Failed installations are costly and avoidable. Industry standards for the following installation methods and specifications are found in the current issues of the (TCA) Tile Council of America's Handbook for Ceramic Tile Installation, (ANSI) American National Standards Institute Manual, and the (MIA) Marble Institute of America's Design Manual.
Tile can be set successfully in a variety of ways and on a variety of surfaces. Including, tile to tile, paint, epoxy coatings, seamless flooring, vinyl or asphalt flooring, plywood or paneling, hardwood flooring, and steel plate.
Residential applications such as "kitchens, bathrooms, and foyers." have numerous acceptable methods listed in the TCA Manual, both for concrete slab and wood sub floors.
- Cement fiber
- Glass mesh
- Latex cement coated foam core board
Cement fiber backer units, described under ASTM C 1325, have mineral fibers within the body of the unit to give the board strength.
Glass-mesh type, described under ASTM C 1178, is aggregates and cement encased with a fiber mesh for strength.
These units are generally installed with the same method. However, it is the cement fiber units that offer greater water resistance.
All backer boards must be used over dimensionally sound framing and sub-floor. Cement backer boards do not necessarily offer greater resistance to deflection. Backer units should be adhered to the sub floor in two ways.
- Units should be applied to fresh (thinset) a bed of dry-set Portland cement mortar applied with a trowel.
- Then the units should be nailed or screwed to the sub floor with corrosion resistant fasteners. Screws and ring shank nails should pass through the units fastening them securely to the sub floor. The fasteners should be applied in a grid pattern 6" on center.
The panels should be spaced 1/8" apart. The panels should be perpendicular to the sub floor panels. The gap should be filled with the bonding mortar and taped with alkali resistant joint tape imbedded in a fresh bond coat mortar.
Cutting cement board is similar to cutting drywall. They are scored on one side with a carbide scoring tool and straight edge. Then stressing the board by bending at the point of scoring snaps the panel.
Once backer units are installed, they may be tiled using dry-set or latex Portland cement mortar and grout.
Tile over concrete: Here we see stone, ceramic or porcelain tile placed directly over a concrete slab. This would be accomplished after the slab was fully cured and prepared to receive tile. This means that any cracks were repaired and any surface contaminants removed. This is a "thin set" method.
Thinset mortars are available that maintain flexibility and can successfully take the place of a membrane in the application of ceramic porcelain, or stone tile.
Tile over wood: Here we see a stone, ceramic or porcelain tile bonded to a double plywood wood floor. This method should be used on light duty interior floors not exposed to moisture. This method can actually impart more resistance to deflection than cement backer board units.
It is recommended that the sub floor is at least 5/8" plywood or 1" nominal boards and the overlay is at least 5/8" exterior grade plywood. No particle- board should be used. The 1/8" gaps are necessary for expansion/contraction of the plywood. Be sure that no joints match the framing below and that all joints overlap the joints below by at least 2." Use foam strips, caulking or duct tape to insure that no debris or setting materials gets into the joints.
The sub floor should be securely fastened to the framing members with screws or nails. If any squeaks or movement is detected, refasten where necessary. We use corrosion resistant screws or ring shank nails to fasten the overlay to the sub floor in a grid pattern 6" on center. The screws or nails should be at least 1-1/4" long to penetrate both sheets.
This method can be used with special "EGP" type Portland cement, organic floor type 1, and epoxy adhesives. Also, the method can be used with a special "proprietary membrane" like "Schluter Ditra."
Mud Bed: This method can be used over structurally sound wood sub floors. For residential floors, a mud bed thickness of 3/4" is acceptable. For light commercial duty floors, a 1-1/4" thickness is recommended. If a thicker floor necessary, the suitable reinforcement could be 2"x2" 16/16 wire set in the middle of the mud bed for greater strength. This allows a for a mud bed up to the thickness of 2". Any mortar bed that needs to exceed 2" in thickness, should be detailed by an architect.
ANSI A-4.1a.2.2 recommends the following mortar mixing ratios for deck or floor mortar. 1 part Portland cement (common cement), to 5 parts damp sand (Needs to comply with ASTM C 144) and optionally 1/10 part hydrated lime (Needs to comply with ASTM C 206 or 207). Always try to use damp sand, your batches will tend to be a more consistent. If hand mixing, mix the dry ingredients with the damp sand first. Then add just enough water to fully moisten the mix. Good floor mortar will clump and stay together when squeezed in the hand. If machine mixing is desired, the water must be added to the mixer prior to the dry ingredients.
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