Common Substrates, Thickness, Deflection

There’s a lot of information (and mis-information) online about what constitutes a suitable subfloor for tile. The difficulty is that tile can be installed over a number of substrates, and each requires specific preparations to ensure a long-lasting tile floor.  Werner Armbrust Owner of Armbrust Tile Company located here in Santa Rosa is a professional tile installers with over 27 years of experience and has worked with a variety of tile substrates.

Plywood and OSB are the two most common materials used for floor decking, and typically they are 5/8″ or 3/4″ thick. In this scenario,we install 1/2″ cementious backer unit (CBU) resulting in at least an 1-1/8″ thick subfloor. If we install a second layer of wood underlayment (3/8″ plywood or thicker), than we would use 1/4″ CBU or Ditra on top.

Older homes may have a structural plank subfloor, and these can be problematic because they move so much with changes in humidity. In this case, we usually install 1/2″ plywood overtop and 1/4″ CBU or DITRA uncoupling membrane.


Deflection, or bounciness, can cause tiles and grout to crack or come loose, and the tolerance depends on what type of tile is being installed. For instance, ceramic tile can withstand more deflection than natural stone.

​Reducing Deflection

Adding another layer of plywood can reduce deflection and curvature of the sheathing between joists, taking care to stagger the joints and gap the panels 1/8″ on each edge. Armbrust Tile recommends using ring shank nails or screws, turning panels perpendicular to joists and not aligning joints with joists. In extreme cases additional joists, or post on concrete piers needs to be put in place to strengthen the floor system.

For more information, and an evaluation for your next tiling project please contact Armbrust Tile Company to schedule an appointment.


Werner Armbrust


Tile over Wood Subfloor

Armbrust Tile Company

Whether you're thinking about your next kitchen or bathroom  remodel  we're here to help you every step of the way. 


Armbrust Tile Company has been around since 1998, so we really mean it when we say we're here to help you. 



Custom Design