Hi SCC Pros,
This is an additional question regarding a project I mentioned earlier regarding the Deflection question where my client had a deflection test by a structural engineer for his new floors and the numbers were found to be L420 to L/600.
This customer has a general contractor who built an addition to his home.  This addition includes two new wood floors, a new 12x12 ceramic tile (walls) and pebble stone shower (shower pan), 18x18 travertine tile floor (with plenty of lippage), 12x12 ceramic tile floor (on the already existing part of the house) and a new limestone fireplace mantle and slate tile hearth built on the 1st level with 2x8 joists in a 11x14 open sun room.  The GC stated that this sun room floor was not built to handle the load for a tile floor.  It does have a heavy fireplace and wood floors.  Felt paper was used under the wood floor but not fully.  Under this floor is crawl space.
Half of the new travertine flooring (upper level) is on a pre-existing sub floor which is plywood that was nailed to the joists about 30 years ago and then two 1/4" layers of OSB that were also nailed.  The GC said the layers of the OSB were criss-crossed so the seams didn't run parallel with each other, and then nailed (not screwed).  There is also 1/2" OSB under the large ceramic and stone shower that was built into the new addition and the 18x18 travertine floor with every other joist being doubled. 
The customer is having problems with cracking of some of the tiles and has crackling and popping sounds on all the floor surfaces when walking on all these new surfaces.  The customer is very concerned that OSB was used instead of plywood and I am thinking the OSB floor boards are not considered to be the same quality as plywood floor boards or if they could be a cause of the issues.  I also don't like the idea that nails were used instead of screws.  Do you think the OSB is: a) too thin and b) not appropriate to be used for the weight load of these new surfaces? 
What are your opinions about using OSB and nails instead of plywood and screws for subflooring?

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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