drywall. I'm guessing that if I remove the spout or the plate behind the control valve I'll be able to see what's behind the tile. Assuming it's just drywall, does it absolutely have to be removed? If I regrout and caulk well, is it salvageable?

**dlarrivee** · 03-12-2012, 08:43 PM

Grout isn't water proof.

**jimbo** · 03-13-2012, 06:22 AM

Grout isn't waterproof, so tile on wall board WILL fail. The first symptoms usually show up at the bottom couple of rows. Tap on the tiles. If there is any mushy feeling, then it's time!

**jadnashua** · 03-13-2012, 11:07 AM

Showers (and tub surrounds) made with plain drywall (and moisture resistant stuff is not much better!) generally have a fairly short life. There are exceptions if good techniques and proper waterproofing are done, but tiling directly to them will fail in a wet area. If a shower isn't used much, the drainage is good, and there's good ventillation, they can last a good long time, but typical use, they're limited. If the wall wasn't bowed before they tiled, it may be a sign that the wall and potentially the studs behind it are swollen with moisture, potentially starting to rot, and there could be substantial structural damage.

**johnfrwhipple** · 03-17-2012, 08:10 AM

Can I ask you what type of tile is installed? We have ramped up our efforts here in Vancouver and over the last two months refused any sheet tile selection from our clients that fall apart when soaked in water for a couple of days.

Make sure you never use a tile in your shower's wet zone that falls off a sheet when your cutting it. It is safer to test a small sample than go all in on the job.

This water based adhesive is a great food source for mold and it could be that your tile selection is causing the failure here.

**LLigetfa** · 03-17-2012, 08:22 AM

I'm not following your logic there John. Tiles adhered to a mesh backer sheet only need to stay adhered long enough to be set. Once in place, the thinset holds it there, not the mesh backer. I can understand though not wanting to work with it if it falls apart during cutting. Some tiles have a sheet on the face that is meant to release by soaking but I'm sure you already know that.

I agree with not using mastic and not tiling directly to drywall.

**johnfrwhipple** · 03-18-2012, 09:11 AM

Originally Posted by LLigetfa

I'm not following your logic there John. Tiles adhered to a mesh backer sheet only need to stay adhered long enough to be set. Once in place, the thinset holds it there, not the mesh backer. I can understand though not wanting to work with it if it falls apart during cutting. Some tiles have a sheet on the face that is meant to release by soaking but I'm sure you already know that.

I agree with not using mastic and not tiling directly to drywall.

Not true LLigetfa. The adhesive on a sheet tile is part of the structure of the floor or wall assembly. Coverage should be under 20% ideally and many are over 70%. If this coverage is a waterbased the tile can pop free releaseing grout and making for an unstable floor. Also the adhesive provides a food source for mold and further makes things worse.

Always check these tiles with a soak test. The most simple thing you can do to ensure your tile choice will look good for years and years.

Don't trust the salesperson. Call the supplier - you might be surprised to find what you where sold is not recommended by the manufacture for a floor application in a shower.

**John Bridge** · 03-27-2012, 07:07 AM

While there have been problems with certain mesh backed products, by no means should they not be considered. If that were the case there would be few if any mosaic tile installations in existence, and I can assure you there are many.

In my forty years of installing tiles, including mosaics, I've never heard that the glue causes a serious mold problem.

**johnfrwhipple** · 03-27-2012, 07:01 PM

Simply soaking a mesh tile in water and watching the tile fall off is warning sign enough. In the past few months we have rejected at least 4 tile suppliers. Around the world there are countless examples of failed pool tile installs and the industry recommends checking with the tile supplier if it is indeed acceptable for use in showers or pools.

In your forty years of tile setting John I'm sure the business has changed a ton. It was not to long ago you learned about sheet membranes and brought your installs out of the dark ages. If you only didn't retire you could have learned how to install linear shower drains and more European Style Designs.

JW