This “how to” section will detail the application of stone tile or ceramic tile on interior floors. Click here for tile on concrete slab, look in the archived interior tile floor section using the archive link above.
In the following photos, we will see an upstairs bathroom receiving a polished marble floor placed over backerboard. The ½” backerboard used for this project was manufactured by Custom Building Products as well as the thinset mortar, grout, fasteners and joint tape.
Here we see what the bathroom looked like with the original carpet flooring. The carpet was above an OSB sub-floor with joists spaced 16” on center based upon examinations of the ceiling in the room below. It was therefore suitable for the intended backerboard project and ceramic tile.
First, the baseboards are removed by scoring the paint with a utility knife then prying the baseboard off with a pry bar.
Next the carpet is cut where the tile and carpet will eventually meet. Generally in doorways, the ceramic tile and carpet will meet in the middle of the door so that the joint cannot be seen when the door is closed. In an archway such as this, the joint will be in the approximate middle of the floor directly beneath the arch.Carefully peel back the carpet exposing the padding and tack strip next to the perimeter walls.
Remove the padding and tack strip from the floor area. The tack strip is removed with a pry-bar and the padding simply by pulling it loose. In this case, the padding was only stapled to the wood sub-floor. The staples were removed with a pair of pliers. If the padding had been glued down, it would have been necessary to scrape the glue and padding remnant with a scraping tool. The point here is to make the wood sub-floor as flat as possible.
Once the padding and tack strip has been removed, the floor is closely examined its on-plane requirements (1/4” in 10 feet) and any protrusions that would adversely affect the placement of backerboard panels on the sub-floor surface.
The sub-floor was sound and on plane and it was only necessary to re-drive the floor fasteners that were not driven flush with the floor surface by the original trades. These fasteners, with square head drives, were driven flush prior to proceeding with the backerboard installation.
Next the doorjamb trim was cut which will allow the backerboard and tile to slip under the wood trim easing the installation and creating a more professional appearance. This was accomplished using a tile intended for use and a scrap piece of 5/8” drywall below the tile. The extra 1/8” proved to be a perfect additional height allowing room for the layer of thinset below the backerboard and the thinset setting bed for the tile.
Next measurements were taken and the backerboard was cut to fit into the floor areas allowing 1/8”-1/4” gaps between sheets and ¼” at all perimeter joints. The backerboard was arranged perpendicular to the sub-floor making the backerboard parallel to the flooring joists. Backerboard joints should be staggered so four corners do not meet together.
Backerboard can be cut by the “score and snap” method or by dry saw. The dry cut off saw works very well with fiberglass encased cementitious board like this one.
For cutting the toilet receptor hole, the drill and punch method works well or in this case a hand grinder with a dry cut off blade was more than adequate.
Once all the panels are cut and properly fitted onto the sub-floor, the panels are lifted up and a bed of dry or latex modified thinset is placed onto the sub floor.
The thinset is “keyed in” using the flat side of the trowel then combed out to a consistent depth using the notched side. In this case a ¼” X 3/8” rounded notched trowel was used at a 45° angle to assure that the panel came to rest on the sub-floor fully supported on its entire underside.
Next the panel is beaten in with a mallet and beating block. Note how the panels are staggered not allowing four corners to meet at one spot.
Next the panels are screwed down on 6”-8” centers along the perimeter and in the field with the recommended 1 ¼” screws. The screws should not come closer than 2” to the edge of the board. Be sure to drive the screws flush with the panel surface. However, use caution to not overdrive the screw as the strength in this type of board is at the surface mesh.
The process of fastening the boards continues till the last panel is adhered and screwed.
The Manufacturer of this backerboard requires the filling of the backerboard joints during the tiling process with the same setting mortar used to set the tiles. The Manufacturer does not require the filling and taping of the joints with mesh tape as other backerboard Manufacturers do.
The filling and taping of joints is an extra precaution used in this job and may well be over building. The result is a more monolithic floor. The procedure is to fill the joint, imbed the alkali resistant tape, and smooth the joint with thinset feathering it out over the joint.
The procedure of filling and taping the joints does require that the joints have time to cure before the application of tile. If it is desired to tile soon after the panels are set, then a fast setting thinset may be used in the filling and taping process to speed up the job. Be sure to check with the Manufacturer concerning the products you plan to use
Next the layout process starts. In this case it was desirous to have full tile at the entrance and at the edge of the combo shower and tub. This provided a nearly full tile across the room where the double sink cabinets were. Most of the visible cuts appeared to be full tile.
The process was simple. Full tile was laid out from the shower face and room entrance and measurements indicating the full tile placement were taken. Two working lines were established down the length of the room and one perpendicular to the first line. A framing square verified that the line were square to one another then verified with the 3-4-5 method.
Next the entire floor area was measured and grids were chalk lined in establishing where all the tiles will be set. Each “box” or grid has room for four tiles and grout joints in the center and on two sides. This is known as the grid method seen in the “estimating/layout-floors” section.
The final step once you are sure the lines are exactly where you want them is to “permanize” the lines with clear lacquer spray.
Mix the thinset according to Manufacturers instructions and have all your tools at the ready before the tiling process starts. Start at one side of the room and make the necessary cuts in advance of laying out the first thinset bed. This is especially a good idea if the cuts are intricate like around doorjambs or tub faces.
Next pick up the dry set tile and begin the tiling process by “keying in” the thinset onto the backerboard surface using the flat side of the trowel. Follow the “keying in” process by combing out the thinset to a uniform depth using the notched side held at a consistent 45°angle. Be sure to apply the thinset inside the working lines without obscuring them.
Be sure to clean the edges next to adjacent tile of excess thinset with a margin trowel to prevent too much thinset “squeeze” in the grout joints.
When the tiles are placed within the grids, always orient the tiles to the same lines in every grid. The four tiles will always meet two of the lines directly while allowing grout joint space on the other side of the grid.
To illustrate this concept let’s say the marble tile was 12” exactly and you wanted 1/16” joints. Each grid would measure 24 1/8”. This allows a 1/16” joint between the tiles and a 1/16” joint at two sides of the grid.
The final step in setting the tile is carefully beating in the tile with a beating block and rubber mallet. This will ensure the proper coverage of thinset and will minimize lippage. Be sure to beat in on the joints and the four corners where the tile meets each other. Finally realign the tiles within the grid and move ion to the next grids.
After beat in, be sure to clean the tile surface with your tile sponge and clean out any excess thinset from the grout joints. This step will save you a lot of time during the grouting process.
Because there are taped joints in the backerboard on this job, it is necessary to back butter some of the tiles to avoid excess lippage. If you notice a tile is too high or too low when placed in the field, back-butter the tile, using a margin trowel, to make up for the height difference.
Some grids will be too small to fit the notched trowel for combing and applying the thinset. In this case “key in” the thinset using a margin trowel and apply the thinset directly to the back of individual tile using the notched trowel in this manner.
The tiling process continues until the floor is completely tiled. The floor is allowed to cure according top the Manufacturers specs and the grouting process begins.
Assemble your grouting tools.
Mix the intended grout per the manufacturers specs. In the case of polished marble, non-sanded grout should be used so that the polished surface will not be scratched during the process. Mix the grout and remove the lumps by forcing the grout against the bucket side with the margin trowel until the grout is completely smooth and the consistency of a thin sour cream. Do not forget to allow the grout to stand or “slake” for fifteen minutes.
Moisten the tiles with a damp grout sponge then force the grout into the grout joints being sure to fill the joints completely leaving no voids. Cut off the excess grout using the hard rubber grout float at a 45° angle diagonally across the tiles filling the joints flush with the grout.
Use a grout sponge nearly wrung dry of water and tool the joints applying as little pressure as possible diagonally across the tile joints. The point here is to make the joint presentable without digging the grout out of the joint.
Do final wipe of the tile joints diagonally removing the excess grout. The joints should be smooth, uniform, and free from voids or pinholes.
Since non-sanded grout was used in very deep marble joints, it is sometimes necessary to refill the joints once the water leaves the original grout in the joint. The procedure is the same.
Once the joints are filled satisfactorily and any voids, pinholes, or imperfections are filled and smoothed, the curing process begins. When the surface of the tiles begins to dry and the joints begin to cure, grout haze will develop on the tile surface. This is best removed carefully at this time with the use of cheesecloth or terry cloth.
Following the Manufacturers curing of the grout a sealer was selected for the marble tile and grout. In this case a penetrating sealer from Aquamix was used.
The sealer is simply applied to the tile and grout and allowed to stand 3-5 minutes with a sponge applicator. The excess is wiped off with paper towels. The first coat is allowed to dry one hour then the process is repeated. The floor is ready for traffic the next day.
This is an alternative and very good way to seal grout joints where the sealing of the tile itself is not necessary. The apparatus applies sealer only to the joint minimizing the wasted sealer and making the paper towel clean up very easy.
Next the carpet at the two doorways is trimmed and fastened. The padding is cut back to allow room for at least one tack strip and a piece of “z” bar. Be sure that the “z” bar is at least 3/8” from the tile edge. This allows the carpet to be folded over and under the “z” bar.
The carpet is measured and carefully cut with a sharp razor knife and straight edge. The carpet needs to be ½” longer than the point at which it will meet the tile. This allows the carpet to be tucked into the “z” bar. After tucking in the carpet, pound down the carpet and “z” bar beneath, with a beating block and mallet, to lock in the carpet to the “z” bar and tack strip nails.
Next the dissimilar surface joints are filled with a sealant that matches the grout color.
The perimeter joints are left open to be covered by base molding and the job is finished.