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Ceramic tile on concrete, antique floor in Buenos Aires, Argentina (C) Daniel Friedman Guide to Installing Tile over Concrete Slab Floors

  • FLOOR TILE INSTALL on CONCRETE - CONTENTS: How to Ceramic or Stone Tile Over Concrete Slabs. Using floor leveling compounds when installing tile. Guide to Moisture and Water Barriers for Kitchen or Bath Tile. Moisture Barriers for Kitchen or Bath Tile. Tile Membranes for Wet Areas, Bathrooms, Showers. Expansion Joint Requirements in Tile Surfaces. Using Isolation Membranes to Avoid Cracks in Tile Surfaces.
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How to install ceramic tile over a concrete slab:

This article discusses and compares the properties of ceramic floor tile, granite tile, marble tile, natural stone and agglomerate floor tiles. We address the installation details for each of these tile types.

This article series discusses current best design practices for kitchens and bathrooms, including layout, clearances, work space, and accessible kitchen and bathroom layout, clearances, turning space, grab bars, controls, etc.



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Guide to Installing Tile Over Concrete Slabs

Antique ceramic tile on concrete (C) D FriedmanTiles can be applied directly to a clean, smooth concrete slab with a latex Portland cement mortar. The concrete should be properly cured, be level to 1/4 inch in 10 feet, and have a steel trowel or fine broom finish.

Curing compounds or old adhesives used for carpeting or resilient flooring will act as bond breakers, so they need to be removed before installing the tile.

[Click to enlarge any image]

Either a power-blast cleaning machine or a rotary sander with a coarse carborundum sanding sheet can be used. If the slab has cracks or control joints, a crack isolation membrane should be used (see Tile Isolation Membranes).

Our page top photo illustrates ceramic tiles set on conrete in an antique floor we observed in Buenos Aires, Argentina. At left is another ceramic tile on concrete installation in the same city, with some interesting repairs. This floor was installed around 1920.

We include advice on choosing and installing kitchen countertops, cabinets, and kitchen or bathroom flooring, sinks, and other plumbing fixtures and fixture controls such as faucets. A list of kitchen and bath product manufactures and sources is included. This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons.

Other Tile Substrates Used in Remodeling

Ceramic tile over old ceramic (C) D FriedmanIn remodeling, tiles can be successfully installed over existing ceramic tile, plastic laminate, or resilient flooring (except the cushioned type) that is well bonded. These must be stripped of any sealers or waxes and scarified with a coarse sander before applying the new adhesive. Wood floors must first be covered with plywood or a cementitious backerboard.

Unsuitable substrates that should not be used under tile include oriented-strand board (OSB), lower grades of plywood with voids, and interior grade plywoods such as lauan.

The ceramic tile floors shown at left were installed atop of an existing ceramic tile floor (lower right) and over both concrete and solid core plywood (the upper floor level). The curved floor edge trim and facing were site-built by the editor (DF).

Guide to Using Floor Leveling Compounds For Setting Tile

If a wood floor or slab needs leveling, you can use special cement leveling compounds formulated for use as a substrate for ceramic tile or stone tile. These are either site-mixed from a bag or installed by a specialty subcontractor. Some are self-leveling and others require screeding.

Gypsum-based underlayments are generally not suitable for tile. Most self-leveling compounds can be installed up to about an inch thick. For thicker applications, let the first layer dry before adding more, or fill lower areas with plywood shims before adding the compound. Use exterior-grade plywood with no voids.

Guide to Moisture and Water Barriers for Kitchen or Bath Tile

Mexican quarry tile installation outside, San Miguel de Allende (C) D FriedmanAlthough glazed ceramic tile is waterproof, neither the grout joints nor the cement backerboard behind the tile are water barriers. To prevent moisture from passing through the tile and substrate to the plywood or wood framing, a moisture barrier is required in areas subject to high moisture levels or occasional wetting, such as tub surrounds and kitchen counters.

In areas subject to heavy wetting, such as shower pans and some bathroom floors and counters, a sheet membrane or trowel-on membrane should be used to provide full waterproofing.

The tile job shown at left is discussed at FLOOR TILE SEALERS, CERAMIC, STONE. We needed to seal this concrete roof as part of the tile floor installation in order to stop leaks into the room below.

In 2015 this roof tile job had its tenth birthday of years with no leaks through this floor into the space below.

Moisture Barriers for Kitchen or Bath Tile

On tiled walls, protect the wood framing from water intrusion, using either 6-mil poly or 15-pound asphalt-impregnated felt lapped to shed water. The barrier should go between the tile substrate and the framing. On outside walls, this material can also served as the air and vapor barrier if the joints are sealed with tape or a compatible sealant.

Tile Membranes for Wet Areas, Bathrooms, Showers

Figure 6-36: Installing Tile over Concrete (C)  J Wiley S BlissFull waterproofing is required in construction that must retain water, such as shower pans and tiled tubs. It is also recommended in areas subject to frequent wetting, such as raised tub surrounds, bathroom floors, and counters with sinks. There are two types of membranes: thermoplastic sheet materials and trowel-on membranes.

Sheet membranes can be applied to most tile substrates with either thinset mortar or a proprietary adhesive, and tiles are bonded directly to the membrane. With any membrane, check the label for compatibility with the substrate and adhesives. Most waterproofing membranes also serve as isolation membranes.

Figure 6-36 - elastomeric adhesive sheet membrane used below tile in wet areas.

[Click any image or table to see an enlarged version with additional detail, commentary & source citation.]

Expansion Joint Requirements in Tile Surfaces

Tile and grout are fairly unforgiving of movement in the substrate. To protect against cracking of the tile or grout joints, expansion joints are recommended by the Tile Council of America in the following places:

Expansion joints should be at least 1/4 inch wide and free of grout, backerboard, or tile adhesive. Use an elastomeric caulk with a backer rod or bond-breaker tape to prevent three-sided bonding of the caulk (Figure 6-37 below). Most tile suppliers now carry colored caulks designed to match standard grout colors, or colored caulks can be ordered from Color Caulk (see Kitchen & Bath Associations, Product Sources).

Figure 6-36: Installing Tile over Concrete (C)  J Wiley S Bliss

[Click any image or table to see an enlarged version with additional detail, commentary & source citation.]

Guide to Using Isolation Membranes to Avoid Cracks in Tile Surfaces

Polymer-modified thinset can absorb small amounts of movement, but where more significant movement is expected, a crack isolation membrane is the safest approach. Examples include tiling over concrete with control joints or shrinkage cracks, over radiant slabs, or over existing tile or other problematic remodeling surfaces. Wood-framed floors with long joist spans of 16 feet or more are also good candidates for isolation membranes.

Tile contractors typically use the same type of elastomeric membrane used for waterproofing, such as Noble- Seal TS (Noble Company) or Dal-Seal TS (Dal Tile). It is applied as described above under “Membranes” (previous page), although joints between sheets do not need to be solvent welded unless waterproofing is also required.

Methods for Slab Crack Isolation When Installing Tile Surfaces

In repair work or other jobs where covering an entire floor with isolation membrane is not feasible, a strip of membrane can be installed over just a crack, change of materials, or control joint where minor movement is expected. In general, this will work where cracks are less than 1/8 inch wide, and there is no vertical movement.

Also, with some types of membrane, the contractor can offset the sealant-filled “soft joints” in the tile, so they do not have to fall directly over the crack or control joint in a concrete slab. In this case, create soft joints on both sides of the crack or joint (Figure 6-38), using a flexible sealant instead of grout. If a crack in the concrete substrate runs diagonal to the grout joints, the soft joint must run in a zigzag pattern on each side of the crack.

Figure 6-36: Installing Tile over Concrete (C)  J Wiley S Bliss

Figure 6-38

[Click any image or table to see an enlarged version with additional detail, commentary & source citation.]

According to tile expert Michael Byrne, crack-isolation membranes used this way should be three times the width of the tile, but he cautions that the preferred approach is to cover the entire floor with membrane.

This provides better protection against cracking and eliminates the soft joints and the slight bump in the tile surface, which may be unacceptable visually.

Ceramic Tile-Setting Material Manufacturer List

Ceramic Tile Backerboard Producers

-- Adapted with permission from Best Practices Guide to Residential Construction.

Ceramic Tile Articles

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Continue reading at FLOOR TILE SEALERS, CERAMIC, STONE or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see BATH & KITCHEN DESIGN GUIDE - home

Or see WALL, CERAMIC TILE INSTALLATION for an illustration of installling ceramic tile on a concrete wall

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