sounds like the install is flawed. I would use a fracture membrane such as Schulter Detra when installing the new tile.  Yes, deflection should be L/720 for stone

On Mon, Jun 20, 2011 at 8:59 AM, Georgia <> wrote:
Hi all,
Looking into a project and wanted to get some of your thoughts.
This is a 1980's house with a new addition.  We did an initial inspection and read the contractors plans. 
In the upper level bathroom: The floor joists were doubled up on with every other joist on the 2nd floor.  Then, they added osb subflooring layed ontop of the existing subflooring and used screws to randomly secure the 2nd layer of subflooring.  They used the cheap grey MAPEI thinset $10/bag when installing the 18 x 18 honed travertine. No mesh tape was used in the seams of the concrete board.  Within a couple of days, several of the travertine tiles cracked.  In addition, they used sanded grout and then a grout haze remover which not only turned the color of the travertine, they didn't clean it completely before sealing it with a solvent based sealer.  Needless to say, it is a mess!  This is why I was called in.
1st Floor Sunroom: also an addition to the house which is under this new bathroom I described above; has joists that are 2x8.  The size of the room measures 14x11.  The additional shower build near this sunroom shows that the floor tile was installed after the wall tile and from looking behind the shower wall through the tub access panel I saw that there were no 2x10's used at the base of the shower wall between the studs.  The membrane is just loosly hanging around.  The installer also used nails instead of screws for the backerboard. (In the shower and tub surround.)  The joint between the tub and the tile wall have a large gap which was only grouted.  It is about 1/4" wide.
When we discovered that there is possible movement under the tile and the wrong thinset, grout, etc. we explained it would all have to come out and be properly installed along with possibly needing more support.  The client called in an engineer who completed a test and the inspection states the deflection of the floor is from L/420 to L/600.  Am I correct in understanding that the deflection for a stone floor should be L/720?
I want to make sure this is a sound surface before I do any work to it.  Would these current deflection numbers be suffocient for an 18x18 travertine floor if the right thinset and installtion is completed?
Kind Regards,
Georgia Rivera
Stone Buff, LLC
919.341.2873 Raleigh Office
910.730.1002 Aberdeen Office
919.609.5665 Mobile
1.877.664.4376 Fax

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