Cracked tile

rgfloor · #1 June 8, 2007, 11:16 AM

Monday I am going to look at a cracking floor.

-23/32 OSB
-1/4 Fiberoc over mud and screwed
-2 x 10 joist 16inch OC
-Tile is 16 x16 porcelain

-Problem is it is cracking every 16 inches
-No moisture testing done
-No deflection test done

What are some of the things you would be looking for?
I'm hoping Bill or Bud will pop in and comment, I'll buy the coffee.

Danny Ferguson · #2 June 8, 2007, 03:39 PM

What is the span on the 2X10 joists? Floor levelness? Is Fiber rock like Hardi? Is the cracking in the grout joint or the tile? Are cracks paralell or perpendicular to joists?

Peter Kodner · #3 June 8, 2007, 05:09 PM

Aren't you supposed to be recuperating????? I'm sure that kneeling and standing, kneeling and standing is going to promote a healthy recovery

Floorguy · #4 June 8, 2007, 05:16 PM

You would be surprised how well I actually got around when I broke my leg. I could inspect, but not install.

rgfloor · #5 June 8, 2007, 05:38 PM

Peter, YOU are not my wife and certainly not my mother so SHHHHHH!

Part of recuperation is excercise, I have an accomplice(I mean driver)

who will assist me if needed.

Five days inside is already driving me batty. Gotta go, gotta go.

Kids screaming, wife crying but HOW does ayone sit still for 6 weeks?

I said I was going to LOOK at the floor.

Who said inspect? SHHHH If I write a report and get paid I'll never tell, I just took a look.

Jerry Thomas · #6 June 9, 2007, 04:30 AM

I don't anything about Fiberoc.... is it supposed to be taped like CBU?

You do need to check the clear span of the 2x10's and check what type thinset was used.... not a premixed product or mastic.

Bud Cline · #7 June 9, 2007, 01:44 PM

Keep in mind that none of the tilebackers offer any kind of structural support, also remember that the minimum floor thickness (MINIMUM) required is 1-1/8". The 23/32 (nominal 3/4") with the 1/4" tilebacker does not ad up to 1-1/8". More than 1-1/8" would of course be better as we all know. You wouldn't think that skimping by only 1/8" would make a big difference but whose to say. All published standards are MINIMUMS, MINIMUMS, MINIMUMS. It's hard to get this through to some people when they want the cost at a MINIMUM.

My best guess with the limited information offered thus far is: DEFLECTION BETWEEN THE JOISTS. I have to admit tho...this is a curious situation. I'd like to know how reliable these cracks are. Do the cracks appear every sixteen inches everywhere without fail? Is the basic subfloor T&G? Is the subfloor glued to the joists? Is there cross bridging between the joists? And of course - what is the unsupported span of the joists? Does the floor bounce like a trampoline when walked on?

Jerry Thomas · #8 June 9, 2007, 03:30 PM

Sounds like the grout is cracked to me ...

Floorguy · #9 June 9, 2007, 09:46 PM

I always understood it as 1-1/8" before any uncoupling panel or grid.

FlooringGirl · #10 June 9, 2007, 10:41 PM

Oh, crap. Quit being so mean, guys. You say you have 16 x 16 tiles, and the cracking is every 16 inches. At what spot in the tiles is the cracking taking place? At the joints, in the middle?
Tia

Bud Cline · #11 June 10, 2007, 09:10 AM

Not being able to be there to form an opinion based on a visual inspection the following questions still linger in my mind:

Do the cracks appear every sixteen inches everywhere without fail? Is the basic subfloor T&G? Is the subfloor glued to the joists? Is there cross bridging between the joists? And of course - what is the unsupported span of the joists? Does the floor bounce like a trampoline when walked on?

Others have also asked pertinent questions above that should they be answered would offer some needed input:

Is the cracking in the grout joint or the tile?
Are cracks parallel or perpendicular to joists?
Type of thinset used?

No one is being mean here, these are all questions that would typically have to be asked for someone to offer an informed opinion. Inspecting floor failures and determining a cause, all done via the Internet without an on-site appraisal is risky business. Even some pictures would be nice if they were to show some detail.

rgfloor · #12 June 11, 2007, 05:51 PM

Well, here is the info:
Tile cracked all the way thru parellel with the joist and starting to crack perpendicular in a 4x8 pattern. Then parrallel in some other areas, not on the 16inch joist line. These cracks are all directly over joist.
Subfloor is a single layer of 23/32 OSB T&G, no bridging of joist on 16 in center.
Span is 14 ft 9 inch
Homeowner says china rattles when you walk.
1/4 in Fiberock is installed with modified Versabond.

Looking for opinions.

Bud Cline · #13 June 11, 2007, 09:51 PM

Here's what I feel is taking place:

If the china rattles the entire area is overspanned for the first problem. The mentioned span is probably marginal but I haven't checked it out for sure. The room is a trampoline!

Based on the location of the cracks I also see flexing between the joists. Some of this flexing is due to the lack of joist bridging below, the joists are twisting under loads applied between the joists, that's the second issue.

The third issue is the modified thinset used to install the tilebacker. THAT thinset is to be unmodified. Theory being - unmodified will not stick to the substrate and will allow for movement between the layers isolating the tile installation from the structure.

The next issue is that the subfloor (4X8's) are not glued to the joists, when the floor flexes everthing flexes.

Bridging every four to six feet would be the place to start, then shorten the span, in this case it should probably be cut in half because of all the movement that's taking place.

Quite frankly I would be surprised if the subfloor was really 23/32. If it is stamped as such then I can't argue with it but I have my doubts at this point.

Those are my thoughts.............

Jerry Thomas · #14 June 12, 2007, 01:41 AM

Can you see the main girder RG? I believe there is too much deflection here.

My guess without seeing this is the girder is flush and not a dropped girder. If it's a flush girder the 2x10's will be notched and supported by a 2x2 ledger board nailed to the girder... if that ledger strip does not have 2 nails "directly" under each joist... the joist can slip down a little causing much bow and bounce in a floor.

Could be more than one thing occurring... is that type backer board supposed to be taped?

Jim Carlin · #15 June 12, 2007, 10:38 AM

I could be wrong on this and if so it won't be the first time. The deflection rate for a 2x10" joist with a span of 14'-5" is L/347. At 14'-0" it is L/380 which is just barely OK.
The criteria is for a deflection rate of at least L/360 for tile and L/720 for stone.
It doesn't matter if the joists are over the main beam, in hangers on the sides, or on a ledger, the unsupported span is still the same. The OSB would be OK if the span was shorter or the joists sistered. What goes on top of the OSB does matter, as it is dependent on how the tiles are going to be installed. I'm not familiar with Fiberrock or its specs., so will refrain from inserting both feet in my mouth. Just something to think about while sitting around the campfire with an adult beverage.

Jim

Cracked tile

Log in

Advertisement

Support TFP

This discussion, "Cracked tile", in Ceramic and Stone Q&A (part of the category Do-It-Yourself & Consumer Support), begins, "Monday I am going to look at a cracking floor. -23/32 OSB -1/4 Fiberoc over mud and screwed -2 x ..."