Should you or shouldn't you? This is an area where there can be some wide variation in opinions and products. Something basically everyone agrees on is there is always an advantage to sealing unglazed tile. With contrasting colors of tile and grout, it would also be considered wise. An impregnating or penetrating sealer may be used in this application with care taken to avoid getting sealer into the grout joints. Another common application is polished or honed porcelain where small pits or pores may be present to trap grout. The cleaning process for marble, both polished and tumbled is sure to benefit when a sealer is used. Some types of slate and stone are especially absorbent and readily grab the pigmented grout.
In selection of a sealer you should make sure it would not alter the appearance of the product to which it is applied. It would be quite helpful to know what the intended floor care plan is. Occasionally you may encounter a situation where the intention is to apply a topical coating over an unglazed floor. In that case the sealer should either be part of the system or avoided. Penetrating sealers are relatively long lasting and difficult to remove. They will inhibit any attempt to bond a protective finish coat. If you are unsure of the floor care plan or are trying to prevent grout from bonding to a pitted glazed surface, such as those popular in many of the stone looks, a temporary grout release may be appropriate in that instance. Most manufactures of both grout and tile have specific recommendations. None of this is to say sealers are necessary, however, they can provide a fail-safe way to avoid film and staining.
It should only be common sense that the floor and joints should be clean prior to grouting, but common sense does not always prevail at the end of the day when grout is all the remains between you and going home or getting paid. The joints should be free of debris and any thinset squeezed up in the joist removed to 2/3 of the joint. If you are using white grout hopefully you used white thinset. A vacuum is really useful when you get done scrapping joints. Having tiled all my life, I still have to clean some joints on every job though with experience and proper setting techniques the challenge of keeping the joints thinset free does diminish. Often I hear somebody comment about not wanting to use a large notch trowel because they want to clean as little as possible. This is NOT a good reason or idea. Thinset squeezing in the joints is more about setting technique than trowel notch. One of the other helpful hints is wiping down the area to be grouted with a damp mop or sponge. Just that little effort will aid the cleaning process. If a dry surface is moistened, grout pigment is less likely to grab on the face of the tile. Now is also a good time to check the lot numbers on your grout if you have not already done so. If working from multiple lot numbers, you will want to dry blend the product prior to application.
Good tools make the job much easier. The most important tool I own for grouting is my float. You cannot believe what a difference a good grout float can make in both spreading and clean up. Recently CTEF has come into possession of several grout floats new to the market. The clean up they do on even heavily textured tile is quite impressive. All grout floats are not created equal even though many mimic a familiar green appearance. Color means nothing to performance. Another tool not seen often is a grout cleaning bucket system. If you are using a sponge and bucket to clean every job, you are working too hard. I remember when I bought my first grout cleaning bucket system. The boys in the shop thought I got suckered into another sale. It sat in the shop for quite awhile till we got on a job one day where the grout was setting a little fast. I got a call asking me to bring along the bucket and some other items to see if it would help. Long story short, by the end of the day we owned 6 of them and with little exception, never used a sponge and bucket again.
I have been part of a study for several years now on grout and thinset for a manufacturer. You cannot believe how hard this manufacturer and others work on getting consistency in their product. As part of this study they bring down products and we make panels of tile, big ones. Then, we use real world methods to apply and clean the grout. On one occasion they said they wanted us to try the latest and greatest. The only issue with the product we were informed was the need to mix thoroughly for 5 minutes instead of the 2.5 minutes we had been mixing; yes, they timed us. So, we proceeded to mix according to instructions. When we troweled it on the tile is was some of the creamiest and smoothest grout I had ever worked with. I said I think you have a winner here! Then came the news we had been duped, the only difference between that and the other grouts we were using was the mixing time, same product. Lesson learned, READ THE INSTRUCTIONS and follow them; it will make things a lot easier.
Here is where the trouble lies regardless of how good your equipment is. I understand production. I understand that grout is done at the end of the job and almost time to go home. But, next to getting enough of the right type of thinset under the tile, there is no more important part of the installation than grouting. This will determine whether your customer will have a lifetime of easy care and maintenance a lifetime of misery. This gets old but we will say it one more time, follow the instructions. If it says 2 quarts of water, use 2 quarts, not 2 1/2. Properties of the grout are greatly affected by the amount of water used. As mentioned earlier, to get the full performance of the product it must be thoroughly mixed. Slake time is not break time in spite of what your boss thinks, it is necessary to allow the mixture to completely wet out all the ingredients. If you want a creamy consistency, it cannot be done by adding water, find a product more to your liking. Adding too much water results in low compressive strength, shrinkage, effloresces, and diminished color. Low and discolored joints are typically a result of cleaning the grout to early with too much water. The grout needs to stiffen in the joint prior to clean up. If it is not stiff to the touch an excessive amount of material will be removed in the cleaning process.
Most grouts also contain powdered pigments, which are also easily removed if the hydration process is not underway. Assuming the time is right to begin we take out first pass to shape the joints and remove excess material. While it is much easier to do with a wet sponge you really need to use very little water. Something that may help on occasion is what we call "striking the joints". To use this method you take a round piece of wood with a radius appropriate to the joint width and pass it over the joints compacting them and removing excess material. This makes life much simpler if you do allow the joints to stiffen some as the excess material may be brushed away as opposed to being scrubbed away with the pigment. It will also provide a denser and uniform joint width. This is not for all jobs or all grouts, but can be a real time saver. Then comes that final cleaning. While slow and tedious, using a sponge wrung dry. I have never been able to get much more than a single pass with a hand sponge diagonal to the joints about 2 to 2 1/2 feet. If you have a secret on how to get more without having a load of residue to polish when it dries, please let me know. The one thing I have found that makes exception to the rule is a "grout bucket" set as mentioned earlier. They typically cover a larger surface area. Occasionally, it may be possible to clean with no sponge at all. This method requires either a sealed or glazed tile and just the right set of circumstances. Under this method we strike the joints, sweep the excess away and follow with rubbing the remaining residue on the tile with either burlap or a floor-scrubbing pad. This is a learned technique. We demonstrate this method in every installation class and the typical comment is it alone is worth the price of the class.
This is a very important factor in grout color, yet is the most overlooked. Inconsistent, uneven and splotchy colored cementations grout is often due to poor curing conditions. Changes in temperature of the grout installation during the installation and into the first 72 hours will cause some degree of discoloration. Differential variation in the rate of evaporation or absorption of the water in the grout due to any reason can have an effect. You should prevent, block or remove all sources that would cause uneven drying conditions for the first 72 hours. Use of natural kraft paper is often recommended to cover the installation after the grout has been cleaned from the face of the tile. Plastic sheets or newspaper should never be used to cover the tile and grout. If you do cover a floor, it is all or nothing. Covering traffic areas only will cause a darker grout color under the protection than that of the adjoining area. This includes any type of covering, even a box sitting on the floor. While rarely done, damp cure or water misting the grout at 20 - 24 hour intervals for the first 3 days will insure even drying and full hydration of the grout making it extra hard. While latex modified grouts do not require damp curing they may also benefit.
Movement joints, also called expansion joints, should be part of every tile job. These are seemingly the scourge and bane of tile setters and hated by customers. Never the less, they are a necessary evil. It is very unwise to grout in the perimeter of the room over wood or concrete. Movement between floor and wall surfaces, between adjoining walls, at ceiling junctures, between countertops and backsplashes and between tiles and all other hard objects they may come up against is to be expected. Since there is going to be movement, each tile installation needs to provide space for this to happen. These expansion or movement joints and allow a certain amount of motion to occur naturally without damaging any of the tile installation. Instead of being filled with grout, they should be left open or filled with a resilient caulk or sealant. Nearly invisible movement joints can be made by using one of many color-matched caulks, some even available with fine grains of sand to duplicate the texture and of real grout. The one drawback of using caulks or sealant in these areas is it may have to be restored from time to time but this is a small price to pay to keep the tile installation intact.
One thing is certain, all building materials move. To have a successful ceramic tile installation, tile must not only be firmly supported, but be able provide for the expected movement of the structure. Thinbed installation systems of today are much less forgiving than the traditional mortar bed methods of days past. Buildings are being built faster with many engineered products as opposed to massive beams, boards, and slabs of yesterday. Numerous ceramic tile installation systems have been designed to support these trends but often provide a very narrow margin of error given their own highly engineered nature. It is quite possible that an end user may chose to ignore the need for joints due to aesthetics. If that decision is made on the facts so be it, but I hope you have it in writing, as they tend to forget when the floor comes apart.
Sealing the Grout
Sealing the grout is a helpful addition to a cement grout installation. However, it is a maintenance item not commonly part of the grout installation. Sealing greatly improves the resistance of the grout to staining and discoloration and provides an aid to the overall maintenance. It provides what some call "reaction time" to wipe up spills without causing staining. It does not make grout waterproof or stain proof. Many times questions occur about the cure time required before sealing the grout and what type of sealer should be used on the grout. Different answers are applied to different products. There is no universal recommendation due the chemical variation of the products. Penetrating sealers are absorbed into the minute pores of unglazed tile and grout. They are usually composed of silicone or latex solids suspended in a mineral spirits or water carrier. After application, the carrier evaporates and leaves the solid material within the tile and grout which fills up the pores and close capillaries to the surface thereby reducing absorption of potentially staining materials. There is no such thing as self-cleaning grout. As soon as customers hear stain resistant or stain proof they think no cleaning. If you get involved with sealers you will have happier customers by providing factual information on the products.