We just had our master bath re-done. The grout in the floor tiles was applied unevenly in some areas (too low). When I pointed this out at the walk through, the construction mgr agree with me and said they would take care of it. I asked if they were going to remove the grout in the problem areas and they said no, it would be fine to just add more. I wasn’t home when they came back but now it almost seems worse - almost looks a little crumbly (it’s not moving now, but it doesn’t look good and I think it may end up crumbling). They are coming back again tomorrow to address this but my question: Are they right and it is appropriate to just add more? Or should they dig out what is there in the problem tiles and re-apply it? Thanks!
I’m sorry…I usually have an answer on construction stuff, but I don’t know much about this particular situation. I do know that it is very detailed fficult to dig out grout so they’ll do anything not to have to do that
If you ever find out the answer to this, please share.
I’ve watched YouTube videos about fixing grout and they show applying grout over old grout once crumbling parts are removed with a grout saw. But this doesn’t seem like something you’d want for a new floor.
We found significant water damage due to crumbling grout that wasn’t very obvious being in an inconspicuous place. We’ll probably have to redo the entire bathroom, and I’m considering options other than tile because I never want to deal with grout again after this.
The binding agent in grout is cement. Interestingly, cement doesn’t contain “glue” as such. Instead, the elements within cement bind to each other via a chemical reaction. The distinction is important to understand because grout (which is basically cement + sand) doesn’t adhere to other surfaces “on purpose” the way glue does. When cement or grout sticks to something, it does so because it has hardened in place - more like a pair of pliers gripping to tiny cracks and protrusions vs applying glue or epoxy to form a bond.
Where I’m going with this is that putting fresh grout on top of old grout will not give you a good bond as you surmise. That incidental sticking you’ll initially get from putting fresh grout on top of old grout will loosen over time due to movement (changes in temperature, humidity, foot traffic, etc). Ideally you’d need to remove the old grout as another poster mentioned, but that’s a messy and arduous process.
If you have wide grout lines, e.g. 1/4" like for saltillo tile, I’d probably be ok with putting fresh grout on top of the old as you’d have a decent amount of surface area to help the new grout stick. For 1/8" lines, I’d be more wary. If you’re using natural stone or rectified tile with 1/16" lines, then an epoxy grout or unsanded caulk (grout caulk, not regular caulk) would be solutions I’d be ok with.
"We found significant water damage due to crumbling grout that wasn’t very obvious being in an inconspicuous place. "
@MACmiracle - grout is not the culprit. There must be something else going on there, like water spilling into an area that does not have a waterproof barrier under the tiles. It is likely that your grout has been crumbling because there was moisture collecting in that area. You need to make sure that is taken care of before doing any cosmetic work.
@BunsenBurner We’re going to have it gutted down to the studs to make sure we aren’t missing anything. The house is older and it looks like the grout in a section of the shower broke down and water seeped behind it and travelled benind the tile wearing away the wallboard behind the shower and shower doors before making a hole through the floorboards under the floor tile. #-o
It’s a common misperception that grout in a shower is intended to be waterproof, and that the grout and tiles in a shower provide a waterproof barrier to protect the backboard. Grout is actually porous and allows water/moisture to pass through. Wet installations like showers need a waterproof barrier behind the tile, like RedGard or Kerdi. A waterproof barrier is important not only to protect the wallboard but also to prevent moisture from getting into your framing and causing mold.
A lot, a ton, way too many(!) tilers/contractors either don’t know about installing a waterproof membrane or just don’t care. When interviewing contractors for your new shower, be sure to ask them what sort of waterproofing system they plan on using and also how experienced the particular sub-contractor is with it. And fyi “don’t worry we use Green Board” is not an acceptable answer!
Thank you @anomander! That’s really helpful!
We’re getting estimates and that is something I didn’t know about so I will definitely ask the contractors who come over about it.
Can the waterproof membranes be used under floor tile, too? At this point I want to seal off everything I can. We’re even looking into avoiding tile altogether, but those options aren’t as attractive to me. I don’t need fancy, I just don’t want something I hate.
I guess I should stop hijacking now…
If you google shower pan construction you can see the shower pan has many layers. Slope and weeping holes are key.
I’ve been through lots of remodeling. Grout can be tricky. I would say the technique you describe may fail. However, if you think it looks sloppy then the only real remedy is to remove the grout and start over. That’s a big job. I wasn’t real happy with a grout job once. Fairly thin, unsanded grout. I honestly don’t notice the imperfections now.
OK, @anomander - you are indeed the grout expert! Thank you for your help. The guy is here now and I’ll talk with him. I really appreciate it!
To answer the original question, yes, grout can be successfully reapplied over grout.
Thanks all. For the second time someone came out to address the problem and it mostly looks no better than before. The construction mgr. will come out with someone who just deals with tile/grouting to get it taken care of once and for all (fingers crossed!)