Cracked Tiles at Underlayment Seams

Reply

  #1  
Old 09-09-04, 03:05 PM
Muddycub
Visiting Guest
Posts: n/a
Question Cracked Tiles at Underlayment Seams

Approx. 8 mths. ago I installed 12"x12" ceramic tile, which has since developed a hairline cracks in two locations in the tiled area. I've removed the affected tiles (one line of three, the other a row of four), and had noticed that the crack manifested itself identically along the seam of the underlying hardibacker board. The hardibacker board did have thinset applied under it (as the manu. suggested), as well as it being screwed down at every premarked location on the board. I also taped the seams (which were staggered and not overlayed over the subfloor seams) and applied thinset to the joints. I asked for some help at the local home center, and they said that possibly the thinset in the gaps (which were ~1/16 - 1/8") had shrunk in, and that I should have left a small ridge of thinset at the seams overnight and then sanded them to a smooth finish the next day prior to installing the tile. Assuming that my subfloor is stable and does not have significant deflection (home ~25yrs old w/plywood subfloor and 16" joists OC), does this seem realistic? If so, for my own better understanding, how does that seam not properly being covered cause tiles to crack?

Lastly, upon removing those tiles, some of the 1/4" hardibacker board had stuck fast to the tile, and seperated layer(s). Thus, where tiles have been removed there is no longer a complete uniform thickness of hardibacker board. The home center suggested that I remove the hardibacker board sections where the tiles have been removed, and replace with a new section of same material (this time doing a better, more thorough jobs at the seams) prior to tiling. I was wondering if it would be acceptable to just fill the areas completely with thinset or something other as opposed to using small sections of hardibacker board and creating yet more seams in that small area requiring addressing?

Suggestions please.

Thank You.
 
Sponsored Links
  #2  
Old 09-09-04, 05:23 PM
floorman
Visiting Guest
Posts: n/a
When you say you fastened at the seams as the hardi backer was marked what do you mean by that?Every 4 inches,6,8?The guy at the store was grasping at straws here,you don't need to leave a ridge and sand the next day.Now did the tile crack or was it the grout?If the tile cracked there is a major problem that taping the seams would not have fixed anyway.
What is used for the joists? 2x 8,10 12?How thick is the plywood subfloor? And what is it made of o.s.b?plywood?particle wood?what size notch trowel was used?
If i were to guess at this point and this is merely a guess i would have to say that the hardi was not fastened properly from the outset.But we need more info before we can determine that,Also what size is the tile and what did you fasten the hardi with? Please get back to us and fill us in
 
  #3  
Old 09-09-04, 07:08 PM
Muddycub
Visiting Guest
Posts: n/a
Question

Thanks for the prompt reply. The tiles are 12" x 12" PEI IV (1/4" thick). The tiles themselves have the crack (hairline) directly in line with where the seam / joint of the underlying hardibacker board is. The perimeter of the hardibacker board has been screwed down with the manufactures recommended screws (specifically sold for that purpose; coated ~ 2" long if I'm not mistaken) every 6". The board has screws every six inches in any direction.

As for the joists, I'd have to look again to verify, but if I'm not mistaken, they are 2 x 8's (possibly 2 x 6's but I don't believe so). The subfloor is plywood 3/4" thick of which has 1/4" luaun board over (again screwed down ~ every six inches) and then the thinset/ 1/4" hardibacker / thinset / tile.

Thanks again.
 
  #4  
Old 09-09-04, 08:21 PM
A
Member
Join Date: May 2001
Location: canada
Posts: 673
Received 0 Votes on 0 Posts
Well, now that you've mentioned Luan, it's answers a lot of questions. It has no strength at all, and is one of the worst underlays you can get. It's very unstable stuff. 2x10 joists would have been the minimum size, so if they are 2x8 then they are under minimum spec. So, that may be the problem. Another layer of at least 1/2inch ply would have been better. BUT, you may find that after you replace the tile, they may not crack again.
 
  #5  
Old 09-10-04, 05:12 AM
Muddycub
Visiting Guest
Posts: n/a
Cool

Thanks for the reply. I'm going to give it another try (hoping for the best). My only remaining question however is what to do with the damaged hardibackerboard that was underneath the tile ?

My first thought was to remove that area of hardibacker board (that was directly underneath the removed tile), and replace with new, but then I began to second guess that because the perimeter of the adjacent hardibacker board (which actually would remain under the surrounding good tiles) may not be screweddown at the edge (could be several inches back).

I'm now thinking to remove the bad layer(s) of hardibackerboard, and rescrewing down whats left in that area, and then using just thinset to build backup and lay the tile ?

I'm not certain if either of these two options are worth a try, or if there is another option to try that would not be a drastic first measure.

? Thanks again.
 
  #6  
Old 09-10-04, 05:25 PM
A
Member
Join Date: May 2001
Location: canada
Posts: 673
Received 0 Votes on 0 Posts
That layering effect that Hardiboard seems to do sometimes it what I don't like about it...but I think your solution will work. Remove what is loose, and screw down the rest. You should be able to build it up level with thin set and the tile. Once you get the tile out, step on the area and see if you notice movement...it couldn't hurt to put in some blocking between the joists if you can get at it from below.
 
  #7  
Old 09-10-04, 07:38 PM
Muddycub
Visiting Guest
Posts: n/a
Smile

Thanks for all your help. It was very helpful. I did screw it down really well (especially around the layers of peeling). I then did the best possible job I could to level these tiles w/the surrounding ones by applying the necessary thinset.

p.s., I did check the joists, and they are indeed 2x10's. Hopefully all will work out. I guess time will tell.

Thanks again. Your replies were so quick. This is a great site!
 
  #8  
Old 09-11-04, 11:55 AM
J
Member
Join Date: Sep 2003
Location: NYC
Posts: 1,615
Received 0 Votes on 0 Posts
Just out of curiosity where where the tiles in reference to the span of the joists. If the cracks were in the middle of the span and it has no support I think that you should at least add some serious solid bridging to it.Try to make the floor as much 1 solid piece as you can If it cracked the tile once it will probably do it again since you really are not really changing anything.
 
  #9  
Old 09-12-04, 06:25 AM
floorman
Visiting Guest
Posts: n/a
Thats a good question joneq.Also does this tile go from say kitchen to a sun room or other area where the tile has to go over a transition in the foundation or other sort of wall or span that goes from on surface to another?How big of an area are we talking about in regards to how much tile was set?
Another problem could be the spacing of the screws,6 inches on the seams is a bit far i screw my underlayment at 2 inches on the seams and 4 to 6 in the field .I use durock and am not a fan of hardi backer either.
Not sure the 1/4 luan would cause any problems as it would become part of the subfloor equation with all the screws in it.However,i am convinced that 1 layer of 1/2 inch is a lot better than 2 layers of 1/4 inch.
Pull aline across the kitchen perpendicular to the crack in the tile and see if there is any kind of crown or valley anywhere around the crack that would contribute to this happening .Get back to us and let us know what you find
 
  #10  
Old 09-13-04, 07:23 PM
Muddycub
Visiting Guest
Posts: n/a
Originally Posted by joneq
Just out of curiosity where where the tiles in reference to the span of the joists. If the cracks were in the middle of the span and it has no support I think that you should at least add some serious solid bridging to it.Try to make the floor as much 1 solid piece as you can If it cracked the tile once it will probably do it again since you really are not really changing anything.

I'm not 100% certain, and will have to check that out. I should have an opportunity to look at tommorrow afternoon, and then I'll get back to you. I am certainly planning on resupporting that area however. Thank You.
 
  #11  
Old 09-13-04, 07:34 PM
Muddycub
Visiting Guest
Posts: n/a
Originally Posted by floorman
Thats a good question joneq.Also does this tile go from say kitchen to a sun room or other area where the tile has to go over a transition in the foundation or other sort of wall or span that goes from on surface to another?How big of an area are we talking about in regards to how much tile was set?
Another problem could be the spacing of the screws,6 inches on the seams is a bit far i screw my underlayment at 2 inches on the seams and 4 to 6 in the field .I use durock and am not a fan of hardi backer either.
Not sure the 1/4 luan would cause any problems as it would become part of the subfloor equation with all the screws in it.However,i am convinced that 1 layer of 1/2 inch is a lot better than 2 layers of 1/4 inch.
Pull aline across the kitchen perpendicular to the crack in the tile and see if there is any kind of crown or valley anywhere around the crack that would contribute to this happening .Get back to us and let us know what you find
The tiled area is relatively small (~90ft2 / in a Kitchen), and does not appear to go over any transitional area (especially where the cracks have been identified). At least I did not see any prior to laying out the lauan and hardibackerboard. I will stretch a line tomorrow and let you know what I observe. As for screwing down more around the perimeter, or at least closer, I was actually thinking of doing so w/the hardibacker board, but the manufacture had premarked locations which were six inches apart (perimeter and body of board). Interesting enough however is that I found "new" literature (at least something I did not see before) on the hardibackerboard stating to screw at two inches apart around the perimeter ! The hole locations around the perimeter are no where near two inches apart ! The only thing I can say is that I did screw down what was left of the hardibackerboard every two inches around the seams prior to relaying tile. FYI, the lauan board was screwed down every two inches around perimeter and every four inches in the body of the board.

Thanks, and sorry for the delay to your response.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: