Grout Cracking, tiles moving, need info! [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


View Full Version : Grout Cracking, tiles moving, need info!

07-06-2008, 08:38 PM

I have had new tiles installed and the grout keeps cracking. Also I noticed the tiles are moving.

I am looking for a good understanding of what is needed compared to what I have.

What I have:

Joists 2x8 Douglas Fir
16 IOC
subfloor is 1x6 Douglas fir at a 45 degree angle to the joists, NOT T&G
wire mess with float.
12x12 porcelien tiles
sand grout

I have checked the Deflecto calculator and it does not meet requiremnts.

Can someone explain what I need and why this is failing so I can have a good educated discussion with the contractor?


Sponsored Links

07-06-2008, 08:44 PM
Welcome, Frustrated. Please give us a first name to use, preferably in a permanent signature line. :)

What is the unsupported span of your joists?

What is below this floor?wire mess with float.I presume you meant "mesh," but I can't be sure with your title. :D

In any case, please be more specific. What kind of mesh. What are you calling "float"? How thick is this float?

With what were the tiles adhered to the substrate?

That'll get us started.

Brian in San Diego
07-06-2008, 08:53 PM

You probably have more than one problem. First of all, the deflecto is a tool to determine if you have the required deflection (or lack thereof) to support a tile installation. You say you don't and I'll take your word for it since I couldn't verify that without knowing the unsupported span of those joists. The second thing you need to do is prevent deflection between the joists. I am guessing, but from your description it sounds like your contractor is installing a "Jersey Mud Job" over your 3/4" dimesnsional lumber. I think your floor is failing for two different reasons, the joists are not sturdy enough to support the installation and there isn't sufficient subfloor to support it either.

You need to either sister the joists or you can shorten the span by installing support somewhere along the span. I also think you should install a minimum of 1/2" plywood over your dimensional subfloor and install either hardiebacker or a membrane like DITRA. Jersey mud jobs are not recommended much around here. we may need a little more info to properly assist you. Is this over unfinished areas? Could you install a wall intersecting the span?


07-06-2008, 09:18 PM
I believe the mesh...not mess:) was stapled to the 1x6 subfloor and a thinset was applied overtop. Not sure the thickness. I am not sure the thickness bond coat, but I believe it to be 1/4 to 1/2" The tiled area is 12'x18'. The span of the joists from support to support is 12" The contractor has put 3 2x10x8 to try and strap the joists together. It is located in the middle of the floor area where a 4x8 kitchen island with 1 1/4" granite sit. It is an unfinished basement underneath the tiled area.

Damir Stipanovic

07-06-2008, 09:50 PM
I believe the mesh...not mess was stapled to the 1x6 subfloor and a thinset was applied overtop. Well, Damir, I hate to be the one to say it, but that installation never had a chance of working. :(

That sounds like what is commonly referred to as a Jersey Mud Job and it doesn't work even over far more suitable subfloors than yours. Trying to use that method directly on top of a sawn board subfloor is just suicidal from a professional installer's standpoint.

It is possible to install a mud bed over such a subfloor, but it requires a cleavage membrane and a minimum of 1 1/4 inches of reinforced deck mud to make it work. What your guy did isn't even close to what was needed for that method.

In the alternative he could have installed a minimum of half-inch plywood and a CBU or isolation membrane under the tile.

Not sure just what you mean about what he put under the center of your joists. Were any extra supports installed that went down to some structure on the basement floor?

My opinion; worth price charged.

07-06-2008, 10:12 PM
He installed the 2x10x8 across the joists. He used lag bolts and construction glue and installed the 2x10x8 perpendicular to the joists(flat against them from underneath). The joists run 12ft to the support and the room is 18 ft long. He tied the joists together. The rational was to distribute the weight of the island across and reduce the flex.

Damir Stipanovic

07-06-2008, 10:25 PM
Well, that will help keep the joists from twisting, as is usually accomplished with cross-bracing or blocking between joists, but it won't really reduce the overall deflection. For that you must either add joists (sistering) or provide some mid-span bracing from below as with a wall or posts and beams.

I'm hoping you can work something out with this contractor, 'specially if he's already been paid, but I really don't see much possibility of any fix that doesn't begin with tearing out what you have and starting over.

Maybe someone else here will see it differently.

What's your geographic location?

My opinion; worth price charged.

07-06-2008, 10:48 PM
Winnipeg, MB. Canada is my home. So, I guess, rip out the tiles, 1/2 plywood, Ditra and new tiles should do the job:) The good thing is the general contractor is willing to work with me. He has been very good up to know with other issues. (Added a second storey addition to a bungalow and new floor plan on the old part). He has a new tile installer/contractor now. If all else fails...small claims court and a letter to BBB.

Damir Stipanovic

07-06-2008, 11:08 PM
You'll wanna do something about your joist deflection problem, too, Damir, before you do any tile replacement. Before you install the plywood subflooring layer, actually.

My opinion; worth price charged.

07-07-2008, 12:00 AM
I just redid the deflecto test. The Douglas fir was measured at 1.5"x7", 16" OC, span is 10.5ft. According to the deflecto machine, my rating is L/389 and L/360 is good for tiles. I can not do joist sistering since I have electrical wires running through the joists. Any suggestion, of how to try and stiffen the joists, I do have that big chunk of granite weighing things down?


07-07-2008, 05:41 AM
Damir, that chunk of granite is considered a "dead" load, since it will always be there. If you are going to install ceramic/porcelain tiles on the floor, then you don't need to do anything to the joists.

07-07-2008, 06:59 AM
Thanks Bob,

Hopefully my measurements are correct. With a joist length of 10.5ft, I am good, with 11 ft, not so good:)



07-07-2008, 07:40 AM
Hi Damir,
Once you are sure of your deflection you will still need to add 1/2" ply over the 1x6 subfloor and then either a 1/4" cbu or an uncoupling membrane like Ditra. The method your tiler used - mesh and thinset (Jersey mud job) is simply not an acceptable or approved method of installing tile.

07-07-2008, 07:46 AM
Well, good morning, Joe. We didn't wake you did we? :D

07-07-2008, 07:49 AM

07-07-2008, 06:04 PM
Earlier you said the span was 18'. Do the joists run that way or the shorter side? Keep in mind, the span is often NOT the width of the room, it is determined by what is under it supporting the ends. An outside wall, a partition wall, a beam, etc. could be a support and would shorten the total span. The piece that was bolted onto the bottom of the joists is NOT one of those, and should not be used to assume the joist span is shorter. So, make sure you are putting the right number into the calculator.

07-09-2008, 04:29 PM
It is the shorter side. I went into the basement and measured all the wood and lengths from supporting wall to beam.