Can I caulk over grout?

Question

The grout in my shower wall corners and where the tile meets the bathtub is cracking or completely missing in some areas. Can I just caulk over this, or do I really need to remove the grout first?

Bob H. · Answer

Theoretically, you should use caulk, not grout, where one plane joins another, such as where the wall meets the tub and even where two walls meet. Grout will crack if there is any slight movement, so you're better off removing anything that's deteriorating.

Despite that, I have used grout successfully on vertical corners in showers. I'd never use grout between a tub and a wall.

If you want to get a nice look at a small extra expense, buy "grout caulk," which is caulk made by grout manufacturers to match shades of their grout.

Erik B. · Answer

Some good info above and some bad info above and some missing information or context.

for the sake of knowledge, movement issues that cause cracks in grout need to be addressed in the building practices below the surface. Change of planes in any structure (not just tub surround)will show movement more easily then single plane.

In the tub area... the 2 studs in the both inside corners need to be attached together with screws. This will prevent most movement.

the use of a mesh or fabric tape applied with thinset in all seams ESPECIALLY the inside corners is the next step.  Following those 2 practices will stop all cracks 99.9% of the time.

now, since you cant address the underlying issues. You need to do what you can. You need a flexible product to join the 2 planes together either caulk, silicone or grout caulk.

Silicone is the most durable but a pain to remove when you need to do this again

Caulk works well but will need to be redone more often. But is easier to remove

grout caulk is the best option IMO for appearance and function.

If the cracks and gaps are large i would remove the grout and fill with one of the above. Make sure the area is DRY. Use paper towels and a blow dryer. Any moisture trapped will just cause mold.

If the cracks are small or hairline cracks you can most likely go over the existing grout with no issues.

Where the tub meets the wall there should be no grout EVER. There is way to much movement at this junction especially with these new flimsy tubs. (Cast iron on a solid surface you could sometimes get away with it).

heres the secret with caulking the tub joint.

Remove the old grout or caulk. MAKE SURE IT IS DRY!!! clear any debris or dust. .

FILL THE TUB WITH WATER. Fill it up as much as you can. This weighs down the tub and stretches that joint. When the tub is full then caulk the joint between the tub and wall. Let caulk dry fully before draining water.

You can do this with a shower pan also but use weights  or something really heavy  to  weigh it down.

FYI caulk and grout caulk clean up with water and is more user friendly. You can use a regular grout sponge to make a smooth joint.

Silicone takes a little more skill or knowledge to make a nice clean joint and not make a mess.

Jim K. · Answer

@Adam F.

Getting rid of grout is easier than most people think. Use a carbide blade on an oscillating tool, rather than the purpose-made grout-removal blades they sell to mount on recipro saw.

This is kind of why white as a bathroom grout color never goes out of style. The best caulks to use in the shower are the 100% silicone formulations, and they usually only make those in clear and white.

Scott P. · Answer

Although my tile guy recommended against it, I used clear caulk over grout once.  After a few years, i don't remember how many, I got mold between the clear caulk and the grout.

I was easy enough to chip out and regrout.

I don't really understand how mold could grow under caulk and between grout.

So...I would be removing bad grout and regrouting.   I'd skip the caulk.

Matt M. · Answer

@Adam F.

I’ve been tiling for 10+ years. Tons of showers. I always grout, then a bead of clear silicone where the tub meets tile (over the grout). Never had a call back. It keeps the grout from cracking, and makes for a water tight seal.

George W. · Answer

I would remove it first. It's alot more work but it'll end up looking neater and seal better.

Eric Williams · Answer

I used a premium bathroom caulk and went right over cracked grout ano no problems. also hit where the tub meets the floor to protect water from getting in any gaps causing leak below.

Matt M. · Answer

@Adam F.

I’ve never had an issue for adhesion. Mold will grow where it wants.

In one of my bathrooms I have a bathfitter fiberglass surround and the fiberglass tub liner that they do (was there when I bought). I have to re-caulk one a year. And that’s cleaning out the old caulk, cleaning well, then wiping with rubbing alcohol before caulking again. And that’s with anti-microbial silicone caulk for tubs. If it’s going to grow, not much you can do to stop it. Not sure why I only have issues at my house and not clients haha

Adam F. · Answer

@Bob H. @Matt Michaelson

Thanks everyone. The 2 reasons I've heard it's bad to caulk over grout is

1. The caulk won't seal to the grout well

2. The caulk will trap water between it and the grout, and mold will grow.

I think I'll give it a try first. Worst case scenario I need to remove it along with the grout, and re caulk.

Can I caulk over grout?

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