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Can I Tile over Rigid Foamboard on wall

Riverpointhouse's picture

We live on the banks of a river After 3 major floods we decided to eliminate our slab on grade ground level living space, move that living space to 2nd floor and add a 3rd floor above.  Our old 1st Fl. Is now an above ground basement.  Overhead glass garage doors and food vents allow river water to flow in and out of this level.  Having eliminated all drywall, insulation, electrical and mechanical systems, the now “basement” wall section consists from outside to inside, of the following: A decorative ¾” exterior cement board, 1&½” airspace, building wrap, 4” old brick veneer, 1” airspace, 10” concrete block. 

We are looking to now cover the interior block walls, with 2” of closed cell rigid foam insulation panels ,secured directly to the concrete blocks and then cover the foamboard with large 1/4”porcelain tiles.  The space will be heated by gas forced air linear heater hanging near ceiling which iconsists of 5/8” green board, 8”of blown in open cell foam insulation and 1-½” of closed cell blown in foam insulation between joists, that keeps the floor and living space above very comfortable 

Our question is: Can tile be secured to the rigid foamboard using traditional  thinset?  Should a wire mesh be applied to the styrofoam board first ?  The idea is to be able to power wash the surfaces of walls and current tile floor, after flood waters recede.   Your thoughts and opinions would be greatly appreciated.  

There are many different (post #215919, reply #1 of 2)

There are many different types of foamboard. No doubt thinsetwill work on some, possibly all, but I don't know for sure. There are foamboard products like Kerdi -   that are made for that application. I use Kerdi as an example only. There are less expensive products made by other companies.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.

Expanded polystyrene will (post #215919, reply #2 of 2)

Expanded polystyrene will accept thinset and other cement-based products. My concern is the enormous amount of weight "hanging" from the foam. I think it wise to mud (thinset) your foam boards to a sound and surely fastened substrate such as OSB or 5/8" drywall. This allows the foam to be glued (thinset) AND mechanically fastened to the wall. Now you have a structurally sound and insulated wall system. Tiles are heavy! Make sure the bottom row of tiles bearst upon a structural member. The idea is to telescope weight to the foundation wall or some other sound structure (beam etc).

Mel Fros