Grout crumbling [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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06-02-2019, 07:11 PM
My son had a guy install tile in his kitchen guy put backer board over original

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06-02-2019, 07:16 PM
Tongue and goove flooring,laid tile then grouted now in the area we walk in the grout is crumbling replaced the tile and regrouted still starting to crumble no i don't want to call him back i don't think he knows what he is doing

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06-02-2019, 08:05 PM
First, without installing some sufficiently thick plywood on top of planks, it never works well...the planks just move too much. Second, he probably did not install the cbu in a bed of thinset, which is called for with every cbu out there. Third, without knowing the stiffness of the structure, even properly installing things over the top of it may not work. If you have access from beneath, you can assess that part by putting in your number to the 'Deflecto' tool above in the blue bar. Keep in mind, the length is not the room size, but the length from one support underneath to the next.

06-02-2019, 08:05 PM
Of course, that's from too much movement and flex in the floor. Could be several reasons for the movement. You would need to provide more details about the installation and floor framing.

Edit; Or what Jim said.

06-02-2019, 08:14 PM
I did notice that there are no bridges between the joists do you think if i install them it will help to stiffen the floor.

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06-03-2019, 10:13 AM
Bridging does nothing to improve the deflection numbers of floor framing assembly. Its intent is to keep joists from rolling.

Pertinent numbers are size, spacing and unsupported span of floor joists. Once that is known, we can give better advice.

Also, clarification of existing floor layers would be helpful. If you're talking about a strip floor like a conventional wood floor, that really shouldn't be in the substrate for tile.

06-03-2019, 07:04 PM
And that cbu he added doesn't do a damn thing except give him a surface to adhere the tile to. He should have thought about shoring up that floor long before the cbu went down.

06-03-2019, 07:36 PM
Now that floor is down what do i do to shore up the floor other than ripping it up or do i pull the tiles up and shore the floor up

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06-03-2019, 09:56 PM
Your joists might be fine, but you would need to check and indicate their width, height, length and spacing.

But, if you did not install any plywood, the planks will just allow the tile to come up again.

Nobody allows cement board directly on top of requires at least a 1/2" layer of plywood on top of the planks, or, remove them down to the joists, and install 5/8, and 3/4" is much better ply on the floor first.

Then, the cbu must be bedded into thinset with the proper fasteners and then the seams covered with alkali resistant mesh tape. It's easiest to do that while tiling, otherwise, you tend to end up with speed bumps. It's not like a drywall joint, the tile covers it up.

As mentioned, cross-bracing the joists does not change the deflection along holds them in place so they can do their job, and mostly become redundant once the subflooring is installed. They do change the resonant frequency of the floor, but don't change its overall strength. What you have is a distributed load. Blocking can help with point loads, but not with a distributed one that exceeds the capacity.

If your joists are NOT up to spec, it's tougher to reinforce it after without damaging things, but might be possible. That generally would require installing a beam or load bearing wall underneath it to shorten the spans of your joists.

Again, though, if you didn't put some ply over your planks, the install is doomed to failure. It doens't always happen immediately, but will.

06-04-2019, 03:49 AM
Gentleman thank you all for your help it is greatly appreciated

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06-04-2019, 10:16 AM
Two tile jobs wasted because didn't DIRTFt
Do it right the first time