Grout Cracking

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Old 10-04-08, 04:56 PM
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Grout Cracking

My grout is cracking in between tiles. I realize this probably means my floor is not level. Is there anything I can do while regrouting to help stop this from happening again?
 
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Old 10-04-08, 05:53 PM
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Is this on slab or wooden subfloor?

Cracking in grout usually means your subfloor is moving, which is not good. Let us know what you have underneith this tile.
 
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Old 10-04-08, 06:18 PM
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I have plywood, and then 3/4" hardibacker board. It is only cracking in 2 areas of the floor. I tried regrouting a year ago, but the cracking came back.
 
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Old 10-04-08, 06:33 PM
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Ok.

There needs to be some homework done prior to laying tile on plywood subfloor.

Deflection calculation needs to be done to see if your joists are strong enough for tile.

Is there a way you can provide us your floor joist sizes. (2x?), joist spacing (center to center) and the unsupported span of those joists. Unsupported span is the length of each joist between a supporting member, like a wall below or a post.

The subfloor needs to be at least 5/8" exterior grade plywood.

Your cement backer board needs to be laid in a bed of thinset and screwed, then tiled.

Hardiebacker doesn't not have a 3/4" thickness, only 1/4" and 1/2".
 
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Old 10-05-08, 07:33 AM
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You need to find out why the grout is cracking and then fix the problem before you regrout?

Is there just cracking between 2 tiles, or are these long cracks spaning several tiles? Can you notice a pattern in the cracking? Are the cracks directly over a floor joist, a hardibacker seam or a plywood seam? How thick is the plywood? Was the hardi bedded in a fresh bed of thinset before screwing to the subfloor?

Oh yeah, did you properly gap, tape and mud the joints between the hardi sheets?
 
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Old 10-05-08, 08:01 AM
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There is cracking in between 2 sets of tiles, cracks are perpendicular. I dont know if it is over a hardibacker seam or plywood seam as I do not want to take the tiles out.

Thinset was used between hardibacker and plywood and screwed in. I did mud the joints but I dont think I taped them. Not sure what you mean by gap.
 
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Old 10-05-08, 08:04 AM
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I used a 1/2 and a 1/4 hardibacker to bring the floor height up.
 
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Old 10-05-08, 08:41 AM
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I used a 1/2 and a 1/4 hardibacker to bring the floor height up.
Clear this up for me. Is the 1/2" plywood over another layer of something (like another layer of plywood, osb or planking), or is this the subfloor, directly over the floor joists? If the 1/2" plywood is the only subfloor material, you have serious problems there.

Thinset was used between hardibacker and plywood and screwed in. I did mud the joints but I dont think I taped them. Not sure what you mean by gap.
By gap, did you leave 1/8" space between each plywood sheet for expansion/constraction? If you dont leave a gap for the plywood to move, the butt edges will create upward pressure at the seams as the plywood expands and has no where to go. Did you leave a gap between the hardi as well?

Not taping the joints, is a problem. Hardi and all other cement board underlayments require that you do so. This could be the cause? How long are these cracks? I know, 2 tiles but you dont say what size tile?

I dont know if it is over a hardibacker seam or plywood seam as I do not want to take the tiles out.
Do you have access from the basement below? If so, you can see if the cracks line up on joists, or plywood seams (if only one layer of plywood was used).
 
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