Wall Layout Before the bond coat application, walls have a special consideration due gravity. Unsupported tile set on bonding mortar can and will sag. This can be eliminated with the use of a ledger below the first row of tile. If the wall tile starts at floor level, above a shower or tub, or on a counter top the use of a ledger is not Anecessary. However, care must be taken to insure that the first row of tile is level and flat so those successive rows will remain level and flat.
A ledger can be a metal or wood straight edge applied to the wall directly below the lower working lines. In three wall tub or shower enclosures, the back wall and sidewalls can have ledgers applied to the three lower working lines. This allows the installer to tile all vertical surfaces and have the grout joints line up perfectly through all three walls. The ledgers can be held in place by temporarily screwing them to the substrate or balancing them on stacked tile. The installer only needs to be careful to make sure the ledger is aligned with the working lines. Bond Coat The bond coat must be applied to produce a minimum coverage for the item to be bonded. It is recommended that tile, when set and beat in, has coverage of mortar on the back of the tile greater that 80% in dry interior areas and 95% in wet or exterior areas. It is also recommended that the bond coat be at least 3/32" thick between the tile and setting bed. That is verified by systematically pulling up several tiles in a field of tile while the installation is in progress. This is the reason you will see various sizes of notched trowels recommended for certain sizes of tile. If the trowel size is not sufficient to provide the coverage, a larger trowel size needs to be selected. If 100% coverage is desired, tiles need to be back-buttered. Back buttering is a good practice especially if the tile has a lug back or is an out of plane shape. Back buttering is not difficult. The process is designed to even out the back of the tile prior to setting the tile and beating it in. For some tiles, this may mean only a thin "skim coat" of the bonding mortar is applied using a straight non-notched finish trowel. Other out of plane tiles may require a thicker coat. The idea, again, is to even out the back of the tile prior to setting. Dr's Tip: For tile larger than 8" a 1/4" x 1/4" notched trowel and back buttering normally leads to 100% coverage. It is best to take the time to use this procedure and eliminate the problems associated with lack of coverage. Is it possible to apply "thin set" mortars too thick? Yes it is. Portland cement "thin set" mortars cure by hydration. While they cure a certain amount of shrinkage will occur. Their bonding strength, if applied too thick, can actually fracture tile. This is the reason you will see "medium set" mortars available. Medium set mortar is manufactured for specific installation requirements. It is especially useful when setting tile on irregular setting beds and tile that varies in thickness. The procedure for applying the setting bed is simple. Without covering or disturbing the layout lines or ledger, a sufficient amount of bonding mortar is applied to the substrate using the flat side of the notched trowel first. Scoop out enough mortar to skim coat the whole surface to receive tile. A5h13Use the flat side of the trowel to push the mortar firmly into the substrate. Then apply enough mortar to comb out the desired area using the notched side at 45° to a uniform depth. Be careful to come as close to the layout lines as possible without obscuring the lines. This can be accomplished with a little practice. Once the bond coat or setting bed has been troweled, it is time to set the tile. Remember that it is a good idea to back butter tile larger than 8" or any tile where 100% coverage is desired. Set the tile in place and beat it in using a rubber mallet and beating block. For small tiles up to 6" use the beating block and mallet or just the rubber mallet for large tiles. The idea here is not to hammer the tile into place. The idea is just to firmly seat the tile into the setting bed. There is no need to exert great pressure on the tile. So "softly" beat the tiles into the bed of mortar. Once the tiles are placed and beaten in, align the tiles with your layout lines or ledger and clean off any bond coat residue from the tile surface. The bond coat should not interfere with the grout ability to penetrate the joint by at least 2/3 of the joint depth. Note: Spacers, if used, must be removed prior to grouting. At this point, the installer can apply spacers if necessary. When using spacers, do not put them into the corner joints where the four corners meet. Simply place them in the joint between the tile. They therefore stick out from the joint. Once the tile has set and the thin set has hardened the tile into place, simply brush off the spacers and re-use them. Removing spacers used in the traditional manner is difficult and the installer runs the risk of damaging the tile work in the process. If the chosen adhesive is in the epoxy or organic class, carefully follow the Manufacturers instructions for their use. A word of caution about epoxy adhesives: all residues must be removed from the face of the tile, as it is difficult to remove after it has cured. Let's talk first about Portland cement based grout since this is the most commonly used material. Once the grout is mixed per the Manufacturers instructions, it needs to be installed. ANSI recommendations for Portland cement based grouts used in tile work are described under ASNI 108.10. Be careful to allow the tiled installation to cure for the period prescribed by the adhesive Manufacturer prior to grouting. Some adhesives require longer curing time than the 24-72 hour normal Portland cement curing times. This is a good time to carefully check the tiled installation for any adhesives that were left sticking out of the joints or left on the face of the tile. Thoroughly clean and inspect the tiled installation prior to starting the grout phase. I prefer to use a razor knife to scrape excess thin set or adhesive out of the joints. For Portland cement grouts, it is a good idea to moisten the joints with water prior to applying the grout. This allows the grout to flow into the joint smoother and it prevents the tile from prematurely wicking too much water out of the grout. Do not leave puddled water in the joint prior to grouting. Check the Manufacturers instructions for the intended product for pre-moistening instructions. Apply the grout to the tiled surface using a hard rubber grout float at a 45° angle to force the grout fully into the joint. Work in a small area applying enough grout to fill the joints. Do not work too large of an area. I recommend 2-3 square feet at a time for a novice. Use the grout float diagonally across the face of the tile finishing the grout flush with the face of the tile. In affect, you are "cutting" the grout excess off the tile. The reason for working in a small area is simple. The grout will start to cure once it is applied. While it is still workable, it needs to be initially tooled into the joint. This means that the cutting off of excess and sponge finishing needs to be nearly complete before the curing begins. Dr's Tip: Remember to leave the necessary expansion joints open (like 90 degree and dissimilar surface joints), and clear of setting and grouting materials for the installation of sealant and backing material if necessary. After the grout has been "cut off" the face, the next step is sponging the surface and tooling the joint. Tiles with a square edge need to have the grout finished flush with the tiled surface. Tiles with a cushion or radius edge should have the grout finished to the bottom of the cushion or radius. This is accomplished by pulling the sponge across the face of the tile diagonally exerting just enough pressure to move the sponge. The idea is to clean the excess grout off the face of the tile and give the joint a smooth finished look. This will take a little practice and the technique can be learned quickly. Do not dig out the grout with too much sponge pressure and try to keep the sponging to a minimum. Per ANSI 108.10, the joints should be "uniform in color, smooth, and without pinholes or voids." The voids or pinholes can be filled and re-tooled with a sponge. Careful mixing of the grout combined with the lack of excess sponging should make the joints uniform in color. Note: Grouting is a technique that requires practice, this is the reason for grouting a small area at a time. If the tile you have chosen is easily scratched; it may be necessary to apply the grout to the joint alone. This can be accomplished with care using the grout float. Just be careful to not exert too much pressure on the face of the tile when using "sanded" grouts. The other option when using easily scratched tile is to use a joint size that will accommodate non-sanded grout. What if it is necessary to stop grouting and resume later on the same wall? This can be accomplished easily. It is always better to grout the entire installation at once. In this way, the chance of color variation and other problems are reduced. However, if it is mandatory to stop and resume later make sure that the grout in the finished joints is cut down to approximately 45° degrees to the substrate. Try to stop and start in an inconspicuous area as possible just in case a slight color variance does result. In this way grouting can resume and the new grout can appear flush with the existing grout. The idea is to blend the new with the old. Of course, it is also important to make sure the area is clean and that no grout residue is left on the surface of any areas before ceasing work. The grout work can then be polished using cheesecloth or towels to remove any grout haze after the grout has initially cured. If you were careful and thorough during the grouting process, the grout haze should be minimal. If there is stubborn residue, use a fiber abrasive pad, which normally does the trick. In extreme cases of grout residue, the use of specific acids can be used like sulfamic or phosphoric. The acids should not be used prior to at least 10 days after the grouting was completed. Strictly follow the Manufacturers instructions for their use. With few exceptions, Portland cement grouts should be "damp cured." In fact, ANSI a 108.10 recommends it. Use only 40-weight "Kraft" paper for this process. Do not use "poly" sheeting or roofing felt. The "poly" sheeting will accumulate water that will drip on the grouted joints and discolor them by uneven curing time. The roofing felt can have the same effect and can leave tar residue on the tile and joints. The paper is placed over the newly grouted surface and helps the grout to cure uniformly. This reduces the chance of color variance and produces a harder/denser joint. The commonly recommended curing time for Portland cement grouts is 72 hours. Let's talk about epoxy grouts. They exist in two forms; water cleanable 100% epoxy setting/grouting described under ANSI A 108.6/A 118.3 1999 and modified epoxy emulsion mortar/grout described under ANSI A 108.9/A 118.8 1999. These adhesives and grouting materials must be installed per the Manufacturers instructions. These materials, when used for grout, are applied in a similar way to that of Portland cement grouts. However, the cleanup is accomplished in a much different way. The Manufacturer will recommend a specific cleanup method for their product. Universally, the key is to allow the materials to acclimate to the room temperature in which they are to be installed for a period of 48 hours prior to their use. Remember these materials cure by chemical reaction, not hydration like Portland cement grouts. Therefore, temperature control is vital. It is recommended that they be used with a temperature range of 60-90° F. Definitely consult product literature for these parameters. Dr's Tip: It is more imperative to remove excess grouting material from the tile face with these grouts. It can be much more difficult to remove than other grouts. Plus, acids do not remove epoxy-based products. Let's talk now about a common problem associated most often with Portland cement based grouts in tile work. Efflorescence is a visible white powdery substance that is seen at times on the surface of grout joints. Efflorescence consists simply of dried salts that accumulate of the tiled surface left there by evaporating water. This salt, alkali in content, can leach up from concrete or masonry substrates. When water moves up through the tile work, it brings the salts with it. When the water evaporates the salt is left. Generally, efflorescence can be cleaned off the tile and joints by a good washing with pH balanced cleaners. In extreme cases, it can be cleaned with acid washing. As I said earlier, do not use any acids other than sulfamic or phosphoric. Absolutely use them according to the Manufacturers instructions. Remember that Portland cements are alkali based. Acid eats alkali, enough said. ********************************************************************** This message and its attachments may contain legally privileged or confidential information. If you are not the intended recipient, you must not disclose or use the information contained in it. If you have received this e-mail in error, please notify the sender immediately by return e-mail and delete the e-mail. Any content of this message and its attachments which does not relate to the official business of Eraring Energy must be taken not to have been sent or endorsed by Eraring Energy. No warranty is made that the e-mail or attachment(s) are free from computer virus or other defect. ********************************************************************** [Non-text portions of this message have been removed]
