Ceramic Tile Subfloor Preparation

Tiling over Concrete and Wood Subfloors

By Mark J. Donovan

Tile Subfloor preparation is critical for a quality ceramic tile installation job. In general, tile Subfloor preparation includes insuring a stable and level subfloor that is free from dirt, dust and any type of chemicals that could prevent proper bonding between the ceramic tile and the subfloor.

Tiling over Concrete Subfloor

In general a cement or concrete subfloor is the best surface for installing ceramic tile. However, the concrete floor needs to be flat and level and free from any type of chemicals that could prevent a proper bonding between the ceramic tile and the concrete surface. If there are any paints or sealers on the concrete it needs to be removed. There are floor strippers, floor scrapers and abrasive scouring agents that you can purchase from any home improvement store to help aid in this process.

Also, if the concrete floor is new, the installation of ceramic tile should be delayed for 1 month to allow full curing of the concrete. The moisture levels in concrete must be low (below 16%) for proper bonding of tile. If chemicals were used in the curing process of the concrete then the concrete may be unsuitable for directly applying ceramic tiles.

If the concrete floor is not level or a chemical was used in the curing process you may need to apply a leveling agent to the concrete floor. You can test the concrete for chemical additives by dropping a few drops of water on the concrete. If it pools up and does not absorb into the concrete then a chemical was more than likely used. Talk with your local ceramic tile dealer to determine what leveling agent is most appropriate for the ceramic tile job.

Finally, if the concrete floor is extremely smooth you may need to rough it up with an abrasive scouring material to ensure a solid bond between the ceramic tile and concrete floor.

Tiling over Wood Subfloor

Tiling directly over a wood subfloor is usually inadequate. Typically a house has only a ¾” layer of tongue and groove plywood as the sublayer. For proper ceramic tile installation you should first add at least another ½” layer of exterior grade plywood on top of the subfloor. The plywood should be screwed or nailed down every 6-8” throughout the entire surface area of the subfloor.

Luan, interior grade plywood, OSB, should not be used as the additional sublayer material.

If there are already sufficient layers of subfloor wood material, make sure the subfloor is level. If it is not, use a leveling agent to level out the area.

About the Author: Over the past 20+ years Mark Donovan has been involved with building homes and additions to homes. His projects have included: building a vacation home, building additions and garages on to existing homes, and finishing unfinished homes. For more home improvement information visit http://www.homeadditionplus.com/ and http://www.homeaddition.blogspot.com/