Why are the same grout lines in our shower tile floor breaking down?

[stompy]

Certain grout lines are repeatedly failing (cracking, soggy, bulging, disintegrating) while all the other grout lines remain solid and never fail.

Refurbishment steps I take:

• I use a grout tool to remove the failed grout, all the grout between the tiles
• Using a puddy knife, I’ve pressed paper towel into the opening between the tiles to wick the water. The paper towel will remain damp for at least a week, but I leave it this way for a month.
• I’ve built some thin piping / duct work to blow hot air from the furnace duct directly into the opening between the tiles (as the grout has been removed), and I’ve let it blow air for another month.
• Before regrouting, I thoroughly clean with a brush, vacuum and wipe with solvent.
• I use a fine sanded grout mix to re-grout as recommended by a tile specialty store, and then after a few days apply grout sealer.
• Lastly, I replaced the caulking around the base which I’ve removed prior to regrouting (which was in excellent shape to begin with).

Within a year, the grout has failed again and I start the process over.

This problem has been ongoing for 7+ years. There is no indication that water is leaking outside the shower stall or shower pan.

Unable to determine what is causing this and debating if I should try to repair again or have the shower replaced.

 

[WorthFlorida]

Somehow too much water is getting behind the tiles. Looks like small tiles and all the good grout and sealer, moisture works its self between the tile and grout.

If this the shower floor sitting on wood floor and substrate, the floor is flexing from the weight of the person causing the cracks. During the grout replacement had to many air pockets and were not fully worked out.

 

[Sponsor]

 

[Chucky_ott]

First thing you need to know is that tile and grout is not waterproof. In a traditional mud bed shower, the waterproofing is provided by a PVC pan liner. So, in this order, you'd have tile, mud bed, PVC liner, sloped mud bed, sub floor.

Water that gets through the tile will saturate the semi porous mud bed and eventually flow to the drain via weep holes.

What you observe with your paper towel staying wet for a month should be expected since the mud bed is probably saturated.

If the shower pan is properly constructed, I'm not sure if worry too much about cracked grout other than for aesthetic reasons. I'd agree with WorthFlorida that flexing of the subfloor is likely causing the cracks.

 

[Fitter30]

Joint smaller than 1/8" ? Are they sealed?

Everything Grout - Clay Imports

The Ultimate Grout Guide -All Your Grout Questions Answered | Clay Imports

clayimports.com

 

[stompy]

Somehow too much water is getting behind the tiles. Looks like small tiles and all the good grout and sealer, moisture works its self between the tile and grout.

If this the shower floor sitting on wood floor and substrate, the floor is flexing from the weight of the person causing the cracks. During the grout replacement had to many air pockets and were not fully worked out.

Appreciate your comments. I had wondered if the weight of us was causing some flexing, then cracking. Just noticed another small crack in grout, near the drain, that I've never repaired before.

 

[stompy]

First thing you need to know is that tile and grout is not waterproof. In a traditional mud bed shower, the waterproofing is provided by a PVC pan liner. So, in this order, you'd have tile, mud bed, PVC liner, sloped mud bed, sub floor.

Water that gets through the tile will saturate the semi porous mud bed and eventually flow to the drain via weep holes.View attachment 100954



What you observe with your paper towel staying wet for a month should be expected since the mud bed is probably saturated.

If the shower pan is properly constructed, I'm not sure if worry too much about cracked grout other than for aesthetic reasons. I'd agree with WorthFlorida that flexing of the subfloor is likely causing the cracks.

Appreciate your comments. This too is helpful.

 

[stompy]

Joint smaller than 1/8" ? Are they sealed?

Everything Grout - Clay Imports

The Ultimate Grout Guide -All Your Grout Questions Answered | Clay Imports

clayimports.com

Appreciate your question. I just measured and I all joints are just a hair over 1/8" (3-4mm).
I used "Pro Color Premium" sealer (picture of which is shown in my post) provided to me by a stone and tile specialty store. This sealant, unlike the sealant I'd previously used from Home Depot, goes on white and remains white, so as to confirm total coverage. I cleaned the grout with a hard brush + vacuum before applying.