Ceramic, porcelain, and stone tile can successfully be installed on all manner of countertops. Selecting the right backing beneath the tile is very important. The following section will give the reader some of the most popular methods used in building the countertops of today.
Before getting into the various methods, take a look at the following paragraph concerning the selection of the types of sinks involved in countertop installations. Not all countertops will involve a selection of a sink type. For the countertops that do, sink selection may play a major role in the method chosen. For tile in sinks, for example, the only recommended method is the mortar bed which allows the installer to recess the sink at or below tile height.
Two types of sinks for kitchens and bathrooms are available. One type is the "tile in" type which is set below or in line with the tile surface. The other is a "self rimming" type which rests on top of the tile. This is an important consideration. While the "self rimming" type is a little easier to install, it is more difficult to live with due to its difficulty when cleaning. When the countertop is wiped off, water and debris collects at the edge of the sink due to its elevated lip.
How the tile will be set, the trim used, and any accents will depend on design preferences and what field tile was selected. Since countertops tends to be the focal view of the room they occupy, field tile, trim, and accents should be selected to give the best appearance possible. Tile for the deck needs to be able to be installed on plane. Meaning the tile needs to be as consistent in thickness as possible.
Tile Doctor Tip: Industry standards for finished tilework is that it be level and on the required plane and no variations exceeding 1/4″ in 10 feet. No excess lippage be present and the range is from 1/32″ to 1/16″ depending on the tile size, characteristics, and joint width. Lippage is defined as the difference in height tile to tile.
There are elements in the countertop tiling process that is consistent regardless of the substrate. The first is that the cabinet or shelf be level and flat within 1/8″ in 10 feet. This is especially important when the substrate for tile is backer board or plywood. The other is that the countertop height has sufficient clearance for any necessary appliance like dishwashers and trash compactors. The height should be calculated measuring from the finished floor height to the bottom of the countertop trim.
Another consistent element is the structural integrity of the cabinet or wall mounted shelf. The strength of the tiled installation is dependent on its base. Cabinets need to be securely fastened to the wall and sometimes the floor to provide adequate support and resistance against movement. Shelves should not only be securely fastened to the wall, they also need to have adequate support like brackets to support the weight of the tile installation and subsequent weight of items placed on their surface.
Prior to beginning a tile installation, carefully check that the cabinets or shelves have been installed straight and level and all fastening devices are adequate. Also, make sure that any 90 degree corners are square to one another. Look under the cabinets to insure that they are not resting on any removable items like shims or flooring material. If shims have been used to level the cabinets, make sure they will not be removed by anyone after the tiling has begun. If the shims are removed after tiling has begun, the cabinets will settle possibly causing the tile work to crack and fail. Let's look at the three types of countertop installations popular today.
In Figure A, we see a mortar bed deck and mortar bed wall installation. This installation can be applied over cabinets or wall mounted shelves. The base for the mortar bed can be 1″ X 6″ boards spaced 1/4″ apart or exterior grade plywood sheet.
If the base is plywood, random dot and dash saw cuts 6″-8″ parallel to the cabinet edge need to be made. The 1/4″ spacing or saw cuts are designed to allow the wood to equalize moisture content. If moisture does not equalize in the boards, the boards can buckle and warp causing the tile above to fracture. Normally in the mortar bed countertop method, the backsplash consists of a solidly backed wall. Meaning that the back wall in these cases is normally drywall, masonry or plaster. This means that a one-coat mortar method can be used on the back wall. Refer to the "walls" section in The Tile Doctor for this method.
Once the wood base has been satisfactorily prepared, the membrane should be installed. The membrane should be 15 pound roofing felt, reinforced asphalt paper, or 4 mil. Polyethylene-sheeting. The membrane should be continuous over all exposed wood surfaces. The continuous feature of the membrane means that the membrane should overlap the front edge of the wood base and extend down into any openings like the sink or range. All seams in the membrane should overlap at least 6″ and the membrane should be carefully folded and tucked into all corners.
The membrane can be tacked into place using corrosion resistance staples. While the membrane is installed, apply "Kraft" type paper or polyethylene sheeting to the face of the cabinets to prevent any damage to the cabinet face during the tiling process especially if the cabinets are unfinished. It is best if the cabinets have already received their final finish prior to beginning the tile work. If the choice is to use a self-rimming sink, omit the following step of installing the "tile in" sink. The "tile in" sink should be installed after the membrane and can be installed prior to or after the reinforcing wire. Some installers prefer to install the sink into a bed of fresh mortar. These installers then level the sink with mortar.
Others prefer to place the sink on top of the membrane and shim to level using corrosion resistant metal or doubled up reinforcing wire. Deck mortar is then forced into the joint during the mortar bed application. Whichever method is chosen, the sink must be a close to perfectly level as possible. When tiling in a sink, the appearance of the tile trim around the sink depends of this procedure.
In a common installation of a kitchen sink with v-cap trim, the sink needs to be positioned from the counter edge to allow enough room for the cap strip, v-cap tile trim, 1/8″ of bonding mortar, and quarter round trim. With 24″ cabinets, the rear of popular kitchen sink sizes will be within 1/2″ of the backsplash allowing just enough room for quarter round trim. Make sure that these measurements are checked during the layout and preparation phase.
If the "tile in" sink is to be flush with the tile surface, the same leveling procedure must be accomplished. However, the sink height will need to be approximately 1/4″ above the mortar bed. If the sink is to be trimmed with surface bull nose tile, the sink will need to be even in height to the mortar bed. The height requirements are a factor in the next step. Once the sink is in place, it should be protected with a combination of duct tape and "Kraft" or roofing felt paper. The protection should be adequate to prevent damage. However, it should not be installed too thick as to interfere with the following steps.
After the sink is in place and protected, the punched metal strip or "cap strip" is installed. For "tile in" sinks that will receive quarter round trim, the mortar bed needs to extend above the level of the sink 1/2″ for proper placement of the quarter round trim. This allows space for the trim and a 1/8″ gap between the trim and sink to be filled later by a silicon sealant. Hard grout should not be used in this joint.
Tile Doctor Tip: In some geographical areas, cap strip is not used. Instead a wood form is used in place of the cap strip and is installed in the same manner. After the deck mortar cures, the wood form is removed exposing the deck mortar and other elements for the trim tile to be bonded to. Hence forth, the use of cap strip has the same meaning as wood form.
To set the cap strip use a 1/2″ thick float strip placed on the rear edge of the sink. In this way, a level can be placed on the float strip and used to set the height of the cap strip.
The cap strip must then be leveled across the face of the counter. This will take some adjustment so use a screw to secure the cap strip. Remember that the cap strip needs to be as perfectly level across the face of the counter as possible. Cap strip should be used in the longest lengths possible for added strength. They are normally found in 5′ lengths. The first cap strip should be centered on the sink unless there is a 90 degree corner immediately to the right or left. In this case the cap strip should be tucked in to that corner being careful to allow room for adjustment.
Once the first cap strip is in place, the rest of the strips are placed with caution used to keep the strips level one to another. Unless the wire reinforcement has already been accomplished, it should be installed in the next step.
If there are to be openings in the deck surface for countertop ranges or other appliances, leave the membrane continuous over the opening. However, carefully mark the opening during the membrane installation and terminate the wire reinforcing at the edge of the opening. This will allow the wall mortar to be placed without falling through the opening. After the deck is completed, the membrane can be cut away leaving the appropriate sized opening.
Expanded wire lath weighing not less than 2.5 pounds per square yard is used for the reinforcing of both the deck and backsplash. It must overlap at any seams at least 2″. It should extend from the inside edge of the cap strip and terminate at the point where the backsplash mortar and tile will meet the deck mortar. The idea here is to eliminate cracking of the backsplash and deck tile at the 90 degree corner. The reinforcing should be fastened to the base with corrosion resistant staples or nails capable of catching three strands of wire.
The fasteners should be spaced in a grid pattern 6″-8″on center. Care should be exercised not to puncture the membrane in an unsupported spot. The backsplash reinforcing should be attached in a similar manner terminating the lath at the bottom where the deck tile and backsplash will meet. The next step is floating the wall mortar. Follow the steps for the one coat method outlined in the section of The Tile Doctor on "walls." Allow the backsplash mortar to cure for 24 hours prior to moving on to the deck mortar. This forms a "cold joint" between the deck and wall mortar further preventing the chance of a cracked backsplash after the tile is installed. The cap strip front and rear and the area around the sink or any openings should be backed up and filled with wall mortar. The deck mortar will not be suitable for this process. Use a finish trowel and margin trowel for this application. Cut the wall mortar in a 45 degree angle down to the deck as shown in the photographs. This allows the deck mortar to meet the cap strip mortar in a more monolithic structure.
Note: It is the practice of some installers to fill the front of the cap strip after the deck has been floated.
Following the wall float and cap strip filling, the next step is applying the deck mortar, which is sometimes called "dry pack." Dry pack is a useful term as it denotes a very dry mortar. The more water that is present in the deck mortar means that more water will have to evaporate leading to shrinkage. Too much water can also lead to a less water resistant mortar bed. The proper mortar mix for decks is 1 part Portland cement to 5 parts damp sand. Plasterers sand works best for both walls and decks. The sand needs to conform to ASTM C 144. Nevertheless, mix the cement and sand first then add water. The properly prepared mortar should have enough water to clump together when compressed in the hand. After clumping the hand should almost appear dry.
That is not very much water! An initial coat of deck mortar is installed and tightly compacted into the reinforcing wire in all areas. An attempt should be made to fully imbed the reinforcing leading to more corrosion resistant reinforcing. Skilled craftsman can fully place the deck mortar at this time and float the deck using a combination of a level and wood float. The procedure is to use the level to establish level furrows at strategic places on the deck using the installed cap strip as a front form. The installers then use the level to cut off excess mortar as they move along the deck keeping the mortar level. Voids and imperfections are filled as they go with the wood float.
This method eliminates the need for float strips in the deck mortar thus saving time. For the novice, this method may not be the best choice. For the novice, a column of deck mortar is raised toward the rear of the deck for the installation of the float strip. Float strips are commonly 1/4″ redwood lath that are temporarily imbedded in the deck mortar and are removed after the deck mortar has been floated. The recesses left when the strips are removed are filled while the mortar is still plastic or not fully cured. Float strips can be placed from the front to rear of the deck allowing the installer to cut the deck mortar off the bed from front to rear.
Another method is to use a 1/2″ thick float strip on top of the "tile in" sink and cut off the excess mortar from left to right. The 1/2″ thickness allows the perfect height for the deck mortar above the sink surface which is the perfect height for the later installation of the sink quarter round trim. The instructions for this method follows this paragraph.
The float strips are cut to the appropriate length for each part of the deck and soaked in water prior to placement. The pre-soaking makes the strips easier to adjust, as they tend not to absorb too much water from the mortar. The float strips should be cut to meet the cap strip and extend to the necessary part of the deck. The float strips are designed to allow the installer to pack the deck mortar in place then cut off the excess. Locate the float strip toward the rear of the sink. The column of deck mortar will terminate at either end of the sink. Remember that the 1/2″ thickness of the float strip is the ultimate height of the deck mortar. The float strip needs to rest directly on the sink top for a successful installation. The float strip must be carefully leveled in every direction. A special concern exists for "large" expanses of countertop space or where the countertop has any weak areas of support. A "large" area would be any countertop area 3′ or longer in length. These areas need extra support. This extra support can be accomplished with 1/4″ pencil rod formed into flat "s" shapes and imbedded into the approximate center of the deck mortar.
Another area of concern is the front of the sink especially in modern designed cabinets with pullouts for sponges and implements. If it is possible to push down on the cabinet face in front of the sink and there is any movement, the area needs to be reinforced with pencil rod in a similar fashion as above. However the shape desired would be a squared off "c" shape. Again the reinforcing 1/4″ pencil rod in the middle of the reinforcing bed is used.
Once the float strips are in place, the deck mortar is trowelled and tightly packed onto the deck using a combination of wood or steel trowel and margin trowel. The surface of the mortar is brought up by eye to the level of the float strips and excess mortar is cut off using a steel or wood screed. All depressions and holes should be filled and any high spots eliminated. Care should be taken to pack the mortar tightly up to and just over the edge of the sink. Once the deck mortar has been installed, the float strips are removed and filled with mortar. To remove the strips, cut along each edge of the strip with a margin trowel being careful not to dig out the adjacent mortar. Next, pry the float strip out with the margin trowel from one end to the other loosening it as you go. Carefully fill the recesses with mortar using a combination of finish trowel and margin trowel. Cut off the filled recesses flush with the deck using the finish trowel. Tile can be installed immediately using a trowelable paste made from Portland cement and water. Commonly the deck is allowed to cure for at least 20 hours at 70 degrees F or longer and tiled using Portland cement thin set mortars. Check the Manufacturers instructions for the bond coat requirements that will be used.
In Figure B, we see a plywood countertop method. This method should be used in interiors only and not in heavy use areas where moisture is commonly present. The same precautions apply to this method related to cabinetry and adequately installed and supported shelving. Like the method illustrated in Figure B, tile will be installed directly to the plywood. This means that the base needs to be nearly perfect in terms of level and on plane. Any fluctuations in plane or level will be evident in the finished tile work. Out of level will be immediately evident in the backsplash tile, which will be set on top of the deck. The same requirements exist related to proper height for dishwashers and appliances measured from the finished floor height to the bottom of the countertop trim.
If this method is chosen for a kitchen countertop, a self-rimming sink is generally the only choice. The self-rimming sink is installed on a bed of sealant, which can impart a water-resistant joint between the tile and sink. The danger is that water can infiltrate the joint and be absorbed into the plywood eventually leading to failure. The plywood should be 19/32″ to ;3/4″ exterior grade and needs to be fastened securely to the base structure. Note from the illustration that the plywood was fastened to a wood base that is fastened to the cabinetry. This step may be necessary to allow the proper finished height for the tile work. The plywood should be treated to resist exposure to water and or high humidity.
Corrosion resistant ring shank nails or screws capable of fully penetrating the plywood and base need to be used. Epoxy (described under ANSI 108.6), organic adhesive (described under ANSI 108.4), or certain types of Portland cement mortars can be used to install tile and trim. The Manufacturers instructions for these adhesives must be followed closely. If the choice for adhesive is epoxy, leave 1/4″ gaps in plywood joints to be completely filled with epoxy during the tile setting phase. A batten should be applied beneath the plywood to prevent the epoxy from running out of the joint into the cabinetry below.
In Figure C, we see a backer board countertop installation. In many ways this method is similar to Figure B. This is especially true in the requirement for the surface to be level and on plane. The cabinetry or shelves must be adequately supported and level to within 1/8″ in 10 feet. This method is more water resistant and durable than a plywood installation. Generally, the sink chosen for this method should be a self-rimming type. This is due to the difficulty presented in recessing the sink allowing the appropriate trim to be used. Efforts have been made by some installers to notch out the backer board allowing the sink to be recessed enough to allow surface trim to be used. However, the problem of sink movement and adequate water resistance causes concern. This type of installation is not impossible; it should just be approached with great care.
Make sure that the Manufacturer recommends the chosen backer board for countertop use. At a minimum, the backer board chosen should be in the 1/2″ thick range. The normal score and snap method is acceptable for countertop use. However, some backer boards will not score and snap well for the countertop face that will support the front of the trim or "v-cap." This requires lengths of backer board only 2″ wide. Some backer boards will break and crumble in this small width. In this case, it is better to use a dry cut off saw to make these cuts. Nevertheless, the process starts out with the base of 3/4″ exterior grade plywood securely fastened to the cabinetry of shelf. The dot and dash cuts mentioned in Figure A are again necessary especially for kitchen installations where the equalization of moisture is necessary.
This is the area that gets a little complicated. Backerboards should have a bed of freshly combed thinset beneath them. A countertop is similar in this respect to backerboards installed on flooring. The thinset bed insures that no air pockets remain between the board and the plywood.
Some manufacturers recommend that a waterproof membrane be installed over their backerboard. Still others recommend that it be installed between the plywood and backerboard. Some others have no recommendation. The issue is that recent changes, according to the Tile Council of America 2009 Handbook, indicate the need for a water resistant membrane in countertop installations. If a typical membrane like 15lb roofing felt were used, the felt would interrupt the advantage of the thinset layer. Hence, it might be a good idea to use a liquid applied membrane if one was to be installed under the backerboard. Again, follow the manufacturer's recommendations.
The backer board should then be installed over the base using 1-1/4″ minimum corrosion resistant ring shank nails or screws recommended by the Manufacturer. The fasteners should be spaced 6″ on center. 1/8″ to 1/4″ gaps should be left at the backer board joints to be filled with latex modified Portland cement mortar then taped with alkali resistant backer board tape when required by the Manufacturer. Some backer board Manufacturers require that their unit be butted directly. Once the deck backer boards are in place, the front edge backer board is installed. For this step, the width of backer board will depend on the countertop edge trim chosen. This edge piece is nailed or screwed into the plywood at 6″ on center. This joint then needs to be covered with three layers of alkali resistant mesh tape. The required latex modified Portland cement thin set is applied to the tape during the setting of the trim.
At this point, the backsplash backer board is installed. The backer board can be nailed or screwed into place using the appropriate fasteners or set in a trowelled coat of latex modified thin set. The addition of the thin set is helpful to level the backer board panels and to provide full support. Use a mallet and beating block to firmly seat the panels being careful to keep the panels straight along the length of the wall. Once the panels are in place, the same taping procedure for the backer board joints is necessary if required by the Manufacturer. Tile can be set using latex modified Portland cement mortar and grouting can be accomplished using latex modified Portland cement grouts or epoxy grouts.