Tile and stone require a stiffer framing and subflooring combination than finish wood flooring or carpet. Without knowing the thickness of your subfloor, the size of the joists and the spans and how the flooring is to be applied, it's impossible to give you an answer.

I usually use two layers of 3/4" plywood subflooring over 2x10s @ 16" o.c. with a scratch coat.

This post was edited by worthy on Sun, Jan 25, 15 at 14:35

Google the John Bridge Deflectolater and enter in the joists data to determine if your floor is stiff enough. Subfloor is a minor consideration compared to the joist height, spacing, and especially, the span.

Thank you both for responding. I went to the John Bridge Deflectolater site and entered in our data and the results came back as L / 1587. This was very helpful. Thanks again.

TruFlor makes a low-cost OSB sub-floor in several strength grades (Sheathing; Structural-1 Sheathing; Single Floor) and multiple thicknesses so you should tell us what was actually used. The grade stamp should be visible from below.

TruFlor is graded under the PS2 standard. Higher performance, stronger sub-floors like Advantech have an ICC Evaluation Service Report (ESR) number.

John Bridge's Deflectolater calculates the deflection of an individual floor joist under the maximum design load. It does not consider the strength, surface integrity or adhesion properties of the sub-floor.

TruFlor PS2 Sheathing Grade sub-flooring is suitable as a base for carpet or wood flooring ONLY. Resilient flooring requires the use of an underlayment board on top of the OSB Subfloor. I would include ceramic tile in that category as well. In fact I would not try to adhere anything to OSB. I would add a high quality underlayment board as approved by the tile installer and the manufacturer of whatever he is using to set the tile.

Thanks for the advice. I will talk to the builder and tile installer about adding a high quality underlayment board. I checked the grade stamp on the TruFlor as you recommended and it is the PS2.

PS2 is the standard used to grade all OSB panels, the "grade" would be Sheathing, Structural Sheathing 1, or Single Floor (a combination sub-floor and underlayment) with a span rating (16, 20, 24, etc.).

This brand of OSB is considered a "commodity" so it is marketed to builders rather than designers and architects therefore it is difficult to find useful information about it. You should be fine with an underlayment compatible with the tile setting method.