Subfloor/Joist Questions when installing 12x24" tile

Reply

  #1  
Old 12-08-12, 09:01 AM
B
Member
Thread Starter
Join Date: Jun 2005
Location: massachusetts
Posts: 69
Received 0 Votes on 0 Posts
Subfloor/Joist Questions when installing 12x24" tile

Hi,
I have 20 year old ceramic tile 8"x8" with a subfloor and underlayment under the tile. I know the 2 plywood layers are biggerthan 1/2" but not 3/4". The sub floor was the mininum for hardwood floors.
The joists are 16" inch on center which I should have 12 inch joists on center under the kichen. I want to shore up my 2x10 joists by running perpendicular boards. Should I go with 2X10 or are 2x4 or 2x6 OK to run perpendicular to the joists as I am using for rigidity?
How far apart should the perpendicular boards be (4 feet)?
I did have all cracked tiles along all the cabinets which are on the outside walls. I had a 4" tile cut along all the cabinets and then a full 8" tile which a lot of them cracked as well.
When I put in the new cabinets, I had to shim all the cabinets by a little more than a 1/4" but all were consistent at 1/4". It seems the rest of the floor is level to the bottom of the cabinets now.
Was the house settling the reason why the tiles along the cabinets cracked or was it the 95 degree temperature installing them or my installation that caused them to crack?
I am going with 12 x 24" porcelain tiles. Any issues with that?

Thank
Brian
 
Sponsored Links
  #2  
Old 12-08-12, 09:34 AM
czizzi's Avatar
Member
Join Date: Jul 2007
Location: USA
Posts: 7,388
Received 14 Votes on 12 Posts
The tiles cracked because of movement. Any bounce in the floor will cause failure at the weakest link. Cross bracing will help stiffen up whats there, but you may need to beef up the subfloor as well. Give us more specifics - length and width of the room, maximum span of the joists, is there an island, verify the joists are 12" OC in the kitchen area and exactly what is down on the floor for a tile base as it sits presently.
 
  #3  
Old 12-09-12, 04:50 AM
B
Member
Thread Starter
Join Date: Jun 2005
Location: massachusetts
Posts: 69
Received 0 Votes on 0 Posts
For underlayment, I have 2 sheets of 23/32. My joists are all 16" on center that I plan to use cross-bracing. My kitchen is around 260 sq feet. I have 4 x 6 walkway into it and around 13 x 19 main kitchen area with no island. The only tiles (8x8) that cracked were the ones next to my run of cabinets. When I put in my new cabinets last month, I had to shim all cabinets about 1/4 inch from the outside wall.

One other thing, 20 years ago the guy that put in my hardwoods who would have done the tiles told me to put mortar in between the any gaps in the plywood which I have since found out that I should have created a 1/8" gap between the pieces of plywood.
 

Last edited by brianbo; 12-09-12 at 07:08 AM.
  #4  
Old 12-09-12, 12:46 PM
J
Member
Join Date: May 2007
Location: USA
Posts: 1,607
Received 0 Votes on 0 Posts
Brian,

23/32" is what's known as 3/4" plywood these days. All plywood is 1/32" thinner than its stated thickness.

So I guess you're saying the subfloor is 3/4" with a 3/4" underlayment over it. At first I thought maybe the layers were 5/8" (19/32') since you said it was the minimum allowed. The tiles are bonded to the ply right? If so, not a good method.

To sum up you told us you have 2x10 joists spaced 16". How about the span, species and grade of the joists? We can make no judgement without the span and would help to know the species and grade.

I have no idea what you plan to do by doing this;
I want to shore up my 2x10 joists by running perpendicular boards.
One other thing, 20 years ago the guy that put in my hardwoods who would have done the tiles told me to put mortar in between the any gaps in the plywood which I have since found out that I should have created a 1/8" gap between the pieces of plywood
Ply is supposed to be spaced 1/8" when installed. Some brands of thinset tell you to fill the gap, others say not to do that. Main problem may have been tiling right on the ply though, it's never good to do that.

I am going with 12x24" porcelain tiles. Any issues with that?
Yes, I hope your floor is very stiff and very flat. Let us know that answers to the Q's above.

Jaz
 
  #5  
Old 12-09-12, 02:19 PM
czizzi's Avatar
Member
Join Date: Jul 2007
Location: USA
Posts: 7,388
Received 14 Votes on 12 Posts
If there is not cross bracing, adding that will stiffen the floor. However, not being there, we can't access if you are "good to go" even though the specs on what you have seem good.

Do a little test if you could. If you have a self leveling laser put it in various places around the room, if no laser, place a glass of water in various spots and walk around. Hop around, shimmy around let the kids have some fun, whatever, but watch the water or laser closely. If the floor still has bounce you will see ripples in the water in the glass. A sturdy floor will not effect the water in the cup. Pay particular attention to the areas that previously cracked.

12" x 24" tile will be more likely to break than 12" x 12" if the subfloor is not adequate.
 
  #6  
Old 12-10-12, 05:03 AM
B
Member
Thread Starter
Join Date: Jun 2005
Location: massachusetts
Posts: 69
Received 0 Votes on 0 Posts
My mistake the 2 sheets of plywood are both 19/32" with 2x10 KD joists. My house is 28' wide and there is one joist running from front to back. I have a triple 2x12 KD as my center beam held up by lolly columns 7 feet apart.

If i add cross bracing to the joists, I would expect more rigidity to the floor as I have seen spacing 12" on center is more rigid than 16" on center. Should I use 2x10, 2x4 or 2x6 for the cross bracing?

If the floor is level, is there a cement board or similar product that the tile should be mortared on and can I lay it over the 2 sheets of plywood as long as my dishwasher will fit?

I am ripping up the old tile today. When I run my 3' level across the floor in different parts on the tiled floor, it seems level but I will know after it is ripped up.
 
  #7  
Old 12-10-12, 11:15 AM
H
Member
Join Date: Jan 2006
Location: USA
Posts: 3,524
Received 6 Votes on 6 Posts
Ok, 28í wide house with a center beam so the unsupported span of your joists is approx 14í. Without knowing the species, grade and condition of the joists, they may be overspanned. If that is the case, adding bridging or blocking isnít going to be the solution. You would need to either sister the joists or add a support wall from below to cut the span down to something more acceptable.

You had 8Ē ceramic tile that cracked near the cabinets. Describe the crack, was it straight, how long was it, did it happen right after you installed the tile or did it happen recently? What kind of plywood was used for the underlayment? Was it exterior glue plywood? How was the plywood underlayment installed? Did you stagger the seams so that they did not line up with the subfloor plywood below? Was the plywood underlayment installed perpendicular to the joists? Did you nail or screw the underlayment, and what was the nail/screw pattern? If you did not leave space between the plywood sheets for movement, that could be the cause for cracked tile as well. Can you tell if the crack is over a plywood seam? Your tile cracked for some reason. Until you figure out why and correct it, itís likely to happen again when you install the new tile.

As Jazman pointed out, installing the tile directly to the plywood isnít the best method. Itís best to use cement board or one of the sheet membrane products.

To install tile the size you want, you will need a dead flat floor and a very stiff, solid floor. Additionally, tile that size may be cupped, and if not installed properly youíll experience some unacceptable lippage.

You need to find out why your tile cracked, and correct the problem. Then you can move onto how to install the tile.
 
  #8  
Old 12-11-12, 03:52 PM
I
Member
Join Date: Jan 2012
Location: USA
Posts: 68
Received 0 Votes on 0 Posts
You should have installed like this 3/4" then 1/2" both perpendicular seams offset at least 12" apart. 3/4" ply alone is not enouph in my book but dont forget you also need a cbu or membrain mat like ditra. Not having one and the plywood is
not correct can lead to issues.
 
  #9  
Old 12-12-12, 08:02 PM
B
Member
Thread Starter
Join Date: Jun 2005
Location: massachusetts
Posts: 69
Received 0 Votes on 0 Posts
I ripped out the old tile and brought to the transfer station only $10. I had a professional tile guy come over tonite. He is over 50 and has contracts for a lot of commercial restauarants. He came in and said the underlayment plywood was put in wrong. All the underlayment pieces except 1 were parallel to the joists and only one was perpendicular to the joists which was not near the cracked tiles. The plywood sheers are butted to one another with NO gap.
My tiles cracked after year 2. The cracks in the tiles: some were hairline and some were bigger but all stuck to the cement. The smaller tiles (4 inch cut) were mostly straight. A few of the large 8" tiles had spider cracks in them. The vast majority of the cracks are not over a seam except where the bounce is. The run of cabinest is 12 feet.
I do have metal bridging on the joists, I thought extra cross bracing might help but from what I have found out it might not. The joists are in good shape.
Currently, I have some bounce by the cabinet on the end where the cracks occurred and I have squeaks in another area which did not crack. I have a feeling where the bounce is the seams of the subfloor and underlayment are on top of one another,

FYI: I did this when I bought my house (pre-internet). The builder was a builder, someone who did not care. He had his 17 year old son and his 17 year old friend who was fired after my house was built, lay the underlayment. I just remember there were very few screws in the underlayment. I told the builder that it needed more screws and he had the kid put more screws in and every screw was put in sideways. I then had to fix all of them and I was very inexperienced. The builder was a builder who had golf to play.
Now, I need to add more screws where the squeaks are.
The tile guy tonite said to use Ditra and I have a guy coming tomorrow who is a very good carpentar (lots of restorations of old homes) who over the phone said to use Dura-Rock.
One is a cement board and one is a membrane, Witch is better in my situation?
The tile guy said Ditra allows for some movement but he also said cement board does not add rigidity only for adhering which is the opposite of what the carpenter coming tomorrow said over the phone.
 
  #10  
Old 12-13-12, 11:34 AM
H
Member
Join Date: Jan 2006
Location: USA
Posts: 3,524
Received 6 Votes on 6 Posts
From your description, the tile guy is right and the carpenter is wrong. Cement board does not add any strength to the floor, it merely serves as a good bonding surface for the thinset and tile. Ditra is an uncoupling membrane and will allow for some horizontal movement in the floor. Its a premium product and would be better in your situation. Remove the second layer of plywood and install it correctly. The face grain of the plywood should be installed perpendicular to the joists. After removing the second layer of ply, make sure that the subfloor is properly screwed to the joists. Add as many screws as you need to make it rock solid. When installing the plywood underlayment, it should be screwed to the subfloor, not the joists. Use screws every 6 inches in the field and every 4" around the perimeter of the sheet. Leave 1/8" gap between the sheets for movement. Make sure that the seams of the underlayment do not line up with the seams of the subfloor. Use ditra instead of cement board. Ditra gets installed with modified thinset. The tile should be installed with dry set mortar.

Have you determined that your floor joists system is adequate to support a tile installation? From your description, the joists may be overspanned. You may have to sister the joists to stiffen them.
 
  #11  
Old 12-13-12, 02:21 PM
J
Member
Join Date: May 2007
Location: USA
Posts: 1,607
Received 0 Votes on 0 Posts
Brian,

Johnny said exactly what I would have said, word for word.

We'll wait for your joist-framing answers. Type & size of joists, spacing, unsupported span to the inch, species and grade if at all possible.

Jaz
 
  #12  
Old 12-18-12, 08:40 AM
G
Member
Join Date: Dec 2012
Location: Canada
Posts: 1
Received 0 Votes on 0 Posts
Wink Try IBS2000 floor bridging.

You may want to look at a product called IBS2000. Available at Luxor Industrial Corp..
 
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: