Natural stone is brittle and unforgiving compared to ceramic tile; it cannot withstand the flexing or movement that a subfloor might undergo under weight. If a subfloor is too flexible, the stone tiles or the grout lines will likely crack. Installation often requires adding additional plywood underlayment to increase the floor system's stiffness. Furthermore, the surface must be flat, clean, and free of any debris, contaminants, or movement-prone elements before the mortar bed is applied to ensure a secure bond between the stone and the substrate.
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What are the structural requirements for a subfloor receiving stone tile?
A subfloor for stone tile must be exceptionally rigid to prevent deflection, which can cause cracking. Structural requirements include minimal joist deflection, typically L/720, and a subfloor assembly that meets local building codes for live and dead load capacity to safely support stone's weight.