Need some feedback in ceramic install gone bad.

[Orlando]

Looked at a job I installed less than a year ago. Residential new construction, 12x12 ceramic over 1/2 inch cement board (went with 1/2 to meet height in hardwood area ) 1/4x1/4 trowel used for thinset under cbu, hot dipped galvenized nails, 1/4 x 3/8 trowel used for setting tile, all joints taped, cbu joints offset from OSB joints, engineered joists 9 1/2 tall 16 on center with support beam every 12 ft. Ceramic tile in kitchen has cracks running opposite direction of the floor joists. Floor is very stable, took a + 300lb buddy with me. I got under crawlspace and cracks are directly over the joints on the OSB. There is no flex in the OSB joints. OSB seems to be nailed solidly and I beleive glued to the joists. The builder of the house and the owner are brothers and both friends of mine so I have to be careful how I handle this. I'm all for biteing the bullet and fixing this but not sure why its happening.Dont want to just replace the tile until I find out whats causing it.

[hookknife]

could the OSB be swelling at the joints????? Is there a moisture barrier under the house to block moisture???

[Orlando]

I will have to check on moisture barrier. Thing is hardwood is in same area and no cupping in the 3 1/2 planks. The area where the cracks are is slightly bowed down not up so I really dont think the joints would be swelled

[Bill Watson]

So... no movement in the floor joists, no movement at the OSB joints which are glued and nailed, no evidence of moisture at the hardwood, 1/2' CBU, installed with thinset and "Galveys", no observed deflection.
What's left? Possibly inadeqate bond of the tile to the CBU?
Is the grout cracked too? Are the tiles cracked throughout? Or in a limited area?
Do any other components (cabinets, trim, sheetrock etc) show signs of stress?

[Orlando]

Tiles are all bonded tight. No hollow sounds tapping from one to another. Grout is not cracking ecept in a line where crack is going through tile. Only thing I can possibly wonder if OSB sheets were fit to tight together when installed ? I dont know if tha would cause this or not. I will have to go back and take some pictures and could do a moisture test into the OSB from underneath the crawlspace. I'm completely stumped. One of the main supports is aprox 2ft from one of the cracks

[hookknife]

Possibly the contractor didnt leave the proper spacing in the OSB joints to allow for any swelling and now that they might have swelled for whatever reason it is putting a pressure or stress at that point causing the cracking????????

[rgfloor]

It sounds like panelizing in a hardwood floor. That happens when the osb dries out and shrinks.

[Orlando]

Lets say the problem is the osb is fit to tight. Whats the remedy?

[Jerry Thomas]

Originally Posted by Orlando Lets say the problem is the osb is fit to tight. Whats the remedy?

I guess one would have to remove the tile and CBU then make relief cuts at the OSB seams with a circular saw. We are not supposed to be making relief cuts in subfloors, so to compensate for that you would need to overlay the relief-cut OSB with a BC grade plywood underlayment, then use either Ditra or 1/4" CBU over the plywood underlayment.

I am so sure that is the case anyway. For some reason the first thing I considered was the house may have settled or slightly shifted for some reason...... possibly a very high wind situation. Where I live we have had winds this year that wanted to lift a house of the foundation..... never seen nothing to beat winds like we've had this year. Just trying to confuse you even more...

[Floorguy]

You would think, when pulling one of those cracked tiles out, that the backer board would also be cracked, if it was set into mortar

[Orlando]

I havent tore any tile out yet, cbu will flex farther than tile

[Kman]

Is this mostly one crack running across the floor, or is it in different places along with of the room? And does it run completely across, or stop somewhere along the way?

[Orlando]

Kitchen is approx 10 x10. The first crack is in approx 3 ft and then 4ft over fropm that one. She said at first it was on tile but is starting to spread. They havent made it accross the room yet . They are about halfway now but am sure they will continue. They are not cracking across the end joints of the OSB, just length ways. Thank you

[Floorguy]

Is the OSB, T&G?

[Orlando]

3/4 advantech osb tounge/ groove. No movement from underneath when it is walked on