Porcelain, ceramic, and stone tile can be installed in bathtub surrounds with dramatic results. This section details the most popular methods today.
In Figure C, we see a stone or ceramic tile tub surround over a prefabricated tub. In this case, a mortar bed is installed to support the wall tile. The mortar bed construction is the same for this installation as in figure B in the section on "Walls".
The tub can be made out of fiberglass, steel, or cast iron. The tub is installed level and square to the walls and should be supported by metal or wood hangers. The framing surrounding the tub should not exceed 1/2″ wider than the length of the tub.
After the tub is installed, the wall membrane and reinforcing is attached using one of the methods described in the section on "Walls". (Figure A in "Walls" for a tub installed below drywall and Figure B for a tub installed against wood or metal studs.)
Figure A in "Wall" works out very nicely if the tub has been installed below dry wall. Especially in fire rated areas where the dry wall is part of a fire rated system.
Generally, the tile will extend past the edge of the tub one full tile including the necessary trim.
Tile and trim can be installed using a trowel-able paste made from Portland cement mortar on a non-cured bed or dry set/latex modified Portland cement mortar on a cured bed.
In Figure D, we see a stone or ceramic tile tub surround using backer board as the substrate for the tile. The backer board walls are constructed with the same requirements as noted in Figure C. The only difference is that the backer board and tile will abut the tub.
Note the use of furring behind the membrane against the wood or metal studs. This practice ensures that the backerboard will be "on-plane" when it meets the tub. If the chosen tub has no upper flange, the furring is unnecessary.
If a water-resistant membrane is required for the chosen backer board, it should extend down the wall and over the tub flange. To make the installation more resistant to water related problems, install a bead of flexible sealant to the tub flange prior to seating the membrane. Once the backer board is installed, the excess membrane can be trimmed.
The joint between the tub and tile should not be in excess of 1/8″ and should be filled with a flexible sealant. The sealant should be applied after the tile and grout has cured.
When installing the backer board, tile, and grout, great care must be taken to protect the tub from damage during the construction process.
Tile and trim can be set using dry set or latex modified Portland cement mortar or type 1 organic adhesive depending on the Manufacturers instructions.
In Figure E, we see a ceramic or stone tile tub surround utilizing water resistant gypsum board as the substrate for the tile. Obviously, the gypsum board takes the place of the mortar bed or backerboard in the previous illustrations and text. Insure that the tub is properly installed. It should be square in the opening and supported by wood blocking or similar hardware per the Manufacturers instructions.
The caution with this method is that gypsum board of any type is susceptible to failure when water is allowed to penetrate the gypsum board core.
Per ANSI AN-188.8.131.52, gypsum board should not be used in "critical exposure" areas. "Critical exposure" areas are defined as ceilings in "wet" areas, exteriors, showers, saunas, or steam rooms.
It is imperative that the studs be installed square, plumb, and on plane with the prefabricated tub of cast iron, steel, or fiberglass. The framed opening for the tub should not exceed ½" larger in total width. The stud spacing should not exceed 16″ O.C. Install fireproofing behind the tub below the flange if required.
Note the use of furring behind the gypsum board. As in the case of backerboard, the use of furring is necessary if a substantial difference in plane will result when the board overlaps a flange.
Caution should be exercised to protect the tub surface during the construction process.
A membrane should not
be used behind the water resistant gypsum board. All holes and exposed gypsum should be sealed with adhesive or manufacturer recommended sealer prior to tile application.
The ½" minimum thickness gypsum board should be installed horizontally so that the factory applied paper edge meets the tub flange. The edge of the gypsum board should be ¼" from the top of the tub flange.
The point here is the gypsum board should not be in a position to sit in accumulated water if water penetrates the sealant joint between tile and tub.
The 90° joints should receive tape and a bedding coat of compound only, no finish coats. The fasteners, whether nail or screw, should receive two coats of compound.
Tile can be installed with type 1 organic adhesive or latex modified thinset mortar. The tile can be grouted with Portland cement grout or its equivalent. 90° joints and joints at dissimilar surfaces should receive a flexible sealant joint, not hard grout. This is imperative at the 1/8″ joint where the tile meets the tub, flexible non-mildew sealant only.
Choose the best quality tile and or grout sealer that the budget will allow and install the product per the Manufacturers instructions.
In Figure F, we see a tiled tub or "roman" tub installation. The illustrations represent the detail for fountains and curbs (Shower dam) also. Noted in the drawings are two types of substrates. One is a concrete shell and the other has wood framing. The concrete shell detail would be suitable for fountains in exterior locations.
As always, local, state, and federal building codes for this type of installation should be followed. Some local building codes may require additional elements than listed here.
If the concrete tank is chosen, the concrete will need to have a rating of at least 2000- psi. Basically the concrete tank takes the place of wood framing in the other half of the illustration. The wood framed detail requires a very stable and well-supported design that will resist deflection. Note the 3/4″ exterior grade plywood and doubled up framing members. Also, the framing members should be of pressure treated lumber. The idea here is that the wood framing will need to be able to support a tub filled with water that is quite heavy by volume.
Both the concrete tank and the wood framed tank will require the same two piece drain, waterproofing, and reinforcement that were noted in the shower pan detail. Except for the added framing and necessary supporting, the roman tub is constructed in a very similar way to that of tiled shower pans. Incidentally, there are two piece shower drains that have the ability to be shut off allowing the tub to be filled.
For both the concrete and wood framed roman tubs, only the method described in Figure B in the "Walls" section should be used. That is, that for the tub itself, the membrane, reinforcement, scratch, brown coat, tile and grout should be used. For walls above the tub, the methods described in Figure A or B in the "Walls" section could be used.
As in shower pans, the membrane can not be punctured inside the tank or at a level below 1″ above curb or dam height. Therefore, the reinforcement will need to be formed to fit tightly to the membrane without puncture. The weep holes are to remain clear also.
An added element in the roman tub is that the inside corners should have a cove or 45° treatment. This is a detail that allows a sanitary tub through easier cleaning. It also means that the 45° corners inside the tub will be present in the mortar bed as the use of grout or thin set mortars are not acceptable for this purpose.
If the design calls for the application of Jacuzzi jets or other below water line fixtures, Manufacturers instructions and qualified installers will need to be involved in the project.
Tile can be installed using a trowelable paste made from Portland cement and water on a non-cured bed or dry set/latex modified Portland cement mortar on a cured bed. When using latex modified mortar, the required curing time prior to grouting and use may vary. Consult the Manufacturers instructions and follow them carefully.
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